(en)A process is provided for producing target concentrations of peroxycarboxylic acids from carboxylic acid esters. More specifically, carboxylic acid esters are reacted with an inorganic peroxide, such as hydrogen peroxide, in the presence of an enzyme catalyst having perhydrolysis activity under conditions where control of reaction pH by selection of buffer concentration and concentration of perhydrolase and reactants produces a targeted concentration of peroxycarboxylic acids. The present perhydrolase catalysts are classified as members of the carbohydrate esterase family 7 (CE-7) based on the conserved structural features. Further, disinfectant formulations comprising the peracids produced by the processes described herein are provided, as are corresponding methods of use.

1.ApplicationNumber: US-201213354486-A
1.PublishNumber: US-2012122979-A1
2.Date Publish: 20120517
3.Inventor: DICOSIMO ROBERT
PAYNE MARK SCOTT
HANN EUGENIA COSTA

4.Inventor Harmonized: DICOSIMO ROBERT(US)
PAYNE MARK SCOTT(US)
HANN EUGENIA COSTA(US)

5.Country: US
6.Claims:
(en)A process is provided for producing target concentrations of peroxycarboxylic acids from carboxylic acid esters. More specifically, carboxylic acid esters are reacted with an inorganic peroxide, such as hydrogen peroxide, in the presence of an enzyme catalyst having perhydrolysis activity under conditions where control of reaction pH by selection of buffer concentration and concentration of perhydrolase and reactants produces a targeted concentration of peroxycarboxylic acids. The present perhydrolase catalysts are classified as members of the carbohydrate esterase family 7 (CE-7) based on the conserved structural features. Further, disinfectant formulations comprising the peracids produced by the processes described herein are provided, as are corresponding methods of use.

7.Description:
(en)This application claims the benefit of U.S. Provisional Patent Application No. 61/088,673, filed Aug. 13, 2008 and U.S. Provisional Patent Application No. 61/102,520, filed Oct. 3, 2008, both of which are incorporated by reference herein in their entireties.


FIELD OF THE INVENTION
This invention relates to the field of peracid biosynthesis and in situ enzyme catalysis. Specifically, a process is provided to control the production of peracids generated by the perhydrolysis activity of enzymes identified structurally as belonging to the CE-7 family of carbohydrate esterases, including cephalosporin acetyl hydrolases (CAHs; E.C. 3.1.1.41) and acetyl xylan esterases (AXEs; E.C. 3.1.1.72). The enzymatic process produces percarboxylic acids from carboxylic acid ester substrates. Elucidation of the specific activity versus pH profile of the reaction allows control of the reaction by varying parameters including buffer concentration and pH. Disinfectant formulations comprising the peracids produced by the processes described herein are provided.
BACKGROUND OF THE INVENTION
Peracid compositions have been reported to be effective antimicrobial agents. Methods to clean, disinfect, and/or sanitize hard surfaces, meat products, living plant tissues, and medical devices against undesirable microbial growth have been described (U.S. Pat. No. 6,545,047; U.S. Pat. No. 6,183,807; U.S. Pat. No. 6,518,307; U.S. patent application publication 20030026846; and U.S. Pat. No. 5,683,724). Peracids have also been reported to be useful in preparing bleaching compositions for laundry detergent applications (U.S. Pat. No. 3,974,082; U.S. Pat. No. 5,296,161; and U.S. Pat. No. 5,364,554).
Peracids can be prepared by the chemical reaction of a carboxylic acid and hydrogen peroxide (see Organic Peroxides , Daniel Swern, ed., Vol. 1, pp 313-516; Wiley Interscience, New York, 1971). The reaction is usually catalyzed by a strong inorganic acid, such as concentrated sulfuric acid. The reaction of hydrogen peroxide with a carboxylic acid is an equilibrium reaction, and the production of peracid is favored by the use of an excess concentration of peroxide and/or carboxylic acid, or by the removal of water.
Enzyme catalysts can also catalyze the rapid production of peracid at the time of use and/or application, avoiding the need for storage of peracid solutions, which may cause peracid concentration to decrease over time. The high concentrations of carboxylic acids typically used to produce peracid via the direct chemical reaction with hydrogen peroxide are not required for enzymatic production of peracid, where the enzyme-catalyzed reaction can use a carboxylic acid ester as substrate at a much lower concentration than is typically used in the chemical reaction. The enzyme-catalyzed reaction can be performed across a broad range of pH, depending on enzyme activity and stability at a given pH, and on the substrate specificity for perhydrolysis at a given pH.
Esterases, lipases and some proteases have the ability to catalyze the hydrolysis of alkyl esters to produce the corresponding carboxylic acids (Formula 1):









Some esterases, lipases, and proteases also exhibit perhydrolysis activity, catalyzing the synthesis of peracids from alkyl esters (Formula 2):









The CE-7 class of carbohydrate esterases has been found to have highly specific activity for perhydrolysis of esters, particularly acetyl esters of alcohols, diols and glycerols. U.S. patent application Ser. Nos. 11/638,635; 11/743,354; 11/943,872; and 12/143,375 to DiCosimo et al. disclose enzymes structurally classified as members of the CE-7 family of carbohydrate esterases (e.g., cephalosporin C deacetylases [CAHs] and acetyl xylan esterases [AXEs]) that are characterized by significant perhydrolysis activity for converting carboxylic acid esters (in the presence of a suitable source of peroxygen, such as hydrogen peroxide) into peroxycarboxylic acids at concentrations sufficient for use as a disinfectant and/or a bleaching agent. Under certain reaction conditions, CE-7 esterases can catalyze the production of concentrations of peracid at least as high as 4000-5000 ppm in 1 min and up to at least 9000 ppm in 5 min to 30 min (U.S. patent application Ser. No. 12/143,375 to DiCosimo et al.). Peroxycarboxylic acids can be corrosive to certain metal surfaces, however, so it may be desirable to limit the total amount of peracid produced during the reaction to prevent or minimize the corrosive effect of the resulting solution. For example, applications that require production of no more than 200 ppm to 1000 ppm of peracid in 1 minute often employ reaction conditions that yield a final concentration of peracid well above these limits. In an application for in situ generation of peracid for disinfection of hard surfaces, it is desirable to have the ability to rapidly generate the desired concentration of peracid without significantly exceeding the upper efficacious disinfectant concentration, thereby limiting or preventing the corrosion of certain components of the surface. In an application for in situ generation of peracid for bleaching of laundry or textiles, similar limitations to the concentration of peracid generated above that required for bleaching are also desirable.
In addition to catalyzing the production of peracids, CE-7 esterases can also catalyze the hydrolysis of peracid to produce carboxylic acid and hydrogen peroxide. Therefore, under reaction conditions where the enzyme retains its activity for an extended period of time, it may destroy the peracid produced in the first enzyme-catalyzed reaction of ester and peroxide, producing carboxylic acid (e.g., acetic acid) as a byproduct that can impart an undesirable odor to the disinfectant solution. This peracid hydrolysis activity of the enzyme could also jeopardize the long term stability of peracid-containing formulations produced by CE-7 esterases over the course of several hours, or even several days or weeks, depending on the stability of the peracid in the disinfectant formulation.
Peracid solutions have a wide variety of applications. Though progress has been made in devising efficient and effective ways to produce peracid solutions, improved methods are needed. An in situ process for producing peracids that limits the enzyme-catalyzed production of peracids in a peracid concentration-dependent manner would allow targeted concentrations of peracids to be produced in a task-appropriate way.
SUMMARY OF THE INVENTION
Disclosed herein are enzyme-catalyzed processes of producing a target concentration of peracid. The enzyme-catalyzed production of peracids is limited in a peracid concentration-dependent manner. Also disclosed herein are processes of disinfecting surfaces or inanimate objects, and of bleaching of textiles or laundry, through the use of peracid-containing solutions that deliver a targeted concentration of peracid. The described processes are enabled by the first discovery that enzymes belonging to the structural family of CE-7 esterases (e.g., cephalosporin C deacetylases [CAHs] and acetyl xylan esterases [AXEs]) exhibit significant perhydrolysis activity for converting carboxylic acid esters into peracids, and by the second discovery that the activity of said enzymes for both perhydrolysis of esters to produce peracids and for hydrolysis of peracids to produce carboxylic acids and hydrogen peroxide decreases significantly or is inactivated as the pH of the reaction decreases over the course of the reaction that produces peracid and/or carboxylic acid. The activity of the CE-7 esterases for production of peracid, and optionally for hydrolysis of peracid, may be controlled by a number of methods, including but not limited to selecting the initial pH of the reaction, or by selecting the buffer and buffer concentration in the perhydrolysis reaction, or by a combination of selection of initial pH and buffer and buffer concentration, such that a targeted concentration of peracid, or targeted range of peracid concentration, is produced.
In one embodiment, the processes provide a means for producing enzyme-catalyzed peracid solutions having peracid concentrations sufficient to disinfect surfaces or inanimate objects and also reduce or prevent the corrosive effects associated with higher concentrations of peracid in solution. In a second embodiment, the processes provide a means for producing enzyme-catalyzed peracid solutions having peracid concentrations sufficient to disinfect or remove stains from textiles or laundry and also reduce or prevent the damaging effects associated with higher concentrations of peracid in solution towards dyed textiles or clothing, or damaging effects associated with fabric integrity. In some embodiments the processes provide a means for producing enzyme-catalyzed peracid solutions suitable to disinfect surfaces or inanimate objects where the duration of the enzymatic activity is insufficient to mediate a substantial secondary enzyme-catalyzed hydrolysis of the peracid produced in the initial enzyme-catalyzed reaction, where the secondary enzyme-catalyzed hydrolysis of the peracid yields a carboxylic acid (e.g., acetic acid).
One way to control the amount of peracid produced by the enzyme-catalyzed reaction is to use reaction conditions that selectively reduce, or inactivate, the catalytic function of the enzyme. The catalytic activity of perhydrolase enzymes can be controlled in a number of ways, such as altering the pH of the reaction mixture. Accordingly, the initial pH of the reaction mixture may be adjusted such that the pH of the reaction decreases as peracid is produced, ultimately resulting in the reaction mixture having a pH at which the enzyme activity is significantly reduced or inactivated. Alternatively, when only low concentrations of peracid are desirable, the initial pH of the reaction can be low enough to substantially reduce enzyme activity, resulting in only a very short period of enzyme-catalyzed peracid production. Another way to control the amount of peracid produced by the enzyme-catalyzed reaction is to employ a buffer concentration in the reaction mixture such that its buffering capacity is limited, causing the buffer to be quickly exhausted as peracid and other reaction products (e.g., carboxylic acid) are produced, and thereby reducing the pH of the reaction mixture and reducing, or inactivating, enzyme activity. One way to control the amount of peracid produced by an enzyme-catalyzed reaction is to select a reaction mixture initial pH and a buffer with a pKa that will cause the pH of the reaction mixture to decrease such that the enzymatic activity of the reaction is reduced or inactivated as the desired amount of peracid is produced. Another approach is to use a pH-sensitive enzyme with a high catalytic rate to produce a reaction with a high initial output of peracid that causes the pH of the reaction mixture to decrease to a point at which catalytic activity is significantly decreased or inactivated. Each of these approaches, however, requires selecting an enzyme for use in the reaction that has pH-sensitive catalytic activity, such that the ability of the enzyme to catalyze the production of peracid is eliminated, or substantially reduced, when the reaction mixture reaches a desired pH. In addition, the specific activity versus reaction pH profile of the enzyme must be understood in order to design perhydrolysis reactions that produce targeted amount of peracid. Described herein are pH-sensitive perhydrolase enzymes and methods of producing targeted concentrations of peracid in a fixed period of time.
Described are aqueous peracid solutions that maintain a relatively stable concentration of peracid, i.e., within about 20% of a target peracid concentration, following pH-mediated reduction, or inactivation, of enzyme catalyst activity. In some preferred embodiments, aqueous peracid solutions that maintain a peracid concentration within about 15% of a target peracid concentration, and more preferably within about 10% of a target peracid concentration, following pH-mediated reduction, or inactivation, of enzyme catalyst activity are provided. The stability of the peracid concentration can persist for hours after the reduction, or inactivation, of the enzyme-catalyzed production of peracid. In one embodiment, the peracid concentration is stable for about 3 hours, about 6 hours, about 9 hours, about 12 hours, about 15 hours, about 18 hours, about 21 hours, about 24 hours, about 30 hours, about 36 hours, about 42 hours, or about 48 hours after the enzyme-catalyzed production of peracid has ceased.
Specific examples of perhydrolases are exemplified from Bacillus subtilis (ATCC® 31954™), B. subtilis BE1010 (Payne and Jackson, J. Bacteriol. 173:2278-2282 (1991)), B. subtilis ATCC® 6633™ (U.S. Pat. No. 6,465,233), B. subtilis ATCC® 29233™; B. licheniformis ATCC® 14580™ (Rey et al., Genome Biol., 5(10):article 77 (2004)), Clostridium thermocellum ATCC®27405™ (Copeland et al., GENBANK® ZP — 00504991, B. pumilus PS213 (Degrassi et al., Microbiology, 146:1585-1591 (2000)), Thermotoga neapolitana (GENBANK® AAB70869.1), Bacillus clausii KSM-K16 (GENBANK® YP — 175265), Bacillus sp. NRRL B-14911 (GENBANK® ZP — 01168674), Bacillus halodurans C-125 (GENBANK® NP 244192), Thermoanaerobacterium sp. JW/SL YS485 (GENBANK® AAB68821), Bacillus subtilis subsp. subtilis str. 168 (GENBANK® NP — 388200), Thermotoga maritima MSB8 (GENBANK® NP — 227893.1), Thermoanaerobacterium saccharolyticum (GENBANK® S41858), Thermotoga lettingae (GENBANK® CP000812), Thermotoga petrophila (GENBANK® CP000702), and Thermotoga sp. RQ2 (GENBANK® CP000969).
Each of the present perhydrolase enzymes described herein share conserved structural features (i.e., a conserved signature motif) as well as superior perhydrolysis activity relative to other α/β-hydrolases, which makes this family of enzymes particularly suitable for generating peracids in situ at concentrations sufficient for use as a disinfectant and/or bleaching agent. Suitable perhydrolases useful in the present process can be identified by a conserved signature motif found within the CE-7 family of carbohydrate esterases.
Provided herein is a process for producing a target concentration of peroxycarboxylic acid comprising:
a. selecting a set of reaction components to produce a target concentration of peroxycarboxylic acid, said reaction components comprising:
1) at least one:
i) ester having the structure



[X] m R 5 wherein X is an ester group of the formula R 6 C(O)O R 6 is a C1 to C7 linear, branched or cyclic hydrocarbyl moiety, optionally substituted with hydroxyl groups or C1 to C4 alkoxy groups, wherein R 6 optionally comprises one or more ether linkages when R 6 is C2 to C7; R 5 is a C1 to C6 linear, branched, or cyclic hydrocarbyl moiety optionally substituted with hydroxyl groups; wherein each carbon atom in R 5 individually comprises no more than one hydroxyl group or no more than one ester group; wherein R 5 optionally comprises one or more ether linkages; m is an integer from 1 to the number of carbon atoms in R 5; said ester having a solubility in water of at least 5 parts per million at 25° C.; or ii) glyceride having the structure















wherein R 1 is C1 to C7 straight chain or branched chain alkyl optionally substituted with an hydroxyl or a C1 to C4 alkoxy group and R 3 and R 4 are individually H or R 1 C(O); or
iii) acetylated monosaccharide, acetylated disaccharide, or acetylated polysaccharide;
or mixtures thereof;


2) a source of peroxygen;
3) an enzyme catalyst having perhydrolysis activity, wherein said enzyme catalyst comprises an enzyme having a CE-7 signature motif that aligns with a reference sequence SEQ ID NO: 2 using CLUSTALW, said signature motif comprising:
i) an RGQ motif at amino acid positions 118-120 of SEQ ID NO:2; ii) a GXSQG motif at amino acid positions 179-183 of SEQ ID NO:2; and iii) an HE motif at amino acid positions 298-299 of SEQ ID NO:2; and

wherein said enzyme comprises at least 30% amino acid identity to SEQ ID NO: 2; and
4) optionally at least one buffer; and


b. combining the selected set of reaction components under aqueous reaction conditions to form a reaction mixture; whereby reaction products are formed comprising peroxycarboxylic acid; wherein the reaction products comprising peroxycarboxylic acid reduce the reaction mixture pH to less than about 6.0 within about 1 minute to about 10 minutes of combining the reaction components and produce the target concentration of peroxycarboxylic acid; wherein the reduction in the reaction mixture pH is used to control the target concentration of peroxycarboxylic acid produced.




Also provided herein is a process for disinfecting a hard surface or inanimate object by producing a target concentration of peroxycarboxylic acid comprising:
a. selecting a set of reaction components to produce a target concentration of peroxycarboxylic acid, said reaction components comprising:
1) at least one:
i) ester having the structure



[X] m R 5 wherein X is an ester group of the formula R 6 C(O)O
R 6 is a C1 to C7 linear, branched or cyclic hydrocarbyl moiety, optionally substituted with hydroxyl groups or C1 to C4 alkoxy groups, wherein R 6 optionally comprises one or more ether linkages when R 6 is C2 to C7; R 5 is a C1 to C6 linear, branched, or cyclic hydrocarbyl moiety optionally substituted with hydroxyl groups; wherein each carbon atom in R 5 individually comprises no more than one hydroxyl group or no more than one ester group; wherein R 5 optionally comprises one or more ether linkages; m is an integer from 1 to the number of carbon atoms in R 5 ;
said ester having a solubility in water of at least 5 parts per million at 25° C.; or ii) glyceride having the structure















wherein R 1 is C1 to C7 straight chain or branched chain alkyl optionally substituted with an hydroxyl or a C1 to C4 alkoxy group and R 3 and R 4 are individually H or R 1 C(O); or
iii) acetylated monosaccharide, acetylated disaccharide, or acetylated polysaccharide;
or mixtures thereof;


2) a source of peroxygen;
3) an enzyme catalyst having perhydrolysis activity, wherein said enzyme catalyst comprises an enzyme having a CE-7 signature motif that aligns with a reference sequence SEQ ID NO: 2 using CLUSTALW, said signature motif comprising:
i) an RGQ motif at amino acid positions 118-120 of SEQ ID NO:2; ii) a GXSQG motif at amino acid positions 179-183 of SEQ ID NO:2; and iii) an HE motif at amino acid positions 298-299 of SEQ ID NO:2; and wherein said enzyme comprises at least 30% amino acid identity to SEQ ID NO: 2; and

4) optionally at least one buffer;


b. combining the selected set of reaction components under aqueous reaction conditions to form a reaction mixture; whereby reaction products are formed comprising peroxycarboxylic acid; wherein the reaction products comprising peroxycarboxylic acid reduce the reaction mixture pH to less than about 6.0 within about 1 minute to about 10 minutes of combining the reaction components and produce the target concentration of peroxycarboxylic acid; wherein the reduction in the reaction mixture pH is used to control the target concentration of peroxycarboxylic acid produced; and
c. applying the peroxycarboxylic acid produced in step (b) to a hard surface or inanimate object.




In some embodiments, the peroxycarboxylic acid produced is diluted.
In another embodiment, the catalyst is a substantially similar enzyme having an amino acid sequence at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identical to one or more amino acid sequences selected from the group consisting of SEQ ID NO: 2, SEQ ID NO: 4, SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 10, SEQ ID NO: 12, SEQ ID NO: 14, SEQ ID NO: 16, SEQ ID NO: 18, SEQ ID NO: 20, SEQ ID NO: 22, SEQ ID NO: 24, SEQ ID NO: 30, SEQ ID NO: 54, SEQ ID NO: 56, SEQ ID NO: 58, SEQ ID NO: 60, and SEQ ID NO: 62.
In another embodiment, the perhydrolase catalyst comprises an enzyme having an amino acid sequence encoded by a nucleic acid molecule that hybridizes to a nucleic acid sequence selected from the group consisting of SEQ ID NO: 1; SEQ ID NO: 3; SEQ ID NO: 5, SEQ ID NO: 7, SEQ ID NO: 9, SEQ ID NO: 11, SEQ ID NO: 13, SEQ ID NO: 15, SEQ ID NO: 17, SEQ ID NO: 19, SEQ ID NO: 21, SEQ ID NO: 23, SEQ ID NO: 29, SEQ ID NO: 55, SEQ ID NO: 57, SEQ ID NO: 59, and SEQ ID NO: 61 under stringent hybridization conditions. In a preferred embodiment, the present invention includes an enzyme having perhydrolase activity encoded by isolated nucleic acid molecule that hybridizes under stringent conditions to a nucleic acid molecule having a nucleic acid sequence selected from the group consisting of SEQ ID NO: 1, SEQ ID NO: 9, SEQ ID NO: 13, and SEQ ID NO: 15.
In another embodiment, the perhydrolase catalyst comprises a variant Thermotoga enzyme having at least 95% amino acid sequence identity (or, in various embodiments, 96%, 97%, 98%, or 99% sequence identity), based on the CLUSTAL method of alignment (such as CLUSTALW) with pairwise alignment default parameters of KTUPLE=1, GAP PENALTY=3, WINDOW=5 and DIAGONALS SAVED=5, when compared to SEQ ID NOs: 69, 70, 71, 72, or 73, provided that a substitution to amino acid 277 of SEQ ID NOs: 69, 70, 71, 72, or 73 is selected from the group consisting of serine, threonine, valine, and alanine.
In another embodiment, the perhydrolase catalyst comprises a variant Thermotoga enzyme comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 69, 70, 71, 72, and 73 provided the amino acid residue 277 is selected from the group consisting of serine, threonine, valine, and alanine.
In a specific embodiment, the perhydrolase catalyst comprises a variant Thermotoga neapolitana enzyme comprising amino acid sequence SEQ ID NO: 69 wherein amino acid residue 277 is substituted with an amino acid selected from the group consisting of serine, threonine, valine, and alanine.
In a further specific embodiment, the perhydrolase catalyst is a variant Thermotoga maritima enzyme comprising amino acid sequence SEQ ID NO: 70 wherein amino acid residue 277 is substituted with an amino acid selected from the group consisting of serine, threonine, valine, and alanine.
In some aspects, the aqueous reaction mixture includes a buffer and has a specific initial pH. The buffer may be any buffer suitable for carrying out an enzymatic perhydrolysis reaction at the desired pH. In some aspects, the buffer is selected from the group consisting of the sodium salt, the potassium salt or mixed sodium and potassium salts of bicarbonate buffer, citrate buffer, methylphosphonate buffer, pyrophosphate buffer and phosphate buffer. In some aspects, the buffer is bicarbonate buffer or citrate buffer. In some aspects, the reaction mixture containing a buffer has an initial pH of about 5.5 to about 8.5. In some aspects, the reaction mixture containing a buffer has an initial pH of about 8.5. In some aspects, the reaction mixture containing a buffer has an initial pH of about 8.1. In some aspects, the reaction mixture containing a buffer has an initial pH of about 7.2. In some aspects, the reaction mixture containing a buffer has an initial pH of about 6.5. In some aspects, the reaction mixture containing a buffer has an initial pH of about 6.0. In some aspects, the reaction mixture containing a buffer has an initial pH of about 5.5.
In some aspects, the buffer included in the aqueous reaction mixture can establish the initial pH of the mixture. In some aspects, the buffer produces an aqueous reaction mixture with an initial pH of about 5.5 to about 8.5. In some aspects, the buffer produces an aqueous reaction mixture with an initial pH of about 8.1. In some aspects, the buffer produces an aqueous reaction mixture with an initial pH of about 7.2. In some aspects, the buffer produces an aqueous reaction mixture with an initial pH of about 6.5. In some aspects, the buffer produces an aqueous reaction mixture with an initial pH of about 6.0. In some aspects, the buffer produces an aqueous reaction mixture with an initial pH of about 5.5.
In some aspects, the aqueous reaction mixture may include at least one buffer having a specific concentration. The buffer may be any buffer suitable for carrying out an enzymatic perhydrolysis reaction. In some aspects, the reaction mixture contains buffer at a concentration of about 0.01 mM to about 200 mM. In some aspects, the reaction mixture contains buffer at a concentration of about 50 mM. In some aspects, the reaction mixture contains buffer having a concentration of about 25 mM to about 0.1 mM. In some aspects, the reaction mixture contains bicarbonate buffer having a concentration of about 25 mM to about 0.1 mM. In some aspects, the reaction mixture contains buffer having a concentration of less than about 5 mM. In some aspects, the reaction mixture contains bicarbonate buffer having a concentration of less than about 5 mM.
In a preferred embodiment, the substrate is selected from the group consisting of monoacetin; diacetin; triacetin; monopropionin; dipropionin; tripropionin; monobutyrin; dibutyrin; tributyrin; glucose pentaacetate; xylose tetraacetate; acetylated xylan; acetylated xylan fragments; β-D-ribofuranose-1,2,3,5-tetraacetate; tri-O-acetyl-D-galactal; tri-O-acetyl-glucal; monoesters or diesters of 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 2,5-pentanediol, 1,6-pentanediol, 1,2-hexanediol, 2,5-hexanediol, 1,6-hexanediol; and mixtures thereof.
BRIEF DESCRIPTION OF THE BIOLOGICAL SEQUENCES
The following sequences comply with 37 C.F.R. 1.821-1.825 (“Requirements for Patent Applications Containing Nucleotide Sequences and/or Amino Acid Sequence Disclosures—the Sequence Rules”) and are consistent with World Intellectual Property Organization (WIPO) Standard ST.25 (1998) and the sequence listing requirements of the European Patent Convention (EPC) and the Patent Cooperation Treaty (PCT) Rules 5.2 and 49.5(a-bis), and Section 208 and Annex C of the Administrative Instructions. The symbols and format used for nucleotide and amino acid sequence data comply with the rules set forth in 37 C.F.R. §1.822.
SEQ ID NO: 1 is the nucleic acid sequence of the cephalosporin C deacetylase (cah) coding region from Bacillus subtilis ATCC® 31954T″.
SEQ ID NO: 2 is the deduced amino acid sequence of the cephalosporin C deacetylase from Bacillus subtilis ATCC® 31954™.
SEQ ID NO: 3 is the nucleic acid sequence of the cephalosporin C deacetylase coding region from B. subtilis subsp. subtilis str. 168.
SEQ ID NO: 4 is the deduced amino acid sequence of the cephalosporin C deacetylase from B. subtilis subsp. subtilis str. 168, and is identical to the deduced amino acid sequence of the cephalosporin C deacetylase from B. subtilis BE1010.
SEQ ID NO: 5 is the nucleic acid sequence of the cephalosporin acetylesterase coding region from B. subtilis ATCC® 6633™.
SEQ ID NO: 6 is the deduced amino acid sequence of the cephalosporin acetylesterase from B. subtilis ATCC® 6633™.
SEQ ID NO: 7 is the nucleic acid sequence of the cephalosporin C deacetylase coding region from B. licheniformis ATCC® 14580™.
SEQ ID NO: 8 is the deduced amino acid sequence of the cephalosporin C deacetylase from B. licheniformis ATCC® 14580™.
SEQ ID NO: 9 is the nucleic acid sequence of the acetyl xylan esterase coding region from B. pumilus PS213.
SEQ ID NO: 10 is the deduced amino acid sequence of the acetyl xylan esterase from B. pumilus PS213.
SEQ ID NO: 11 is the nucleic acid sequence of the acetyl xylan esterase coding region from Clostridium thermocellum ATCC® 27405™.
SEQ ID NO: 12 is the deduced amino acid sequence of the acetyl xylan esterase from Clostridium thermocellum ATCC® 27405™.
SEQ ID NO: 13 is the nucleic acid sequence of the acetyl xylan esterase coding region from Thermotoga neapolitana.
SEQ ID NO: 14 is the deduced amino acid sequence of the acetyl xylan esterase from Thermotoga neapolitana.
SEQ ID NO: 15 is the nucleic acid sequence of the acetyl xylan esterase coding region from Thermotoga maritima MSB8.
SEQ ID NO: 16 is the deduced amino acid sequence of the acetyl xylan esterase from Thermotoga maritima MSB8.
SEQ ID NO: 17 is the nucleic acid sequence of the acetyl xylan esterase coding region from Thermoanaerobacterium sp. JW/SL YS485.
SEQ ID NO: 18 is the deduced amino acid sequence of the acetyl xylan esterase from Thermoanaerobacterium sp. JW/SL YS485.
SEQ ID NO: 19 is the nucleic acid sequence of the cephalosporin C deacetylase coding region from Bacillus sp. NRRL B-14911.
SEQ ID NO: 20 is the deduced amino acid sequence of the cephalosporin C deacetylase from Bacillus sp. NRRL B-14911.
SEQ ID NO: 21 is the nucleic acid sequence of the cephalosporin C deacetylase coding region from Bacillus halodurans C-125.
SEQ ID NO: 22 is the deduced amino acid sequence of the cephalosporin C deacetylase from Bacillus halodurans C-125.
SEQ ID NO: 23 is the nucleic acid sequence of the cephalosporin C deacetylase coding region from Bacillus clausii KSM-K16.
SEQ ID NO: 24 is the deduced amino acid sequence of the cephalosporin C deacetylase from Bacillus clausii KSM-K16.
SEQ ID NOs: 25 and 26 are primers used to PCR amplify perhydrolase genes from Bacillus subtilis species for construction of pSW194 and pSW189.
SEQ ID NO: 27 is the nucleic acid sequence of the PCR product cloned into pSW194.
SEQ ID NO: 28 is the nucleic acid sequence of the PCR product cloned into pSW189.
SEQ ID NO: 29 is the nucleic acid sequence of the Bacillus subtilis ATCC® 29233™ cephalosporin C deacetylase (cah) gene.
SEQ ID NO: 30 is the deduced amino acid sequence of the Bacillus subtilis ATCC® 29233™ cephalosporin C deacetylase (CAH).
SEQ ID NOs: 31 and 32 are primers used to PCR amplify the Bacillus licheniformis ATCC® 14580™ cephalosporin C deacetylase gene for construction of pSW191.
SEQ ID NOs: 33 and 34 are primers used to PCR amplify the Bacillus pumilus PS213 acetyl xylan esterase coding sequence (GENBANK® AJ249957) for construction of pSW195.
SEQ ID NO: 35 is the nucleic acid sequence of the kanamycin resistance gene.
SEQ ID NO 36 is the nucleic acid sequence of plasmid pKD13.
SEQ ID NOs: 37 and 38 are primers used to generate a PCR product encoding the kanamycin gene flanked by regions having homology to the katG catalase gene in E. coli MG1655. The product was used to disrupt the endogenous katG gene.
SEQ ID NO: 39 is the nucleic acid sequence of the PCR product encoding the kanamycin resistance gene flanked by regions having homology to the katG catalase gene in E. coli MG1655. The product was used to disrupt the endogenous katG gene.
SEQ ID NO: 40 is the nucleic acid sequence of the katG catalase gene in E. coli MG1655.
SEQ ID NO: 41 is the deduced amino acid sequence of the KatG catalase in E. coli MG1655.
SEQ ID NO: 42 is the nucleic acid sequence of plasmid pKD46.
SEQ ID NOs: 43 and 44 are primers used to confirm the disruption of the katG gene.
SEQ ID NO: 45 is the nucleic acid sequence of plasmid pCP20.
SEQ ID NOs: 46 and 47 are primers used to generate a PCR product encoding the kanamycin gene flanked by regions having homology to the katE catalase gene in E. coli MG1655. The product was used to disrupt the endogenous katE gene.
SEQ ID NO: 48 is the nucleic acid sequence of the PCR product encoding the kanamycin resistance gene flanked by regions having homology to the katE catalase gene in E. coli MG1655. The product was used to disrupt the endogenous katE gene.
SEQ ID NO: 49 is the nucleic acid sequence of the katE catalase gene in E. coli MG1655.
SEQ ID NO: 50 is the deduced amino acid sequence of the KatE catalase in E. coli MG1655.
SEQ ID NOs: 51 and 52 are primers used to confirm disruption of the katE gene in the single knockout strain E. coli MG1655 ΔkatE, and in the double-knockout strain E. coli MG1655 ΔkatG ΔkatE, herein referred to as E. coli KLP18.
SEQ ID NO: 53 is the amino acid sequence of the region encompassing amino acids residues 118 through 299 of SEQ ID NO: 2.
SEQ ID NO: 54 is the deduced amino acid sequence of the acetyl xylan esterase from Thermoanaerobacterium saccharolyticum (GENBANK® Accession No. S41858).
SEQ ID NO: 55 is the nucleic acid sequence of the acetyl xylan esterase coding region from Thermotoga lettingae.
SEQ ID NO: 56 is the deduced amino acid sequence of the acetyl xylan esterase from Thermotoga lettingae.
SEQ ID NO: 57 is the nucleic acid sequence of the acetyl xylan esterase coding region from Thermotoga petrophila.
SEQ ID NO: 58 is the deduced amino acid sequence of an acetyl xylan esterase from Thermotoga petrophila.
SEQ ID NO: 59 is the nucleic acid sequence of the acetyl xylan esterase coding region from Thermotoga sp. RQ2 identified herein as “RQ2(a)”.
SEQ ID NO: 60 is the deduced amino acid sequence of an acetyl xylan esterase (GENBANK® Accession No. ACB09222) from Thermotoga sp. RQ2 identified herein as “RQ2(a)”.
SEQ ID NO: 61 is the nucleic acid sequence of the acetyl xylan esterase coding region from Thermotoga sp. RQ2 identified herein as “RQ2(b)”.
SEQ ID NO: 62 is the deduced amino acid sequence of an acetyl xylan esterase (GENBANK® Accession No. ACB08860) from Thermotoga sp. RQ2 identified herein as “RQ2(b)”.
SEQ ID NOs: 63 and 64 are primers used to PCR amplify the Thermotoga maritima MSB8 acetyl xylan esterase gene (GENBANK accession #NP — 227893.1).
SEQ ID NO: 65 is the PCR amplified nucleic acid sequence of the Thermotoga maritima MSB8 acetyl xylan esterase used to generate pSW207.
SEQ ID NOs: 66 and 67 are primers used to PCR amplify the Thermotoga neapolitana acetyl xylan esterase gene (GENBANK® 58632) for construction of pSW196.
SEQ ID NO: 68 is the nucleic acid sequence of the codon-optimized version of the Thermotoga neapolitana acetyl xylan esterase gene in plasmid pSW196.
SEQ ID NO: 69 represents the deduced amino acid sequence of the acetyl xylan esterase variants derived from the wild-type sequence of an acetyl xylan esterase from Thermotoga neapolitana , where the Xaa residue at position 277 is Ala, Val, Ser, or Thr.
SEQ ID NO: 70 represents the deduced amino acid sequence of the acetyl xylan esterase variants derived from the wild-type sequence of an acetyl xylan esterase from Thermotoga maritima MSB8, where the Xaa residue at position 277 is Ala, Val, Ser, or Thr.
SEQ ID NO: 71 represents the deduced amino acid sequence of the acetyl xylan esterase variants derived from the wild-type sequence of an acetyl xylan esterase from Thermotoga lettingae , where the Xaa residue at position 277 is Ala, Val, Ser, or Thr.
SEQ ID NO: 72 represents the deduced amino acid sequence of the acetyl xylan esterase variants derived from the wild-type sequence of an acetyl xylan esterase from Thermotoga petrophila , where the Xaa residue at position 277 is Ala, Val, Ser, or Thr.
SEQ ID NO: 73 represents the deduced amino acid sequence of the acetyl xylan esterase variants derived from the wild-type sequence of an acetyl xylan esterase from Thermotoga sp. RQ2 described herein as “RQ2(a)”, where the Xaa residue at position 277 is Ala, Val, Ser, or Thr.


DETAILED DESCRIPTION
The stated problems have been solved by the discovery that enzymes belonging to the CE-7 carbohydrate esterase family exhibit significant perhydrolysis activity for converting carboxylic acid ester substrates to peracids that can be regulated by controlling the pH of the reaction mixture. Elucidation of the specific activity versus pH profile of CE-7 carbohydrate esterases allows for the control of enzyme-driven production of peracids by varying reaction parameters including buffer concentration and pH. Having this understanding, this family of structurally related enzymes can be used to generate stable, targeted concentrations of peracids for disinfection and/or bleaching applications.
In this disclosure, a number of terms and abbreviations are used. The following definitions apply unless specifically stated otherwise.
As used herein, the term “comprising” means the presence of the stated features, integers, steps, or components as referred to in the claims, but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. The term “comprising” is intended to include embodiments encompassed by the terms “consisting essentially of” and “consisting of”. Similarly, the term “consisting essentially of” is intended to include embodiments encompassed by the term “consisting of”.
As used herein, the term “about” modifying the quantity of an ingredient or reactant employed refers to variation in the numerical quantity that can occur, for example, through typical measuring and liquid handling procedures used for making concentrates or use solutions in the real world; through inadvertent error in these procedures; through differences in the manufacture, source, or purity of the ingredients employed to make the compositions or carry out the methods; and the like. The term “about” also encompasses amounts that differ due to different equilibrium conditions for a composition resulting from a particular initial mixture.
Whether or not modified by the term “about”, the claims include equivalents to the quantities.
As used herein, the term “peracid” is synonymous with peroxyacid, peroxycarboxylic acid, peroxy acid, percarboxylic acid and peroxoic acid.
As used herein, the term “peracetic acid” is abbreviated as “PAA” and is synonymous with peroxyacetic acid, ethaneperoxoic acid and all other synonyms of CAS Registry Number 79-21-0.
As used herein, the term “monoacetin” is synonymous with glycerol monoacetate, glycerin monoacetate, and glyceryl monoacetate.
As used herein, the term “diacetin” is synonymous with glycerol diacetate; glycerin diacetate, glyceryl diacetate, and all other synonyms of CAS Registry Number 25395-31-7.
As used herein, the term “triacetin” is synonymous with glycerin triacetate; glycerol triacetate; glyceryl triacetate, 1,2,3-triacetoxypropane, 1,2,3-propanetriol triacetate and all other synonyms of CAS Registry Number 102-76-1.
As used herein, the term “monobutyrin” is synonymous with glycerol monobutyrate, glycerin monobutyrate, and glyceryl monobutyrate.
As used herein, the term “dibutyrin” is synonymous with glycerol dibutyrate and glyceryl dibutyrate.
As used herein, the term “tributyrin” is synonymous with glycerol tributyrate, 1,2,3-tributyrylglycerol, and all other synonyms of CAS Registry Number 60-01-5.
As used herein, the term “monopropionin” is synonymous with glycerol monopropionate, glycerin monopropionate, and glyceryl monopropionate.
As used herein, the term “dipropionin” is synonymous with glycerol dipropionate and glyceryl dipropionate.
As used herein, the term “tripropionin” is synonymous with glyceryl tripropionate, glycerol tripropionate, 1,2,3-tripropionylglycerol, and all other synonyms of CAS Registry Number 139-45-7.
As used herein, the term “ethyl acetate” is synonymous with acetic ether, acetoxyethane, ethyl ethanoate, acetic acid ethyl ester, ethanoic acid ethyl ester, ethyl acetic ester and all other synonyms of CAS Registry Number 141-78-6.
As used herein, the term “ethyl lactate” is synonymous with lactic acid ethyl ester and all other synonyms of CAS Registry Number 97-64-3.
As used herein, the terms “acetylated sugar” and “acetylated saccharide” refer to mono-, di- and polysaccharides comprising at least one acetyl group. Examples include, but are not limited to, glucose pentaacetate, xylose tetraacetate, acetylated xylan, acetylated xylan fragments, β-D-ribofuranose-1,2,3,5-tetraacetate, tri-O-acetyl-D-galactal, and tri-O-acetyl-glucal.
As used herein, the terms “hydrocarbyl”, “hydrocarbyl group”, and “hydrocarbyl moiety” mean a straight chain, branched or cyclic arrangement of carbon atoms connected by single, double, or triple carbon to carbon bonds and/or by ether linkages, and substituted accordingly with hydrogen atoms. Such hydrocarbyl groups may be aliphatic and/or aromatic. Examples of hydrocarbyl groups include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, cyclopropyl, cyclobutyl, pentyl, cyclopentyl, methylcyclopentyl, hexyl, cyclohexyl, benzyl, and phenyl. In a preferred embodiment, the hydrocarbyl moiety is a straight chain, branched or cyclic arrangement of carbon atoms connected by single carbon to carbon bonds and/or by ether linkages, and substituted accordingly with hydrogen atoms.
As used herein, the terms “monoesters” and “diesters” of 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 2,5-pentanediol, 1,6-pentanediol, 1,2-hexanediol, 2,5-hexanediol, 1,6-hexanediol, refer to said compounds comprising at least one ester group of the formula RC(O)O, wherein R is a C1 to C7 linear hydrocarbyl moiety.
As used herein, the terms “suitable enzymatic reaction mixture”, “components suitable for in situ generation of a peracid”, “suitable reaction components”, “selected set of reaction components”, and “suitable aqueous reaction mixture” refer to the materials and water in which the reactants and enzyme catalyst come into contact. The reaction components are selected such that the pH of the reaction mixture is used to control the production of the desired target concentration of peroxycarboxylic acid by decreasing and/or inactivating the enzyme catalyst's perhydrolysis activity.
As used herein, the term “reaction products” will refer to the mixture of compounds formed within the reaction mixture after combining the selected reaction components. The reaction products are comprised of the enzymatically-generated peroxycarboxylic acid (e.g., peracetic acid) as well as one or more hydrolysis products (enzymatic and/or chemical hydrolysis products), such as the corresponding carboxylic acid (e.g., acetic acid). In one embodiment, combining the selected set of reaction components generates a reaction mixture capable of forming reaction products that reduce the pH of the reaction mixture whereby the perhydrolysis activity of the enzyme catalyst is substantially decreased and/or inactivated within 10 minutes of combining the reaction components, preferably within about 1 minute to about 10 minutes. In one embodiment, the perhydrolysis activity of the enzyme catalyst is reduced at least 80% in 10 minutes or less after combining the reaction components. The reaction products provide a reaction mixture pH suitable to control the amount of enzymatically-generated peroxycarboxylic acid. The initial reaction pH will be dependent on a number of variables, including reaction component concentrations, reaction temperature, the presence or absence of a buffer, the buffer pKa, and the buffer concentration. In one embodiment, the pH of the reaction mixture drops below about 6.0 within 10 minutes of combining the selected set of reaction components. In another embodiment, the reaction products reduce the reaction mixture pH to less than about 6.0 within about 1 minute to about 10 minutes of combining the reaction components.
The components of the suitable aqueous reaction mixture are provided herein and those skilled in the art appreciate the range of component variations suitable for this process. In one embodiment, the suitable enzymatic reaction mixture produces peracid in situ upon combining the reaction components. As such, the reaction components may be provided as a multicomponent system wherein one or more of the reaction components remains separated until use. The design of systems and means for separating and combining multiple active components are known in the art and generally will depend upon the physical form of the individual reaction components. For example, multiple active fluids (liquid-liquid) systems typically use multichamber dispenser bottles or two-phase systems (U.S. Patent Application Pub. No. 2005/0139608; U.S. Pat. No. 5,398,846; U.S. Pat. No. 5,624,634; U.S. Pat. No. 6,391,840; E.P. Patent 0807156B1; U.S. Patent Appln. Pub. No. 2005/0008526; and PCT Publication No. WO 00/11713A1) such as found in some bleaching applications wherein the desired bleaching agent is produced upon mixing the reactive fluids. Other forms of multicomponent systems used to generate peracid may include, but are not limited to those designed for one or more solid components or combinations of solid-liquid components, such as powders (e.g., many commercially available bleaching composition, U.S. Pat. No. 5,116,575), multi-layered tablets (U.S. Pat. No. 6,210,639), water dissolvable packets having multiple compartments (U.S. Pat. No. 6,995,125) and solid agglomerates that react upon the addition of water (U.S. Pat. No. 6,319,888).
One embodiment provides, a process for producing a targeted concentration of peroxycarboxylic acid by controlling the catalytic activity of an enzyme, comprising: combining selected reaction components, under suitable aqueous reaction conditions, to produce a target concentration of peroxycarboxylic acid, said reaction components comprising:
a first mixture comprising:
i) an enzyme catalyst having perhydrolase activity, said enzyme catalyst comprising an enzyme having a CE-7 signature motif; and ii) a carboxylic acid ester substrate, said first mixture optionally comprising a component selected from the group consisting of an inorganic or organic buffer, a corrosion inhibitor, a wetting agent, and combinations thereof; and

a second mixture comprising a source of peroxygen and water, said second mixture optionally comprising a chelating agent.
In a further related embodiment, the carboxylic acid ester substrate in the first mixture of the formulation is selected from the group consisting of:
i) esters having the structure

[X] m R 5 wherein X=an ester group of the formula R 6 —C(O)O R 6 ═C1 to C7 linear, branched or cyclic hydrocarbyl moiety, optionally substituted with hydroxyl groups or C1 to C4 alkoxy groups, wherein R 6 optionally comprises one or more ether linkages for R 6 ═C2 to C7; R 5 =a C1 to C6 linear, branched, or cyclic hydrocarbyl moiety optionally substituted with hydroxyl groups; wherein each carbon atom in R 5 individually comprises no more than one hydroxyl group or no more than one ester group; wherein R 5 optionally comprises one or more ether linkages; m=1 to the number of carbon atoms in R 5 ; and wherein said esters have a solubility in water of at least 5 ppm at 25° C.; ii) glycerides having the structure











wherein R 1 ═C1 to C7 straight chain or branched chain alkyl optionally substituted with an hydroxyl or a C1 to C4 alkoxy group and R 3 and R 4 are individually H or R 1 C(O); and
iii) acetylated saccharides selected from the group consisting of acetylated monosaccharides, acetylated disaccharides, and acetylated polysaccharides;




In another embodiment, the carboxylic acid ester substrate in the first mixture of the formulation is defined by the following formula:









wherein R 1 ═C1 to C7 straight chain or branched chain alkyl optionally substituted with an hydroxyl or a C1 to C4 alkoxy group and R 2 ═C1 to C 10 straight chain or branched chain alkyl, alkenyl, alkynyl, aryl, alkylaryl, alkylheteroaryl, heteroaryl, (CH 2 CH 2 —O) n H or (CH 2 CH(CH 3 )—O) n H and n=1 to 10.
In a preferred embodiment, R 6 is C1 to C7 linear hydrocarbyl moiety, optionally substituted with hydroxyl groups or C1 to C4 alkoxy groups, optionally comprising one or more ether linkages. In a further preferred embodiment, R 6 is C2 to C7 linear hydrocarbyl moiety, optionally substituted with hydroxyl groups, and/or optionally comprising one or more ether linkages.
In another embodiment, the carboxylic acid ester substrate is selected from the group consisting of monoacetin; diacetin; triacetin; monopropionin; dipropionin; tripropionin; monobutyrin; dibutyrin; tributyrin; glucose pentaacetate; xylose tetraacetate; acetylated xylan; acetylated xylan fragments; β-D-ribofuranose-1,2,3,5-tetraacetate; tri-O-acetyl-D-galactal; tri-O-acetyl-glucal; monoesters or diesters of 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 2,5-pentanediol, 1,6-pentanediol, 1,2-hexanediol, 2,5-hexanediol, 1,6-hexanediol; and mixtures thereof.
In another embodiment, the carboxylic acid ester is selected from the group consisting of monoacetin, diacetin, triacetin, and combinations thereof. In another embodiment, the carboxylic acid ester is an acetylated saccharide. In another embodiment, the substrate is a C1 to C6 polyol comprising one or more ester groups. In a preferred embodiment, one or more of the hydroxyl groups on the C1 to C6 polyol are substituted with one or more acetoxy groups (e.g. 1,3-propanediol diacetate, 1,4-butanediol diacetate, etc.). In another embodiment, the enzyme catalyst is a particulate solid. In another embodiment, the first reaction mixture described above is a solid tablet or powder.
As used herein, the term “perhydrolysis” is defined as the reaction of a selected substrate with peroxide to form a peracid. Typically, inorganic peroxide is reacted with the selected substrate in the presence of a catalyst to produce the peracid. Alternatively, hydrogen peroxide can be generated in situ by the reaction of a substrate and oxygen catalyzed by an enzyme having oxidase activity (e.g., glucose oxidase, alcohol oxidase, monoamine oxidase, lactate oxidase, amino acid oxidase). As used herein, the term “chemical perhydrolysis” includes perhydrolysis reactions in which a substrate (a peracid precursor) is combined with a source of hydrogen peroxide wherein peracid is formed in the absence of an enzyme catalyst.
As used herein, the term “perhydrolase activity” refers to the catalyst activity per unit mass (for example, milligram) of protein, dry cell weight, or immobilized catalyst weight.
As used herein, “one unit of enzyme activity” or “one unit of activity” or “U” is defined as the amount of perhydrolase activity required for the production of 1 μmol of peracid product per minute at a specified temperature.
As used herein, the terms “enzyme catalyst” and “perhydrolase catalyst” refer to a catalyst comprising an enzyme having perhydrolysis activity and may be in the form of a whole microbial cell, permeabilized microbial cell(s), one or more cell components of a microbial cell extract, partially purified enzyme, or purified enzyme. The enzyme catalyst may also be chemically modified (e.g., by pegylation or by reaction with cross-linking reagents). The perhydrolase catalyst may also be immobilized on a soluble or insoluble support using methods well-known to those skilled in the art; see for example, Immobilization of Enzymes and Cells ; Gordon F. Bickerstaff, Editor; Humana Press, Totowa, N.J., USA; 1997. As described herein, all of the present enzymes having perhydrolysis activity are structurally members of the carbohydrate family esterase family 7 (CE-7 family) of enzymes (see Coutinho, P. M., Henrissat, B. “Carbohydrate-active enzymes: an integrated database approach” in Recent Advances in Carbohydrate Bioengineering , H. J. Gilbert, G. Davies, B. Henrissat and B. Svensson eds., (1999) The Royal Society of Chemistry, Cambridge, pp. 3-12.).
Members of the CE-7 family include cephalosporin C deacetylases (CAHs; E.C. 3.1.1.41) and acetyl xylan esterases (AXEs; E.C. 11.1.72). Members of the CE-7 esterase family share a conserved signature motif (Vincent et al., J. Mol. Biol., 330:593-606 (2003)). Perhydrolases comprising the CE-7 signature motif and/or a substantially similar structure are suitable for use in the present invention. Means to identify substantially similar biological molecules are well known in the art (e.g. sequence alignment protocols, nucleic acid hybridizations, presence of a conserved signature motif, etc.). In one aspect, the enzyme catalyst in the present process comprises a substantially similar enzyme having at least 30%, preferably at least 33%, more preferably at least 40%, more preferably at least 50%, even more preferably at least 60%, yet even more preferable at least 70%, yet even more preferably at least 80%, yet even more preferably at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity to the sequences provided herein. The nucleic acid molecules encoding the present CE-7 carbohydrate esterases are also provided herein. In a further embodiment, the perhydrolase catalyst useful in the present process is encoded by a nucleic acid molecule that hybridizes stringent conditions to one of the present nucleic acid molecules.
As used herein, the terms “cephalosporin C deacetylase” and “cephalosporin C acetyl hydrolase” refers to an enzyme (E.C. 3.1.1.41) that catalyzes the deacetylation of cephalosporins such as cephalosporin C and 7-aminocephalosporanic acid (Mitsushima et al., Appl. Environ. Microbiol. 61(6): 2224-2229 (1995); U.S. Pat. No. 5,528,152; and U.S. Pat. No. 5,338,676). As described herein, several cephalosporin C deacetylases are provided having significant perhydrolysis activity.
As used herein, “acetyl xylan esterases” refers to an enzyme (E.C. 311.72; AXEs) that catalyzes the deacetylation of acetylated xylans and other acetylated saccharides. As illustrated herein, several enzymes classified as acetyl xylan esterases are provided having significant perhydrolase activity.
As used herein, the term “ Bacillus subtilis (ATCC® 31954™)” refers to a bacterial cell deposited to the American Type Culture Collection (ATCC®) having international depository accession number ATCC® 31954™. Bacillus subtilis ATCC® 31954™ has been reported to have an ester hydrolase (“diacetinase”) activity capable of hydrolyzing glycerol esters having 2-carbon to 8-carbon acyl groups, especially diacetin (U.S. Pat. No. 4,444,886; herein incorporated by reference in its entirety). As described herein, an enzyme having significant perhydrolase activity has been isolated from B. subtilis ATCC® 31954™ and is provided as SEQ ID NO: 2. The amino acid sequence of the isolated enzyme has 100% amino acid identity to the cephalosporin C deacetylase provided by GENBANK® Accession No. BAA01729.1.
As used herein, the term “ Bacillus subtilis BE1010” refers to the strain of Bacillus subtilis as reported by Payne and Jackson ( J. Bacteriol. 173:2278-22.82 (1991)). Bacillus subtilis BE1010 is a derivative Bacillus subtilis subsp. subtilis strain BR151 (ATCC® 33677™) having a chromosomal deletion in the genes encoding subtilisin and neutral protease. As described herein, an enzyme having significant perhydrolase activity has been isolated from B. subtilis BE1010 and is provided as SEQ ID NO: 4. The amino acid sequence of the isolated enzyme has 100% amino acid identity to the cephalosporin C deacetylase reported in Bacillus subtilis subsp. subtilis strain 168 (Kunst et al., Nature, 390:249-256 (1997)).
As used herein, the term “ Bacillus subtilis ATCC® 29233™” refers to a strain of Bacillus subtilis deposited to the American Type Culture Collection (ATCC) having international depository accession number ATCC® 29233™. As described herein, an enzyme having significant perhydrolase activity has been isolated and sequenced from B. subtilis ATCC® 29233 and is provided as SEQ ID NO: 30.
As used herein, the term “ Clostridium thermocellum ATCC® 27405™” refers to a strain of Clostridium thermocellum deposited to the American Type Culture Collection (ATCC®) having international depository accession number ATCC® 27405™. The amino acid sequence of the enzyme having perhydrolase activity from C. thermocellum ATCC® 27405™ is provided as SEQ ID NO: 12.
As used herein, the term “ Bacillus subtilis ATCC® 6633™” refers to a bacterial cell deposited to the American Type Culture Collection (ATCC®) having international depository accession number ATCC® 6633™. Bacillus subtilis ATCC® 6633™ has been reported to have cephalosporin acetylhydrolase activity (U.S. Pat. No. 6,465,233). The amino acid sequence of the enzyme having perhydrolase activity from B. subtilis ATCC® 6633™ is provided as SEQ ID NO: 6.
As used herein, the term “ Bacillus licheniformis ATCC® 14580Th” refers to a bacterial cell deposited to the American Type Culture Collection (ATCC) having international depository accession number ATCC® 14580™. Bacillus licheniformis ATCC® 14580™ has been reported to have cephalosporin acetylhydrolase activity (GENBANK® YP — 077621). The amino acid sequence of the enzyme having perhydrolase activity from B. licheniformis ATCC® 14580™ is provided as SEQ ID NO: 8.
As used herein, the term “ Bacillus pumilus PS213” refers to a bacterial cell reported to have acetyl xylan esterase activity (GENBANK® AJ249957). The amino acid sequence of the enzyme having perhydrolase activity from Bacillus pumilus PS213 is provided as SEQ ID NO: 10.
As used herein, the term “ Thermotoga neapolitana ” refers to a strain of Thermotoga neapolitana reported to have acetyl xylan esterase activity (GENBANK® AAB70869). The amino acid sequence of the enzyme having perhydrolase activity from Thermotoga neapolitana is provided as SEQ ID NO: 14.
As used herein, the term “ Thermotoga maritima MSB8” refers to a bacterial cell reported to have acetyl xylan esterase activity (GENBANK® NP — 227893.1). The amino acid sequence of the enzyme having perhydrolase activity from Thermotoga maritima MSB8 is provided as SEQ ID NO: 16.
As used herein, the term “ Bacillus clausii KSM-K16” refers to a bacterial cell reported to have cephalosporin-C deacetylase activity (GENBANK® YP — 175265). The amino acid sequence of the enzyme having perhydrolase activity from Bacillus clausii KSM-K16 is provided as SEQ ID NO: 24.
As used herein, the term “ Thermoanearobacterium saccharolyticum ” refers to a bacterial strain reported to have acetyl xylan esterase activity (GENBANK® 541858). The amino acid sequence of the enzyme having perhydrolase activity from Thermoanearobacterium saccharolyticum is provided as SEQ ID NO: 54.
As used herein, the term “ Thermotoga lettingae ” refers to a bacterial cell reported to have acetyl xylan esterase activity (GENBANK® CP000812). The deduced amino acid sequence of the enzyme having perhydrolase activity from Thermotoga lettingae is provided as SEQ ID NO: 56.
As used herein, the term “ Thermotoga petrophila ” refers to a bacterial cell reported to have acetyl xylan esterase activity (GENBANK® CP000702). The deduced amino acid sequence of the enzyme having perhydrolase activity from Thermotoga lettingae is provided as SEQ ID NO: 58.
As used herein, the term “ Thermotoga sp. RQ2” refers to a bacterial cell reported to have acetyl xylan esterase activity (GENBANK® CP000969). Two different acetyl xylan esterases have been identified from Thermotoga sp. RQ2 and are referred to herein as “RQ2(a)” (the deduced amino acid sequence provided as SEQ ID NO: 60) and “RQ2(b)” (the deduced amino acid sequence provided as SEQ ID NO: 62).
As used herein, an “isolated nucleic acid molecule” and “isolated nucleic acid fragment” will be used interchangeably and refers to a polymer of RNA or DNA that is single- or double-stranded, optionally containing synthetic, non-natural or altered nucleotide bases. An isolated nucleic acid molecule in the form of a polymer of DNA may be comprised of one or more segments of cDNA, genomic DNA or synthetic DNA.
The term “amino acid” refers to the basic chemical structural unit of a protein or polypeptide. The following abbreviations are used herein to identify specific amino acids:













Three-Letter
One-Letter


Amino Acid
Abbreviation
Abbreviation





Alanine
Ala
A


Arginine
Arg
R


Asparagine
Asn
N


Aspartic acid
Asp
D


Cysteine
Cys
C


Glutamine
Gln
Q


Glutamic acid
Glu
E


Glycine
Gly
G


Histidine
His
H


Isoleucine
Ile
I


Leucine
Leu
L


Lysine
Lys
K


Methionine
Met
M


Phenylalanine
Phe
F


Proline
Pro
P


Serine
Ser
S


Threonine
Thr
T


Tryptophan
Trp
W


Tyrosine
Tyr
Y


Valine
Val
V


Any amino acid
Xaa
X


(or as defined herein)







































As used herein, “substantially similar” refers to nucleic acid molecules wherein changes in one or more nucleotide bases results in the addition, substitution, or deletion of one or more amino acids, but does not affect the functional properties (i.e., perhydrolytic activity) of the protein encoded by the DNA sequence. As used herein, “substantially similar” also refers to an enzyme having an amino acid sequence that is at least 30%, preferably at least 33%, more preferably at least 40%, more preferably at least 50%, even more preferably at least 60%, even more preferably at least 70%, even more preferably at least 80%, yet even more preferably at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identical to the amino acid sequences reported herein wherein the resulting enzyme retains the present functional properties perhydrolytic activity). “Substantially similar” may also refer to an enzyme having perhydrolytic activity encoded by nucleic acid molecules that hybridize under stringent conditions to the nucleic acid molecules reported herein. It is therefore understood that the invention encompasses more than the specific exemplary sequences.
For example, it is well known in the art that alterations in a gene which result in the production of a chemically equivalent amino acid at a given site, but do not affect the functional properties of the encoded protein are common. For the purposes of the present invention substitutions are defined as exchanges within one of the following five groups:
1. Small aliphatic, nonpolar or slightly polar residues: Ala, Ser, Thr (Pro, Gly);
2. Polar, negatively charged residues and their amides: Asp, Asn, Glu, Gln;
3. Polar, positively charged residues: His, Arg, Lys;
4. Large aliphatic, nonpolar residues: Met, Leu, Ile, Val (Cys); and
5. Large aromatic residues: Phe, Tyr, Trp.
Thus, a codon for the amino acid alanine, a hydrophobic amino acid, may be substituted by a codon encoding another less hydrophobic residue (such as glycine) or a more hydrophobic residue (such as valine, leucine, or isoleucine). Similarly, changes which result in substitution of one negatively charged residue for another (such as aspartic acid for glutamic acid) or one positively charged residue for another (such as lysine for arginine) can also be expected to produce a functionally equivalent product. In many cases, nucleotide changes which result in alteration of the N-terminal and C-terminal portions of the protein molecule would also not be expected to alter the activity of the protein.
Each of the proposed modifications is well within the routine skill in the art, as is determination of retention of biological activity of the encoded products. Moreover, the skilled artisan recognizes that substantially similar sequences are encompassed by the present invention. In one embodiment, substantially similar sequences are defined by their ability to hybridize, under stringent conditions (0.1×SSC, 0.1% SDS, 65° C. and washed with 2×SSC, 0.1% SDS followed by 0.1×SSC, 0.1% SDS, 65° C.) with the sequences exemplified herein. In one embodiment, the present invention includes enzymes having perhydrolase activity encoded by isolated nucleic acid molecules that hybridize under stringent conditions to the nucleic acid molecules reported herein. In a preferred embodiment, the present invention includes an enzyme having perhydrolase activity encoded by isolated nucleic acid molecule that hybridizes under stringent conditions to a nucleic acid molecule having a nucleic acid sequence selected from the group consisting of SEQ ID NO: 1, SEQ ID NO: 9, SEQ ID NO: 13, and SEQ ID NO: 15.
As used herein, a nucleic acid molecule is “hybridizable” to another nucleic acid molecule, such as a cDNA, genomic DNA, or RNA, when a single strand of the first molecule can anneal to the other molecule under appropriate conditions of temperature and solution ionic strength. Hybridization and washing conditions are well known and exemplified in Sambrook, J. and Russell, D., T. Molecular Cloning: A Laboratory Manual , Third Edition, Cold Spring Harbor Laboratory Press, Cold Spring Harbor (2001). The conditions of temperature and ionic strength determine the “stringency” of the hybridization. Stringency conditions can be adjusted to screen for moderately similar molecules, such as homologous sequences from distantly related organisms, to highly similar molecules, such as genes that duplicate functional enzymes from closely related organisms. Post-hybridization washes typically determine stringency conditions. One set of preferred conditions uses a series of washes stating with 6×SSC, 0.5% SDS at room temperature for 15 min, then repeated with 2×SSC, 0.5% SDS at 45° C. for 30 min, and then repeated twice with 0.2×SSC, 0.5% SDS at 50° C. for 30 min. A more preferred set of conditions uses higher temperatures in which the washes are identical to those above except for the temperature of the final two 30 min washes in 0.2×SSC, 0.5% SDS was increased to 60° C. Another preferred set of stringent hybridization conditions is 0.1×SSC, 0.1% SDS, 65° C. and washed with 2×SSC, 0.1% SDS followed by a final wash of 0.1×SSC, 0.1% SDS, 65° C. with the sequences exemplified herein.
Hybridization requires that the two nucleic acids contain complementary sequences, although depending on the stringency of the hybridization, mismatches between bases are possible. The appropriate stringency for hybridizing nucleic acids depends on the length of the nucleic acids and the degree of complementation, variables well known in the art. The greater the degree of similarity or homology between two nucleotide sequences, the greater the value of Tm for hybrids of nucleic acids having those sequences. The relative stability (corresponding to higher Tm) of nucleic acid hybridizations decreases in the following order: RNA:RNA, DNA:RNA, DNA:DNA. For hybrids of greater than 100 nucleotides in length, equations for calculating Tm have been derived (Sambrook and Russell, supra). For hybridizations with shorter nucleic acids, i.e., oligonucleotides, the position of mismatches becomes more important, and the length of the oligonucleotide determines its specificity (Sambrook and Russell, supra). In one aspect, the length for a hybridizable nucleic acid is at least about 10 nucleotides. Preferably, a minimum length for a hybridizable nucleic acid is at least about 15 nucleotides in length, more preferably at least about 20 nucleotides in length, even more preferably at least 30 nucleotides in length, even more preferably at least 300 nucleotides in length, and most preferably at least 800 nucleotides in length. Furthermore, the skilled artisan will recognize that the temperature and wash solution salt concentration may be adjusted as necessary according to factors such as length of the probe.
As used herein, the term “percent identity” is a relationship between two or more polypeptide sequences or two or more polynucleotide sequences, as determined by comparing the sequences. In the art, “identity” also means the degree of sequence relatedness between polypeptide or polynucleotide sequences, as the case may be, as determined by the match between strings of such sequences. “Identity” and “similarity” can be readily calculated by known methods, including but not limited to those described in: Computational Molecular Biology (Lesk, A. M., ed.) Oxford University Press, NY (1988); Biocomputing: Informatics and Genome Projects (Smith, D. W., ed.) Academic Press, NY (1993); Computer Analysis of Sequence Data, Part I (Griffin, A. M., and Griffin, H. G., eds.) Humana Press, NJ (1994); Sequence Analysis in Molecular Biology (von Heinje, G., ed.) Academic Press (1987); and Sequence Analysis Primer (Gribskov, M. and Devereux, J., eds.) Stockton Press, NY (1991). Methods to determine identity and similarity are codified in publicly available computer programs. Sequence alignments and percent identity calculations may be performed using the Megalign program of the LASERGENE bioinformatics computing suite (DNASTAR Inc., Madison, Wis.), the AlignX program of Vector NTI v. 7.0 (Informax, Inc., Bethesda, Md.), or the EMBOSS Open Software Suite (EMBL-EBI; Rice et al., Trends in Genetics 16, (6) pp 276-277 (2000)). Multiple alignment of the sequences can be performed using the Clustal method (i.e., CLUSTALW; for example version 1.83) of alignment (Higgins and Sharp, CABIOS, 5:151-153 (1989); Higgins et al., Nucleic Acids Res., 22:4673-4680 (1994); and Chema et al., Nucleic Acids Res., 31 (13):3497-500 (2003)), available from the European Molecular Biology Laboratory via the European Bioinformatics Institute) with the default parameters. Suitable parameters for CLUSTALW protein alignments include GAP Existence penalty=15, GAP extension=0.2, matrix=Gonnet (e.g., Gonnet250), protein ENDGAP=−1, Protein GAPDIST=4, and KTUPLE=1. In one embodiment, a fast or slow alignment is used with the default settings where a slow alignment is preferred. Alternatively, the parameters using the CLUSTALW method (version 1.83) may be modified to also use KTUPLE=1, GAP PENALTY=10, GAP extension=1, matrix=BLOSUM (e.g. BLOSUM64), WINDOW=5, and TOP DIAGONALS SAVED=5.
In one aspect of the present invention, suitable isolated nucleic acid molecules (isolated polynucleotides of the present invention) encode a polypeptide having an amino acid sequence that is at least about 30%, preferably at least 33%, preferably at least 40%, preferably at least 50%, preferably at least 60%, more preferably at least 70%, more preferably at least 80%, even more preferably at least 85%, even more preferably at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identical to the amino acid sequences reported herein. Suitable nucleic acid molecules of the present invention not only have the above homologies, but also typically encode a polypeptide having about 300 to about 340 amino acids, more preferably about 310 to about 330 amino acids, and most preferably about 318 amino acids.
As used herein, the terms “signature motif”, “CE-7 signature motif”, and “diagnostic motif” refer to conserved structures shared among a family of enzymes having a defined activity. The signature motif can be used to define and/or identify the family of structurally related enzymes having similar enzymatic activity for a defined family of substrates. The signature motif can be a single contiguous amino acid sequence or a collection of discontiguous, conserved motifs that together form the signature motif. Typically, the conserved motif(s) is represented by an amino acid sequence. As described herein, the present perhydrolases belong to the family of CE-7 carbohydrate esterases. This family of enzymes can be defined by the presence of a signature motif (Vincent et al., supra).
As used herein, “codon degeneracy” refers to the nature of the genetic code permitting variation of the nucleotide sequence without affecting the amino acid sequence of an encoded polypeptide. Accordingly, the present invention relates to any nucleic acid molecule that encodes all or a substantial portion of the amino acid sequences encoding the present microbial polypeptide. The skilled artisan is well aware of the “codon-bias” exhibited by a specific host cell in usage of nucleotide codons to specify a given amino acid. Therefore, when synthesizing a gene for improved expression in a host cell, it is desirable to design the gene such that its frequency of codon usage approaches the frequency of preferred codon usage of the host cell.
As used herein, “synthetic genes” can be assembled from oligonucleotide building blocks that are chemically synthesized using procedures known to those skilled in the art. These building blocks are ligated and annealed to form gene segments that are then enzymatically assembled to construct the entire gene. “Chemically synthesized”, as pertaining to a DNA sequence, means that the component nucleotides were assembled in vitro. Manual chemical synthesis of DNA may be accomplished using well-established procedures, or automated chemical synthesis can be performed using one of a number of commercially available machines. Accordingly, the genes can be tailored for optimal gene expression based on optimization of nucleotide sequences to reflect the codon bias of the host cell. The skilled artisan appreciates the likelihood of successful gene expression if codon usage is biased towards those codons favored by the host. Determination of preferred codons can be based on a survey of genes derived from the host cell where sequence information is available.
As used herein, “gene” refers to a nucleic acid molecule that expresses a specific protein, including regulatory sequences preceding (5′ non-coding sequences) and following (3′ non-coding sequences) the coding sequence. “Native gene” refers to a gene as found in nature with its own regulatory sequences. “Chimeric gene” refers to any gene that is not a native gene, comprising regulatory and coding sequences that are not found together in nature. Accordingly, a chimeric gene may comprise regulatory sequences and coding sequences that are derived from different sources, or regulatory sequences and coding sequences derived from the same source, but arranged in a manner different from that found in nature. “Endogenous gene” refers to a native gene in its natural location in the genome of an organism. A “foreign” gene refers to a gene not normally found in the host organism, but that is introduced into the host organism by gene transfer. Foreign genes can comprise native genes inserted into a non-native organism, or chimeric genes. A “transgene” is a gene that has been introduced into the genome by a transformation procedure.
As used herein, “coding sequence” refers to a DNA sequence that codes for a specific amino acid sequence. “Suitable regulatory sequences” refer to nucleotide sequences located upstream (5′ non-coding sequences), within, or downstream (3′ non-coding sequences) of a coding sequence, and which influence the transcription, RNA processing or stability, or translation of the associated coding sequence. Regulatory sequences may include promoters, translation leader sequences, RNA processing site, effector binding site and stem-loop structure.
As used herein, “promoter” refers to a DNA sequence capable of controlling the expression of a coding sequence or functional RNA. In general, a coding sequence is located 3′ to a promoter sequence. Promoters may be derived in their entirety from a native gene, or be composed of different elements derived from different promoters found in nature, or even comprise synthetic DNA segments. It is understood by those skilled in the art that different promoters may direct the expression of a gene at different stages of development, or in response to different environmental or physiological conditions. Promoters that cause a gene to be expressed at most times are commonly referred to as “constitutive promoters”. It is further recognized that since in most cases the exact boundaries of regulatory sequences have not been completely defined, DNA fragments of different lengths may have identical promoter activity.
As used herein, the “3′ non-coding sequences” refer to DNA sequences located downstream of a coding sequence and include polyadenylation recognition sequences (normally limited to eukaryotes) and other sequences encoding regulatory signals capable of affecting mRNA processing or gene expression. The polyadenylation signal is usually characterized by affecting the addition of polyadenylic acid tracts (normally limited to eukaryotes) to the 3′ end of the mRNA precursor.
As used herein, the term “operably linked” refers to the association of nucleic acid sequences on a single nucleic acid molecule so that the function of one is affected by the other. For example, a promoter is operably linked with a coding sequence when it is capable of affecting the expression of that coding sequence, i.e., that the coding sequence is under the transcriptional control of the promoter. Coding sequences can be operably linked to regulatory sequences in sense or antisense orientation.
As used herein, the term “expression” refers to the transcription and stable accumulation of sense (mRNA) or antisense RNA derived from the nucleic acid molecule described herein. Expression may also refer to translation of mRNA into a polypeptide.
As used herein, “transformation” refers to the transfer of a nucleic acid molecule into the genome of a host organism, resulting in genetically stable inheritance. In the present invention, the host cell's genome includes chromosomal and extrachromosomal (e.g. plasmid) genes. Host organisms containing the transformed nucleic acid molecules are referred to as “transgenic” or “recombinant” or “transformed” organisms.
As used herein, the terms “plasmid”, “vector” and “cassette” refer to an extrachromosomal element often carrying genes which are not part of the central metabolism of the cell, and usually in the form of circular double-stranded DNA molecules. Such elements may be autonomously replicating sequences, genome integrating sequences, phage or nucleotide sequences, linear or circular, of a single- or double-stranded DNA or RNA, derived from any source, in which a number of nucleotide sequences have been joined or recombined into a unique construction which is capable of introducing a promoter fragment and DNA sequence for a selected gene product along with appropriate 3′ untranslated sequence into a cell. “Transformation cassette” refers to a specific vector containing a foreign gene and having elements in addition to the foreign gene that facilitate transformation of a particular host cell. “Expression cassette” refers to a specific vector containing a foreign gene and having elements in addition to the foreign gene that allow for enhanced expression of that gene in a foreign host.
As used herein, the term “sequence analysis software” refers to any computer algorithm or software program that is useful for the analysis of nucleotide or amino acid sequences. “Sequence analysis software” may be commercially available or independently developed. Typical sequence analysis software will include, but is not limited to, the GCG suite of programs (Wisconsin Package Version 9.0, Genetics Computer Group (GCG), Madison, Wis.), BLASTP, BLASTN, BLASTX (Altschul et al., J. Mol. Biol. 215:403-410 (1990), and DNASTAR (DNASTAR, Inc. 1228 S. Park St. Madison, Wis. 53715 USA), CLUSTALW (for example, version 1.83; Thompson et al., Nucleic Acids Research, 22(22):4673-4680 (1994), and the FASTA program incorporating the Smith-Waterman algorithm (W. R. Pearson, Comput. Methods Genome Res ., [Proc. Int. Symp.] (1994), Meeting Date 1992, 111-20. Editor(s): Suhai, Sandor. Publisher: Plenum, New York, N.Y.), Vector NTI (Informax, Bethesda, Md.) and Sequencher v. 4.05. Within the context of this application it will be understood that where sequence analysis software is used for analysis, that the results of the analysis will be based on the “default values” of the program referenced, unless otherwise specified. As used herein “default values” will mean any set of values or parameters set by the software manufacturer that originally load with the software when first initialized.
As used herein, the term “biological contaminants” refers to one or more unwanted and/or pathogenic biological entities including, but not limited to, microorganisms, spores, viruses, prions, and mixtures thereof. The process produces an efficacious concentration of at least one percarboxylic acid useful to reduce and/or eliminate the presence of the viable biological contaminants. In a preferred embodiment, the microbial contaminant is a viable pathogenic microorganism.
As used herein, the term “disinfect” refers to the process of destruction of or prevention of the growth of biological contaminants. As used herein, the term “disinfectant” refers to an agent that disinfects by destroying, neutralizing, or inhibiting the growth of biological contaminants. Typically, disinfectants are used to treat inanimate objects or surfaces. As used herein, the term “antiseptic” refers to a chemical agent that inhibits the growth of disease-carrying microorganisms. In one aspect of the embodiment, the biological contaminants are pathogenic microorganisms.
As used herein, the term “virucide” refers to an agent that inhibits or destroys viruses, and is synonymous with “viricide”. An agent that exhibits the ability to inhibit or destroy viruses is described as having “virucidal” activity. Peracids can have virucidal activity. Typical alternative virucides known in the art which may be suitable for use with the present invention include, for example, alcohols, ethers, chloroform, formaldehyde, phenols, beta propiolactone, iodine, chlorine, mercury salts, hydroxylamine, ethylene oxide, ethylene glycol, quaternary ammonium compounds, enzymes, and detergents.
As used herein, the term “biocide” refers to a chemical agent, typically broad spectrum, which inactivates or destroys microorganisms. A chemical agent that exhibits the ability to inactivate or destroy microorganisms is described as having “biocidal” activity. Peracids can have biocidal activity. Typical alternative biocides known in the art, which may be suitable for use in the present invention include, for example, chlorine, chlorine dioxide, chloroisocyanurates, hypochlorites, ozone, acrolein, amines, chlorinated phenolics, copper salts, organo-sulphur compounds, and quaternary ammonium salts.
As used herein, the phrase “minimum biocidal concentration” refers to the minimum concentration of a biocidal agent that, for a specific contact time, will produce a desired lethal, irreversible reduction in the viable population of the targeted microorganisms. The effectiveness can be measured by the log 10 reduction in viable microorganisms after treatment. In one aspect, the targeted reduction in viable microorganisms after treatment is at least a 3-log reduction, more preferably at least a 4-log reduction, and most preferably at least a 5-log reduction. In another aspect, the minimum biocidal concentration is at least a 6-log reduction in viable microbial cells.
As used herein, the terms “peroxygen source” and “source of peroxygen” refer to compounds capable of providing hydrogen peroxide at a concentration of about 1 mM or more when in an aqueous solution including, but not limited to, hydrogen peroxide, hydrogen peroxide adducts (e.g., urea-hydrogen peroxide adduct (carbamide peroxide)), perborates, and percarbonates. As described herein, the concentration of the hydrogen peroxide provided by the peroxygen compound in the aqueous reaction mixture is initially at least 1 mM or more upon combining the reaction components. In one embodiment, the hydrogen peroxide concentration in the aqueous reaction mixture is at least 10 mM. In another embodiment, the hydrogen peroxide concentration in the aqueous reaction mixture is at least 100 mM. In another embodiment, the hydrogen peroxide concentration in the aqueous reaction mixture is at least 200 mM. In another embodiment, the hydrogen peroxide concentration in the aqueous reaction mixture is 500 mM or more. In yet another embodiment, the hydrogen peroxide concentration in the aqueous reaction mixture is 1000 mM or more. The molar ratio of the hydrogen peroxide to enzyme substrate, e.g. triglyceride, (H 2 O 2 :substrate) in the aqueous reaction mixture may be from about 0.002 to 20, preferably about 0.1 to 10, and most preferably about 0.5 to 5. Alternatively, a peroxygen source (e.g., hydrogen peroxide) can be generated in situ by the reaction of a substrate and oxygen catalyzed by an enzyme having oxidase activity (e.g., glucose oxidase, alcohol oxidase, monoamine oxidase, lactate oxidase, amino acid oxidase).
Suitable Reaction Conditions for Controlling the Enzyme-Catalyzed Preparation of Peracids from Carboxylic Acid Esters and Hydrogen Peroxide
In one aspect, a process is provided to produce an aqueous mixture comprising a target concentration of peracid by reacting carboxylic acid esters and an inorganic peroxide, not limited to hydrogen peroxide, sodium perborate or sodium percarbonate, in the presence of an enzyme catalyst having pH-sensitive perhydrolysis activity. In one embodiment, the enzyme catalyst comprises a perhydrolase having a structure belonging to the CE-7 carbohydrate esterase family.
In another embodiment, the perhydrolase catalyst is structurally classified as a cephalosporin C deacetylase. In another embodiment, the perhydrolase catalyst is structurally classified as an acetyl xylan esterase.
In one embodiment, the perhydrolase catalyst comprises an enzyme having a CE-7 signature motif that aligns with a reference sequence SEQ ID NO: 2 using CLUSTALW, said signature motif comprising:
i) an RGQ motif at amino acid positions 118-120 of SEQ ID NO:2;
ii) a GXSQG motif at amino acid positions 179-183 of SEQ ID NO:2; and
iii) an HE motif at amino acid positions 298-299 of SEQ ID NO:2;
wherein said enzyme also comprises at least 30% amino acid identity to SEQ ID NO: 2.
In a further embodiment, the signature motif additional comprises a forth conserved motif defined as an LXD motif at amino acid residues 267-269 when aligned to reference sequence SEQ ID NO: 2 using CLUSTALW.
In another embodiment, the perhydrolase catalyst comprises an enzyme having an amino acid sequence selected from the group consisting of SEQ ID NO: 2, SEQ ID NO: 4, SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 10, SEQ ID NO: 12, SEQ ID NO: 14, SEQ ID NO: 16, SEQ ID NO: 18, SEQ ID NO: 20, SEQ ID NO: 22, SEQ ID NO: 24, SEQ ID NO: 30, SEQ ID NO: 54, SEQ ID NO: 56, SEQ ID NO: 58, SEQ ID NO: 60, and SEQ ID NO: 62, or a substantially similar enzyme having perhydrolase activity derived by substituting, deleting or adding one or more amino acids to said amino acid sequence.
In another embodiment, a substantially similar enzyme having an amino acid sequence that is at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identical to one or more amino acid sequences selected from the group consisting of SEQ ID NO: 2, SEQ ID NO: 4, SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 10, SEQ ID NO: 12, SEQ ID NO: 14, SEQ ID NO: 16, SEQ ID NO: 18, SEQ ID NO: 20, SEQ ID NO: 22, SEQ ID NO: 24, SEQ ID NO: 30, SEQ ID NO: 54, SEQ ID NO: 56, SEQ ID NO: 58, SEQ ID NO: 60, and SEQ ID NO: 62.
In another embodiment, the perhydrolase catalyst comprises an enzyme having an amino acid sequence encoded by a nucleic acid molecule that hybridizes to a nucleic acid sequence selected from the group consisting of SEQ ID NO: 1; SEQ ID NO: 3; SEQ ID NO: 5, SEQ ID NO: 7, SEQ ID NO: 9, SEQ ID NO: 11, SEQ ID NO: 13, SEQ ID NO: 15, SEQ ID NO: 17, SEQ ID NO: 19, SEQ ID NO: 21, SEQ ID NO: 23, SEQ ID NO: 29, SEQ ID NO: 55, SEQ ID NO: 57, SEQ ID NO: 59, and SEQ ID NO: 61 under stringent hybridization conditions.
In another embodiment, the perhydrolase catalyst comprises an enzyme having at least 30%, preferably at last 36%, amino acid identity to a contiguous signature motif defined as SEQ ID NO: 61 wherein the conserved motifs described above (e.g. RGQ, GXSQG, and LIE, and optionally, LXD) are conserved.
In one embodiment, suitable substrates include esters provided by the following formula:
[X] m R 5 wherein X=an ester group of the formula R 6 C(O)O R 6 ═C1 to C7 linear, branched or cyclic hydrocarbyl moiety, optionally substituted with hydroxyl groups or C1 to C4 alkoxy groups, wherein R 6 optionally comprises one or more ether linkages for R6=C2 to C7; R 5 =a C1 to C6 linear, branched, or cyclic hydrocarbyl moiety optionally substituted with hydroxyl groups; wherein each carbon atom in R 5 individually comprises no more than one hydroxyl group or no more than one ester group; wherein R 5 optionally comprises one or more ether linkages; m=1 to the number of carbon atoms in R 5 ; and
wherein said esters have a solubility in water of at least 5 ppm at 25° C.

In another embodiment, suitable substrates also include esters of the formula:









wherein R 1 ═C1 to C7 straight chain or branched chain alkyl optionally substituted with an hydroxyl or a C1 to C4 alkoxy group and R 2 ═C 1 to C 10 straight chain or branched chain alkyl, alkenyl, alkynyl, aryl, alkylaryl, alkylheteroaryl, heteroaryl, (CH 2 CH 2 —O) n H or (CH 2 CH(CH 3 )—O) n H and n=1 to 10.
In another embodiment, suitable substrates include glycerides of the formula:









wherein R 1 ═C1 to C7 straight chain or branched chain alkyl optionally substituted with an hydroxyl or a C1 to C4 alkoxy group and R 3 and R 4 are individually H or R 1 C(O).
In another embodiment, R 6 is C1 to C7 linear hydrocarbyl moiety, optionally substituted with hydroxyl groups or C1 to C4 alkoxy groups, optionally comprising one or more ether linkages. In a further preferred embodiment, R 6 is C2 to C7 linear hydrocarbyl moiety, optionally substituted with hydroxyl groups, and/or optionally comprising one or more ether linkages.
In another embodiment, suitable substrates also include acetylated saccharides selected from the group consisting of acetylated mono-, di-, and polysaccharides. In a preferred embodiment, the acetylated saccharides include acetylated mono- , di-, and polysaccharides. In another embodiment, the acetylated saccharides are selected from the group consisting of acetylated xylan, fragments of acetylated xylan, acetylated xylose(such as xylose tetraacetate), acetylated glucose (such as glucose pentaacetate), β-D-ribofuranose-1,2,3,5-tetraacetate, tri-O-acetyl-D-galactal, and tri-O-acetyl-D-glucal, and acetylated cellulose. In a preferred embodiment, the acetylated saccharide is selected from the group consisting of β-D-ribofuranose-1,2,3,5-tetraacetate, tri-O-acetyl-D-galactal, and tri-O-acetyl-D-glucal, and acetylated cellulose . As such, acetylated carbohydrates may be suitable substrates for generating percarboxylic acids using the present process (i.e., in the presence of a peroxygen source).
In one embodiment, the substrate is selected from the group consisting of: monoacetin; diacetin; triacetin; monopropionin; dipropionin; tripropionin; monobutyrin; dibutyrin; tributyrin; glucose pentaacetate; xylose tetraacetate; acetylated xylan; acetylated xylan fragments; β-D-ribofuranose-1,2,3,5-tetraacetate; tri-O-acetyl-D-galactal; tri-O-acetyl-glucal; monoesters or diesters of 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 2,5-pentanediol, 1,6-pentanediol, 1,2-hexanediol, 2,5-hexanediol, 1,6-hexanediol; and mixtures thereof.
In a preferred embodiment, the substrate is selected from the group consisting of ethyl acetate, methyl lactate, ethyl lactate, methyl glycolate, ethyl glycolate, methyl methoxyacetate, ethyl methoxyacetate, methyl 3-hydroxybutyrate, ethyl 3-hydroxybutyrate, triethyl 2-acetyl citrate, glucose pentaacetate, gluconolactone, glycerides (mono-, di-, and triglycerides) such as monoacetin, diacetin, triacetin, monopropionin, dipropionin (glyceryl dipropionate), tripropionin (1,2,3-tripropionylglycerol), monobutyrin, dibutyrin (glyceryl dibutyrate), tributyrin (1,2,3-tributyrylglycerol), acetylated saccharides, and mixtures thereof.
In a further preferred aspect, the carboxylic acid ester substrates are selected from the group consisting of monoacetin, diacetin, triacetin, monopropionin, dipropionin, tripropionin, monobutyrin, dibutyrin, tributyrin, ethyl acetate, and ethyl lactate. In yet another aspect, the carboxylic acid ester substrates are selected from the group consisting of diacetin, triacetin, ethyl acetate, and ethyl lactate. In a preferred aspect, the carboxylic acid ester is a glyceride selected from the group consisting of monoacetin, diacetin, triacetin, and mixtures thereof.
The carboxylic acid ester is present in the reaction mixture at a concentration sufficient to produce the desired concentration of peracid upon enzyme-catalyzed perhydrolysis. The carboxylic acid ester need not be completely soluble in the reaction mixture, but has sufficient solubility to permit conversion of the ester by the perhydrolase catalyst to the corresponding peracid. The carboxylic acid ester is present in the reaction mixture at a concentration of 0.0005 wt % to 40 wt % of the reaction mixture, preferably at a concentration of 0.1 wt % to 20 wt % of the reaction mixture, and more preferably at a concentration of 0.5 wt % to 10 wt % of the reaction mixture. The wt % of carboxylic acid ester may optionally be greater than the solubility limit of the carboxylic acid ester, such that the concentration of the carboxylic acid ester is at least 0.0005 wt % in the reaction mixture that is comprised of water, enzyme catalyst, and source of peroxide, where the remainder of the carboxylic acid ester remains as a second separate phase of a two-phase aqueous/organic reaction mixture. Not all of the added carboxylic acid ester must immediately dissolve in the aqueous reaction mixture, and after an initial mixing of all reaction components, additional continuous or discontinuous mixing is optional.
The peroxygen source may include, but is not limited to, hydrogen peroxide, hydrogen peroxide adducts (e.g., urea-hydrogen peroxide adduct (carbamide peroxide)) perborate salts and percarbonate salts. The concentration of peroxygen compound in the reaction mixture may range from 0.0033 wt % to about 50 wt %, preferably from 0.033 wt % to about 40 wt %, more preferably from 0.33 wt % to about 30 wt %.
Many perhydrolase catalysts (whole cells, permeabilized whole cells, and partially purified whole cell extracts each containing an enzyme having perhydrolase activity) have been reported to also have one or more enzymes having catalase activity (EC 1.11.1.6). Catalases catalyze the conversion of hydrogen peroxide into oxygen and water. In one aspect, the perhydrolysis catalyst lacks catalase activity. In another aspect, a catalase inhibitor is added to the reaction mixture. Examples of catalase inhibitors include, but are not limited to, sodium azide and hydroxylamine sulfate. One of skill in the art can adjust the concentration of catalase inhibitor as needed. The concentration of the catalase inhibitor typically ranges from 0.1 mM to about 1 M; preferably about 1 mM to about 50 mM; more preferably from about 1 mM to about 20 mM. In one aspect, sodium azide concentration typically ranges from about 20 mM to about 60 mM while hydroxylamine sulfate is concentration is typically about 0.5 mM to about 30 mM, preferably about 10 mM.
In another embodiment, the perhydrolase catalyst lacks significant catalase activity or is engineered to decrease or eliminate catalase activity. The catalase activity in a host cell can be down-regulated or eliminated by disrupting expression of the gene(s) responsible for the catalase activity using well known techniques including, but not limited to, transposon mutagenesis, RNA antisense expression, targeted mutagenesis, and random mutagenesis. In a preferred embodiment, the gene(s) encoding the endogenous catalase activity are down-regulated or disrupted (i.e. knocked-out). As used herein, a “disrupted” gene is one where the activity and/or function of the protein encoded by the modified gene is no longer present. Means to disrupt a gene are well-known in the art and may include, but are not limited to insertions, deletions, or mutations to the gene so long as the activity and/or function of the corresponding protein is no longer present. In a further preferred embodiment, the production host is an E. coli production host comprising a disrupted catalase gene selected from the group consisting of katG (SEQ ID NO: 40) and katE (SEQ ID NO: 49). In another embodiment, the production host is an E. coli strain comprising a down-regulation and/or disruption in both katg1 and a katE catalase genes. An E. coli strain comprising a double-knockout of katG and katE is provided herein (see Example 3; E. coli strain KLP18).
The catalase negative E. coli strain KLP18 (katG and katE double knockout) that was constructed (Example 3) was demonstrated to be a superior host for large scale (10-L and greater) production of perhydrolase enzymes compared to the catalase negative strain UM2 ( E. coli Genetic Stock Center #7156, Yale University, New Haven Conn.), as determined by growth under fermenter conditions. Although both KLP18 and UM2 are catalase-negative strains, UM2 is known to have numerous nutritional auxotrophies, and therefore requires media that is enriched with yeast extract and peptone. Even when employing enriched media for fermentation, UM2 grew poorly and to a limited maximum cell density (OD). In contrast, KLP18 had no special nutritional requirements and grew to high cell densities on mineral media alone or with additional yeast extract.
The concentration of the perhydrolase catalyst in the aqueous reaction mixture depends on the specific catalytic activity of the catalyst, and is chosen to obtain the desired rate of reaction. The weight of perhydrolase catalyst in perhydrolysis reactions typically ranges from 0.0001 mg to 10 mg per mL of total reaction volume, preferably from 0.001 mg to 1.0 mg per mL. The catalyst may also be immobilized on a soluble or insoluble support using methods well-known to those skilled in the art; see for example, Immobilization of Enzymes and Cells ; Gordon F. Bickerstaff, Editor; Humana Press, Totowa, N.J., USA; 1997. The use of immobilized catalysts permits the recovery and reuse of the catalyst in subsequent reactions. The enzyme catalyst may be in the form of whole microbial cells, permeabilized microbial cells, microbial cell extracts, partially-purified or purified enzymes, and mixtures thereof.
In one aspect, the concentration of peracid generated by the combination of chemical perhydrolysis and enzymatic perhydrolysis of the carboxylic acid ester is sufficient to provide an effective concentration of peracid for bleaching or disinfection at a desired pH. In another aspect, the present methods provide combinations of enzymes and enzyme substrates to produce the desired effective concentration of peracid, where, in the absence of added enzyme, there is a significantly lower concentration of peracid produced. Although there may in some cases be substantial chemical perhydrolysis of the enzyme substrate by direct chemical reaction of inorganic peroxide with the enzyme substrate, there may not be a sufficient concentration of peracid generated to provide an effective concentration of peracid in the desired applications, and a significant increase in total peracid concentration is achieved by the addition of an appropriate perhydrolase catalyst to the reaction mixture.
Peracids can be corrosive to certain metal surfaces, caustic to users, or otherwise destructive, so it may be desirable to limit the total amount of peracid produced during the reaction to prevent or minimize its corrosive effect. For example, applications that require production of no more than about 100 to about 1000 ppm of peracid in about 1 minute to about 5 minutes often employ reaction conditions that yield a final concentration of peracid well above this limit. In such instances it can be desirable to regulate the amount of peracid produced and, in some cases, to regulate the rate at which the peracid is produced.
As described herein, an aqueous reaction mixture can produce a limited amount of peracid if the proper reaction conditions are used. One component of the reaction mixture that can be important in this regard is a buffer, specifically the pKa and concentration of the buffer. These characteristics of the buffer can regulate the pH of the reaction mixture as peracids are produced, and where byproduct carboxylic acids may also be produced by the enzyme-catalyzed hydrolysis of peracid to carboxylic acid and hydrogen peroxide; therefore, selecting a buffer with the proper characteristics is one way to control, or inactivate, the catalytic activity of a pH-sensitive enzyme catalyst in order to produce a target concentration of peracid. The buffer may be any buffer suitable for carrying out an enzymatic perhydrolysis reaction at the desired pH. In some aspects, the buffer is selected from the group consisting of the sodium salt, the potassium salt or mixed sodium and potassium salts of bicarbonate buffer, citrate buffer, methylphosphonate buffer, pyrophosphate buffer and phosphate buffer. In some aspects, the buffer is bicarbonate buffer or citrate buffer. In some aspects, the aqueous reaction mixture having a specific initial pH includes a buffer.
One way to control the amount of peracid produced by an enzyme-driven reaction is to use reaction conditions that selectively reduce, or inactivate, the catalytic function of the enzyme. Accordingly, the initial pH of the reaction mixture may be adjusted such that the pH of the reaction falls as peracid is produced, ultimately resulting in the reaction mixture having a pH that prevents efficient, or substantial, enzyme activity. In one embodiment, the initial pH of the reaction mixture is about 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 8.1, 8.2, 8.3, 8.4, or about 8.5.
In some aspects, the buffer included in the aqueous reaction mixture can establish the initial pH of the reaction mixture. In some aspects, the buffer produces an aqueous reaction mixture with an initial pH of about 4.0 to about 10.0. In some aspects, the buffer produces an aqueous reaction mixture with an initial pH of about 5.0 to about 9.0. In some aspects, the buffer produces an aqueous reaction mixture with an initial pH of about 6.0 to about 8.5. In some aspects, the buffer produces an aqueous reaction mixture with an initial pH of about 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 8.1, 8.2, 8.3, 8.4, or about 8.5. In some aspects, the reaction mixture containing a buffer has an initial pH of about 8.1. In some aspects, the buffer in a reaction mixture having an initial pH of about 8.1 is bicarbonate buffer. In some aspects, the reaction mixture containing a buffer has an initial pH of about 7.2. In some aspects, the buffer in a reaction mixture having an initial pH of about 7.2 is citrate buffer. In some aspects, the buffer in a reaction mixture having an initial pH of about 7.2 is bicarbonate buffer. In some aspects, the buffer in a reaction mixture having an initial pH of about 7.2 is phosphate buffer. In some aspects, the reaction mixture containing a buffer has an initial pH of about 6.5. In some aspects, the buffer in a reaction mixture having an initial pH of about 6.5 is citrate buffer. In some aspects, the buffer in a reaction mixture having an initial pH of about 6.5 is bicarbonate buffer. In some aspects, the buffer in a reaction mixture having an initial pH of about 6.5 is phosphate buffer. In some aspects, the reaction mixture containing a buffer has an initial pH of about 6.0. In some aspects, the buffer in a reaction mixture having an initial pH of about 6.0 is citrate buffer. In some aspects, the buffer in a reaction mixture having an initial pH of about 6.0 is bicarbonate buffer. In some aspects, the buffer in a reaction mixture having an initial pH of about 6.0 is phosphate buffer. In some aspects, the reaction mixture containing a buffer has an initial pH of about 5.5. In some aspects, the buffer in a reaction mixture having an initial pH of about 5.5 is citrate buffer. In some aspects, the buffer in a reaction mixture having an initial pH of about 5.5 is bicarbonate buffer.
As described herein, an aqueous reaction mixture can produce a limited amount of peracid if the proper reaction conditions are used. One aspect of the reaction mixture that can be important in this regard is buffer concentration. For example, a dilute buffer has limited capacity to buffer the reaction mixture as peracid is produced, thereby reducing the pH of the reaction mixture and reducing, or inactivating, enzyme activity. The concentration of the buffer can regulate the pH of the reaction mixture as peracids are produced; therefore, selecting a buffer with the proper concentration is one way to control, or inactivate, the catalytic activity of a pH-sensitive enzyme catalyst to produce a target concentration of peracid. Accordingly, in some aspects, the aqueous reaction mixture includes a buffer having a specific concentration. The buffer may be any buffer suitable for carrying out an enzymatic perhydrolysis reaction. In some aspects, the buffer is selected from the group consisting of, but not limited to, the sodium salt, potassium salt, or mixture of sodium and potassium salts of bicarbonate buffer, citrate buffer, acetate buffer, phosphate buffer, pyrophosphate buffer and methylphosphonate buffer. In some aspects, the buffer is sodium bicarbonate buffer or sodium citrate buffer. In some aspects, the buffer has a concentration of about 0.01 mM to about 200 mM. In some aspects, the buffer has a concentration of about 0.01 mM to about 100 mM. In some aspects, the buffer has a concentration of about 0.01 mM to about 50 mM. In some aspects, the buffer has a concentration of about 100, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, 5 2.5, 1, 0.5, or about 0.1 mM. In some aspects, the buffer has a concentration of about 50 mM. In some aspects, the buffer having an initial concentration of about 50 mM is citrate buffer. In some aspects, the buffer having an initial concentration of about 50 mM is bicarbonate buffer. In some aspects, the buffer has a concentration of about 25 mM to about 1 mM. In some aspects, the buffer having an initial concentration of about 25 mM to about 1 mM is citrate buffer. In some aspects, the buffer having an initial concentration of about 25 mM to about 1 mM is bicarbonate buffer.
The amount of peracid produced by an enzyme-driven reaction can also be regulated by selecting a reaction mixture initial pH and a buffer with a pKa that will cause the pH of the reaction mixture to fall such that the enzymatic activity of the reaction is reduced or inactivated once the desired concentration of peracid is produced. In one aspect, the initial pH of the reaction mixture is about 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 8.1, 8.2, 8.3, 8.4, or about 8.5 and the pKa of the buffer is about 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0 or about 8.1.
In another embodiment, an enzyme catalyst sensitive to acidic pH, where the enzyme activity decreases significantly with decreasing pH, could be used to control an enzyme-catalyzed reaction because the production of peracid would cause the pH of the reaction mixture to fall to a point at which catalytic activity would be reduced significantly or inactivated. In reactions where the enzyme activity may also catalyze the hydrolysis of peracid to carboxylic acid and hydrogen peroxide, the production of carboxylic acid may also cause the pH of the reaction mixture to fall to a point at which catalytic activity would be reduced significantly or inactivated. For example, in one embodiment, total protein extract from B. subtilis ATCC® 31954™ could be used as a catalyst. In another embodiment, a particular enzyme from B. subtilis ATCC® 31954™ having perhydrolase activity could be used as a catalyst. In one embodiment, total protein extract from B. pumilus could be used as a catalyst. In another embodiment, a particular enzyme from B. pumilus having perhydrolase activity could be used as a catalyst. In one embodiment, total protein extract from T. neapolitana could be used as a catalyst. In another embodiment, a particular protein from T. neapolitana having perhydrolase activity could be used as a catalyst. In one embodiment, total protein extract from T. maritima could be used as a catalyst. In another embodiment, a particular protein from T. maritima having perhydrolase activity could be used as a catalyst.
The production of peracid in an aqueous reaction mixture can alter the enzymatic activity of an enzyme catalyzing the production of peracid. For example, production of peracid can lower the pH of the reaction mixture, which can reduce or inactivate the activity of an enzyme catalyst. In reactions where the enzyme activity may also catalyze the hydrolysis of peracid to carboxylic acid and hydrogen peroxide, the production of carboxylic acid may also cause the pH of the reaction mixture to fall to a point at which catalytic activity would be reduced significantly or inactivated. Accordingly, in some aspects, the production of peracid or peracid and carboxylic acid reduces the activity of an enzyme catalyst by about 25% to about 100%. In some aspects, the production of peracid or peracid and carboxylic acid reduces the activity of an enzyme catalyst by about 40% to about 90%. In some aspects, the production of peracid or peracid and carboxylic acid reduces the activity of an enzyme catalyst by about 60% to about 80%. In some aspects, the production of peracid or peracid and carboxylic acid reduces the activity of an enzyme catalyst by about 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or about 100%. In some aspects, the production of peracid or peracid and carboxylic acid reduces the pH of the reaction mixture such that the activity of the enzyme catalyst is reduced by at least about 75%. In some aspects, the production of peracid or peracid and carboxylic acid reduces the pH of the reaction mixture such that the activity of the enzyme catalyst is reduced by at least about 85%. The pH of the final reaction mixture containing peracid is from about 2 to about 9. In some embodiments the pH of the final reaction mixture containing peracid is from about 3 to about 8, more preferably from about 4 to about 7. In some embodiments the pH of the final reaction mixture containing peracid is from about 5 to about 6. In some embodiments the pH of the final reaction mixture containing peracid is from about 5 to about 5.5. In some embodiments the pH of the final reaction mixture containing peracid is from about 4.5 to about 5.
The concentration of peracid generated (e.g. peracetic acid) by the perhydrolysis of at least one carboxylic acid ester is at least about 2 ppm, preferably at least 20 ppm, more preferably at least 100 ppm, more preferably at least 200 ppm, more preferably at least 300 ppm, more preferably at least 500 ppm, more preferably at least 800 ppm, more preferably at least about 1000 ppm within 10 minutes, preferably within 5 minutes, and most preferably within 1 minute of initiating the perhydrolysis reaction. In some aspects, the concentration of peracid generated (e.g. peracetic acid) by the perhydrolysis of at least one carboxylic acid ester is from about 100 ppm to about 1200 ppm, but is not more that about 2500 ppm, within 10 minutes, preferably within 5 minutes, and most preferably within 1 minute of initiating the perhydrolysis reaction. More preferably, the concentration of peracid generated by the perhydrolysis of at least one carboxylic acid ester is from about 400 ppm to about 600 ppm, within 10 minutes, preferably within 5 minutes, and most preferably within 1 minute of initiating the perhydrolysis reaction. The product mixture comprising the peracid may be optionally diluted with water, or a solution predominantly comprised of water, to produce a mixture with the desired lower concentration of peracid. In one aspect, the reaction time required to produce the desired concentration of peracid is not greater than about two hours, preferably not greater than about 30 minutes, more preferably not greater than about 10 minutes, even more preferably not greater than about 5 minutes, and most preferably in about 1 minute or less. In other aspects, a hard surface or inanimate object contaminated with a concentration of a microbial population is contacted with the peracid formed in accordance with the processes described herein within about 1 minute to about 168 hours of combining said reaction components, or within about 1 minute to about 48 hours, or within about 1 minute to 2 hours of combining said reaction components, or any such time interval therein.
In an application for in situ generation of peracetic acid for disinfection of hard surfaces, it can be desirable to rapidly generate a sufficient amount of peracid to disinfect a hard surface, without significantly exceeding the upper efficacious concentration, thereby limiting or preventing the corrosion of the surface. Peracids can be produced in this manner using enzyme-catalyzed reactions having the appropriate buffer, pH, and enzyme concentrations and using an enzyme that is significantly reduced in activity or inactivated by a decrease in pH. Accordingly, in one aspect, the enzyme-catalyzed reaction mixture incorporates a catalytic enzyme that loses activity after producing from about 500 ppm to about 600 ppm of peracid, due to the acidic pH of the reaction mixture once the desired amount of peracid is produced. This sort of reaction mixture can be modified in other embodiments to cause the catalytic enzyme to lose activity after the production of from about 100 ppm to about 200 ppm of peracid, from about 200 ppm to about 300 ppm of peracid, from about 300 ppm to about 400 ppm of peracid, from about 400 ppm to about 500 ppm of peracid, from about 600 ppm to about 700 ppm of peracid, from about 700 to about 800 ppm of peracid, from about 800 ppm to about 900 ppm of peracid, from about 900 ppm to about 1000 ppm of peracid, or from about 100 ppm to about 500 ppm of peracid, from about 500 ppm to about 1000 ppm of peracid, or from about 1000 ppm to about 2000 ppm of peracid, as needed based on the particular application.
In some aspects, it is also important to produce peracids in a short period of time; however, many of these applications also require production of only a fixed amount of peracid. For example, it can be desirable for a mixture giving rise to a peracid-based disinfectant solution to produce only from about 100 ppm to about 1200 ppm of peracid in about 1 minute, such that substantial amounts of peracid are not produced following the first minute of production. Accordingly, provided herein are enzyme-catalyzed reactions for producing peracids in concentrations from about 100 ppm to about 1200 ppm are produced in about 1 minute without significant production of peracids thereafter.
Of course, those of skill in the art will recognize that other reaction conditions relating to pH, pKa, buffer concentration, and catalyst activity/pH sensitivity will provide the means to limit peracid production by the methods described herein. Such conditions and uses thereof are within the scope of this disclosure.
Described are aqueous peracid solutions that maintain a relatively stable concentration of peracid, i.e. within about 20% of a target peracid concentration, after the reduction, or inactivation, of the enzyme-catalyzed production of peracid, and methods for generating such stable peracid solutions. In one embodiment, the stability of the aqueous reaction product comprising the target concentration of peracid concentration is measured in a closed system (for example, a reaction chamber or a container made of a material that does not substantially react with (or enhance degradation of) the peroxycarboxylic acid produced) at room temperature (approximately 21-22° C.). In some preferred embodiments, the aqueous peracid solutions maintain a peracid concentration within about 15%, and more preferably within about 10%, of a target peracid concentration, after the reduction, or inactivation, of the enzyme-catalyzed production of peracid. The stability of the peracid concentration can persist for hours after the reduction, or inactivation, of the enzyme-catalyzed production of peracid. In one embodiment, the peracid concentration is stable for about 3 hours after the enzyme-catalyzed production of peracid is over. In another embodiment, the peracid concentration is stable for about 6 hours after the enzyme-catalyzed production of peracid is over. In one embodiment, the peracid concentration is stable for about 9 hours after the enzyme-catalyzed production of peracid is over. In one embodiment, the peracid concentration is stable for about 12 hours after the enzyme-catalyzed production of peracid is over. In another embodiment, the peracid concentration is stable for about 15 hours after the enzyme-catalyzed production of peracid is over. In another embodiment, the peracid concentration is stable for about 18 hours after the enzyme-catalyzed production of peracid is over. In one embodiment, the peracid concentration is stable for about 21 hours after the enzyme-catalyzed production of peracid is over. In another embodiment, the peracid concentration is stable for about 24 hours after the enzyme-catalyzed production of peracid is over. In one embodiment, the peracid concentration is stable for about 30 hours after the enzyme-catalyzed production of peracid is over. In one embodiment, the peracid concentration is stable for about 36 hours after the enzyme-catalyzed production of peracid is over. In one embodiment, the peracid concentration is stable for about 42 hours after the enzyme-catalyzed production of peracid is over. In another embodiment, the peracid concentration is stable for about 48 hours after the enzyme-catalyzed production of peracid is over. In one embodiment, the peracid concentration is stable for greater than 48 hours after the enzyme-catalyzed production of peracid is over.
The temperature of the reaction is chosen to control both the reaction rate and the stability of the enzyme catalyst activity. The temperature of the reaction may range from just above the freezing point of the reaction mixture (approximately 0° C.) to about 75° C., with a preferred range of reaction temperature of from about 5° C. to about 55° C.
In another aspect, the enzymatic perhydrolysis reaction mixture may contain an organic solvent that acts as a dispersant to enhance the rate of dissolution of the carboxylic acid ester in the reaction mixture. Such solvents include, but are not limited to, propylene glycol methyl ether, acetone, cyclohexanone, diethylene glycol butyl ether, tripropylene glycol methyl ether, diethylene glycol methyl ether, propylene glycol butyl ether, dipropylene glycol methyl ether, cyclohexanol, benzyl alcohol, isopropanol, ethanol, propylene glycol, and mixtures thereof.
In another aspect, the enzymatic perhydrolysis product may contain additional components that provide desirable functionality. These additional components include, but are not limited to buffers, detergent builders, thickening agents, emulsifiers, surfactants, wetting agents, corrosion inhibitors (e.g., benzotriazole), enzyme stabilizers, and peroxide stabilizers (e.g., metal ion chelating agents). Many of the additional components are well known in the detergent industry (see, for example, U.S. Pat. No. 5,932,532; hereby incorporated by reference). Examples of emulsifiers include, but are not limited to polyvinyl alcohol or polyvinylpyrrolidone. Examples of thickening agents include, but are not limited to LAPONITE® RD , corn starch, PVP, CARBOWAX®, CARBOPOL®, CABOSIL®, polysorbate 20, PVA, and lecithin. Examples of buffering systems include, but are not limited to sodium phosphate monobasic/sodium phosphate dibasic; sulfamic acid/triethanolamine; citric acid/triethanolamine; tartaric acid/triethanolamine; succinic acid/triethanolamine; and acetic acid/triethanolamine. Examples of surfactants include, but are not limited to a) non-ionic surfactants such as block copolymers of ethylene oxide or propylene oxide, ethoxylated or propoxylated linear and branched primary and secondary alcohols, and aliphatic phosphine oxides b) cationic surfactants such as quaternary ammonium compounds, particularly quaternary ammonium compounds having a C8-C20 alkyl group bound to a nitrogen atom additionally bound to three C1-C2 alkyl groups, c) anionic surfactants such as alkane carboxylic acids (e.g., C8-C20 fatty acids), alkyl phosphonates, alkane sulfonates (e.g., sodium dodecylsulphate “SDS”) or linear or branched alkyl benzene sulfonates, alkene sulfonates and d) amphoteric and zwitterionic surfactants such as aminocarboxylic acids, aminodicarboxylic acids, alkybetaines, and mixtures thereof. Additional components may include fragrances, dyes, stabilizers of hydrogen peroxide (e.g., metal chelators such as 1-hydroxyethylidene-1,1-diphosphonic acid (DEQUEST® 2010, Solutia Inc., St. Louis, Mo. and ethylenediaminetetraacetic acid (EDTA)), TURPINAL® SL, DEQUEST® 0520, DEQUEST® 0531, stabilizers of enzyme activity (e.g., polyethyleneglycol (PEG)), and detergent builders.
In another aspect, the enzymatic perhydrolysis product may be pre-mixed to generate the desired concentration of peroxycarboxylic acid prior to contacting the surface or inanimate object to be disinfected.
In another aspect, the enzymatic perhydrolysis product is not pre-mixed to generate the desired concentration of peroxycarboxylic acid prior to contacting the surface or inanimate object to be disinfected, but instead, the components of the reaction mixture that generate the desired concentration of percarboxylic acid are contacted with the surface or inanimate object to be disinfected, generating the desired concentration of peroxycarboxylic acid. In some embodiments, the components of the reaction mixture combine or mix at the locus. In some embodiments, the reaction components are delivered or applied to the locus and subsequently mix or combine to generate the desired concentration of peroxycarboxylic acid.
In Situ Production of Peracids Using a Perhydrolase Catalyst
Cephalosporin C deacetylases (E.C. 3.1.1.41; systematic name cephalosporin C acetylhydrolases; CAHs) are enzymes having the ability to hydrolyze the acetyl ester bond on cephalosporins such as cephalosporin C, 7-aminocephalosporanic acid, and 7-(thiophene-2-acetamido)cephalosporanic acid (Abbott, B. and Fukuda, D., Appl. Microbiol. 30(3):413-419 (1975)). CAHs belong to a larger family of structurally related enzymes referred to as the carbohydrate esterase family seven (CE-7; see Coutinho, P. M., Henrissat, B. “Carbohydrate-active enzymes: an integrated database approach” in Recent Advances in Carbohydrate Bioengineering , H. J. Gilbert, G. Davies, B. Henrissat and B. Svensson eds., (1999) The Royal Society of Chemistry, Cambridge, pp. 3-12.)
The CE-7 family includes both CAHs and acetyl xylan esterases (AXEs; E.C. 3.1.1.72). CE-7 family members share a common structural motif and are quite unusual in that they typically exhibit ester hydrolysis activity for both acetylated xylooligosaccharides and cephalosporin C, suggesting that the CE-7 family represents a single class of proteins with a multifunctional deacetylase activity against a range of small substrates (Vincent et al., J. Mol. Biol., 330:593-606 (2003)). Vincent et al. describes the structural similarity among the members of this family and defines a signature sequence motif characteristic of the CE-7 family.
Members of the CE-7 family are found in plants, fungi (e.g., Cephalosporidium acremonium ), yeasts (e.g., Rhodosporidium toruloides, Rhodotorula glutinis ), and bacteria such as Thermoanaerobacterium sp.; Norcardia lactamdurans , and various members of the genus Bacillus (Politino et al., Appl. Environ. Microbiol., 63(12):4807-4811 (1997); Sakai et al., J. Ferment. Bioeng. 85:53-57 (1998); Lorenz, W. and Wiegel, J., J. Bacteriol 179:5436-5441 (1997); Cardoza et al., Appl. Microbiol. Biotechnol., 54(3):406-412 (2000); Mitsushima et al., supra (1995), Abbott, B. and Fukuda, D., Appl. Microbiol. 30(3):413-419 (1975); Vincent et al., supra, Takami et al., NAR, 28(21):4317-4331 (2000); Rey et al., Genome Biol., 5(10): article 77 (2004); Degrassi et al., Microbiology., 146:1585-1591 (2000); U.S. Pat. No. 6,645,233. U.S. Pat. No. 5,281,525; U.S. Pat. No. 5,338,676; and WO 99/03984. A non-comprehensive list of CE-7 carbohydrate esterase family members having significant homology to SEQ ID NO: 2 are provided in Table 1.





TABLE 1



Example of CE-7 Enzymes Having Significant Homology to SEQ ID NO: 2.







Source Organism





(GENBANK ®
Nucleotide
Amino Acid
% Amino Acid

Accession No. of
Sequence
Sequence
Identity to

the CE-7 enzyme)
(SEQ ID NO:)
(SEQ ID NO:)
SEQ ID NO: 2.
Reference










B. subtilis

1
2
100

B. subtilis


ATCC ® 31954 ™



SHS 0133





Mitsushima et al.





supra (1995)

B. subtilis subsp.
3
4
98
Kunst et al.,

subtilis str. 168



supra.

(NP_388200)



WO99/03984

B. subtilis BE1010



Payne and





Jackson, J.






Bacteriol.






173: 2278-2282





(1991))


B. subtilis

5
6
96
U.S. Pat. No. 6,465,233

ATCC ® 6633 ™

(YP_077621.1)


B. subtilis

29
30
96
Abbott and

ATCC ® 29233 ™



Fukuda, supra


B. licheniformis

7
8
77
Rey et al., supra

ATCC ® 14580 ™

(YP_077621.1)

B. pumilus PS213
9
10
76
Degrassi et al.,

(CAB76451.2)



supra


Clostridium

11
12
57
Copeland et al.


thermocellum




US Dept. of

ATCC ® 27405 ™



Energy Joint

(ZP_00504991)



Genome Institute





(JGI-PGF)





Direct





Submission





GENBANK ®





ZP_00504991


Thermotoga

13
14
42
See


neapolitana




GENBANK ®

(AAB70869.1)



AAB70869.1


Thermotoga

15
16
42
Nelson et al.,

maritima MSB8



Nature 399

(NP_227893.1)



(6734): 323-329





(1999)

Bacillus sp.
19
20
40
Siefert et al.

NRRL B-14911



J. Craig Venter

(ZP_01168674)



Institute.





Direct





Submission





Under





GENBANK ®





ZP_01168674


Thermoanaerobacterium

17
18
37
Lorenz and

sp. (AAB68821.1)



Wiegel, supra


Bacillus halodurans

21
22
36
Takami et al.,

C-125



supra

(NP_244192)


Thermoanearobacterium

—
54
35
Lee,


saccharolyticum




Y. E. and Zeikus,

(S41858)



J. G., J Gen






Microbiol.






(1993), 139 Pt





6: 1235-1243


Bacillus clausii

23
24
33
Kobayashi et al.,

KSM-K16




Appl. Microbiol.


(YP_175265)



Biotechnol. 43





(3), 473-481





(1995)


Thermotoga

55
57
37
Copeland et al.


lettingae




US Dept. of

(CP000812)



Energy Joint





Genome Institute





Direct





Submission





GENBANK ®





CP000812


Thermotoga

57
58
41
Copeland et al.


Petrophila




US Dept. of

(CP000702)



Energy Joint





Genome Institute





Direct





Submission





GENBANK ®





CP000702

Thermotoga sp.
59
60
42
Copeland et al.

RQ2



US Dept. of

RQ2(a)



Energy Joint

(CP000969)



Genome Institute





Direct





Submission





GENBANK ®





CP000969

Thermotoga sp.
61
63
42
Copeland et al.

RQ2



US Dept. of

RQ2(b)



Energy Joint

(CP000969)



Genome Institute





Direct





Submission





GENBANK ®





CP000969
























































































































The present perhydrolases are all members of the CE-7 carbohydrate esterase family. As described by Vincent et al. (supra), members of the family share a common signature motif that is characteristic of this family. A CLUSTALW alignment of the present perhydrolases indicates that all of the members belong to the CE-7 carbohydrate esterase family. A comparison of the overall percent amino acid identity amount the present perhydrolases is provided in Table 2.





TABLE 2



Percent Amino Acid Identity Between Perhydrolases 1



















1
2
3
4
5
6
7
8
9
10
11
12
13
14
15





















1
100















2
99
100

3
99
99
100

4
96
96
97
100

5
77
76
77
76
100

6
76
76
76
76
68
100

7
57
57
57
56
56
56
100

8
42
43
43
43
43
42
41
100

9
42
43
42
43
43
42
42
72
100

10
42
43
43
43
44
42
43
71
91
100

11
41
43
43
43
45
42
43
71
97
91
100

12
41
42
42
42
43
41
42
71
98
91
97
100

13
37
37
37
36
39
38
38
64
65
67
66
65
100

14
34
36
35
36
35
36
33
36
32
34
34
33
36
100

15
33
34
33
33
32
34
32
30
30
32
31
31
32
34
100



1 = Percent identity determined using blast2seq algorithm using BLOSUM62, gap open = 11, gap extension = 1, x_drop = 0, expect = 10, and wordsize = 3. Tatiana A. Tatusova, Thomas L. Madden (1999), “Blast 2 sequences - a new tool for comparing protein and nucleotide sequences”, FEMS Microbiol Lett. 174: 247-250

1. B. subtilis ATCC ® 31954 ™

2. B. subtilis BE1010

3. B. subtilis ATCC ® 29233 ™

4. B. subtilis ATCC ® 6633 ™

5. B. licheniformis 14580

6. B. pumilus PS213

7. C. thermocellum ATCC ® 27405 ™

8. Thermotoga sp. RQ2(b)

9. Thermotoga sp. RQ2(a)

10. T. neapolitana

11. T. maritima

12. T. petrophila

13. T. lettingae

14. T. saccharolyticum

15. B. clausii




















































Although variation is observed in terms of overall percent amino acid identity (i.e. the Clostridium thermocellum ATCC® 27405™ perhydrolase; SEQ ID NO: 12 shares only 57% amino acid identity with the Bacillus subtilis ATCC® 31954™ perhydrolase; SEQ ID NO: 2, while the Bacillus clausii perhydrolase (SEQ ID NO: 24) shares only 33% identity with SEQ ID NO: 2), each of the present perhydrolase enzymes share the CE-7 signature motif. Accordingly, the perhydrolase catalyst of the present invention is an enzyme structurally classified as belonging to the CE-7 carbohydrate esterase family. Each of the present perhydrolase enzymes comprises the CE-7 signature (diagnostic) motif.
Vincent et al. (supra) analyzed the structure CE-7 esterases and identified several highly conserved motifs that are diagnostic for the family. These highly conserved motifs include the Arg118-Gly119-Gln120 (RGQ), Gly179-Xaa180-Ser181-Gln182-Gly183 (GXSQG), and His298-Glu299 (HE). In addition, there is a highly conserved Lys267-Xaa268-Asp269 (LXD) motif that may be used to further characterize the signature motif. All sequence numbering is relative to the numbering of a reference sequence ( B. subtilis ATCC® 31954™ perhydrolase; SEQ ID NO: 2).
In one embodiment, suitable perhydrolytic enzymes can be identified by the presence of the CE-7 signature motif (Vincent et al., supra). In a preferred embodiment, perhydrolases comprising the CE-7 signature motif are identified using a CLUSTALW alignment against the Bacillus subtilis ATCC® 31954™ perhydrolase (SEQ ID NO: 2; i.e. the reference sequence used for relative amino acid position numbering). As per the amino acid residue numbering of SEQ ID NO: 2, the CE-7 signature motif comprises 3 conserved motifs defined as:
a) Arg118-Gly119-Gln120;
b) Gly179-Xaa180-Ser181-Gln182-Gly183; and
c) His298-Glu299.
Typically, the Xaa at amino acid residue position 180 is glycine, alanine, proline, tryptophan, or threonine. Two of the three amino acid residues belonging to the catalytic triad are in bold. In one embodiment, the Xaa at amino acid residue position 180 is selected from the group consisting of glycine, alanine, proline, tryptophan, and threonine.
Further analysis of the conserved motifs within the CE-7 carbohydrate esterase family indicates the presence of an additional conserved motif (LXD at amino acid positions 267-269 of SEQ ID NO: 2) that may be to further define a perhydrolase belonging to the CE-7 carbohydrate esterase family (FIGS. 1 a - c ). In a further embodiment, the signature motif defined above includes a forth conserved motif defined as:
Leu267-Xaa268-Asp269.
The Xaa at amino acid residue position 268 is typically isoleucine, valine, or methionine. The forth motif includes the aspartic acid residue (bold) that is the third member of the catalytic triad (Ser181-Asp269-His298).
Any number of well-known global alignment algorithms (i.e. sequence analysis software) may be used to align two or more amino acid sequences (representing enzymes having perhydrolase activity) to determine the existence of the present signature motif (for example, CLUSTALW or Needleman and Wunsch ( J. Mol. Biol., 48:443-453 (1970)). The aligned sequence(s) is compared to the reference sequence (SEQ ID NO: 2). In one embodiment, a CLUSTAL alignment (CLUSTALW) using a reference amino acid sequence (as used herein the CAH sequence (SEQ ID NO: 2) from the Bacillus subtilis ATCC® 31954™) is used to identify perhydrolases belonging to the CE-7 esterase family. The relative numbering of the conserved amino acid residues is based on the residue numbering of the reference amino acid sequence to account for small insertions or deletions (5 amino acids or less) within the aligned sequence.
A comparison of the overall percent identity among perhydrolases exemplified herein indicates that enzymes having as little as 33% identity to SEQ ID NO: 2 (while retaining the signature motif) exhibit significant perhydrolase activity and are structurally classified as CE-7 carbohydrate esterases. In one embodiment, the present perhydrolases include enzymes comprising the present signature motif and at least 30%, preferably at least 33%, more preferably at least 40%, even more preferably at least 42%, even more preferably at least 50%, even more preferably at least 60%, even more preferably at least 70%, even more preferably at least 80%, even more preferably at least 90%, and most preferably at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity to SEQ ID NO: 2.
All of the present perhydrolases are comprised of the above signature motif as shown in Table 3.





TABLE 3



Conserved motifs found within the present

enzymes having perhydrolase activity.








RGQ
GXSQG
LXD
HE


motif a
motif a
motif b
motif a

Perhydrolase
(Residue
(Residue
Residue
(Residue

Sequence
#s)
#s)
#s)
#s)



SEQ ID NO: 2
118-120
179-183
267-269
298-299

SEQ ID NO: 4
118-120
179-183
267-269
298-299

SEQ ID NO: 6
118-120
179-183
267-269
298-299

SEQ ID NO: 8
119-121
180-184
268-270
299-300

SEQ ID NO: 10
118-120
179-183
267-269
298-299

SEQ ID NO: 12
119-121
181-185
269-271
300-301

SEQ ID NO: 14
118-120
186-190
272-274
303-304

SEQ ID NO: 16
118-120
186-190
272-274
303-304

SEQ ID NO: 18
117-119
180-184
270-272
301-302

SEQ ID NO: 20
133-135
193-197
282-284
313-314

SEQ ID NO: 22
118-120
181-185
171-173
302-303

SEQ ID NO: 24
117-119
180-184
270-272
301-302

SEQ ID NO: 30
118-120
179-183
267-269
298-299

SEQ ID NO: 54
117-119
180-184
270-272
301-302

SEQ ID NO: 56
118-120
186-190
272-274
303-304

SEQ ID NO: 58
118-120
186-190
272-274
303-304

SEQ ID NO. 60
118-120
186-190
272-274
303-304

SEQ ID NO. 62
119-121
187-191
273-275
304-305



a = Conserved motifs defined by Vincent et al., supra used to define the signature motif.

b = an additional motif identified herein useful in further defining the signature motif defined by Vincent et al., supra.










































Alternatively, a contiguous signature motif (SEQ ID NO: 53) comprising the 4 conserved motifs (RGQ, GXSQG, LXD, and HE; Amino acids residues 118-299 of SEQ ID NO: 2) may also be used as a contiguous signature motif to identify CE-7 carbohydrate esterases. As such, suitable enzymes expected to have perhydrolase activity may also be identified as having at least 30% amino acid identify, preferably at least 36%, more preferably at least 40%, even more preferably at least 50%, yet more preferably at least 60%, yet even more preferably at least 70%, yet even more preferably at least 80%, yet even more preferably at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity to SEQ ID NO: 53 (the 4 conserved motifs found in CE-7 carbohydrate esterases are underlined).






(SEQ ID NO: 53)


RGQ QSSEDTSISLHGHALGWMTKGILDKDTYYYRGVYLDAVRALEVISSFDEVDETRIG




VT GGSQG GGLTIAAAALSDIPKAAVADYPYLSNFERAIDVALEQPYLEINSFFRRNGSPE



TEVQAMKTLSYFDIMNLADRVKVPVLMSIG LID KVTPPSTVFAAYNHLETEKELKVYRY



FG HE .















A comparison using the contiguous signature sequence against the present CE-7 esterases having perhydrolase activity is provided in Table 4. BLASTP using default parameters was used.





TABLE 4



Percent Amino Acid Identity of Various CE-7 Carbohydrate

Esterases having Perhydrolysis Activity Versus the

Contiguous Signature Sequence (SEQ ID NO: 53).







Perhydrolase
% Identity using
E-score


Sequence
BLASTP
(expected)










SEQ ID NO: 2
100
3e−92


SEQ ID NO: 4
98
6e−91


SEQ ID NO: 6
98
4e−98


SEQ ID NO: 8
78
1e−78


SEQ ID NO: 10
80
3e−76


SEQ ID NO: 12
63
2e−56


SEQ ID NO: 14
51
1e−41


SEQ ID NO: 16
50
6e−35


SEQ ID NO: 24
36
7e−21


SEQ ID NO: 30
99
2e−90


SEQ ID NO: 54
40
2e−26


SEQ ID NO: 56
40
3e−30


SEQ ID NO: 58
46
6e−35


SEQ ID NO. 61
46
6e−35


SEQ ID NO. 62
48
9e−36










































Alternatively, the percent amino acid identity to the complete length of one or more of the present perhydrolases may also be used. Accordingly, suitable enzymes having an amino acid sequence having at least 30%, preferably at least 33%, preferably at least 40%, preferably at least 40%, more preferably at least 50%, more preferably at least 60%, more preferably at least 70%, even more preferably at least 80%, yet even more preferably at least 90%, and most preferably at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% amino acid identity to SEQ ID NO: 2. In a further embodiment, suitable perhydrolase catalysts comprise an amino acid sequence selected from the group consisting of SEQ ID NO: 2, SEQ ID NO: 4, SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 10, SEQ ID NO: 12, SEQ ID NO: 14, SEQ ID NO: 16, SEQ ID NO: 18, SEQ ID NO: 20, SEQ ID NO: 22, SEQ ID NO: 24, SEQ ID NO: 30, SEQ ID NO: 54, SEQ ID NO: 56, SEQ ID NO: 58, SEQ ID NO: 60, SEQ ID NO: 62. In preferred embodiments, suitable enzymes having perhydrolase activity having at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% amino acid identity to SEQ ID NO: 2 or to SEQ ID NO: 10 or to SEQ ID NO: 14 or to SEQ ID NO: 16 may be used.
Suitable perhydrolase enzymes may also include enzymes having one or more deletions, substitutions, and/or insertions to one of the present perhydrolase enzymes (e.g. SEQ ID NOs. 2, 10, 14, and 16). As shown in Table 2, CE-7 carbohydrates esterases having perhydrolase activity share as little as 32% overall amino acid identity. Based on the data provided in the present examples, additional enzymes having perhydrolase activity belonging to the CE-7 carbohydrate esterase family may have even lower percent identity, so long as the enzyme retains the conserved signature motif. As such, the numbers of deletions, substitutions, and/or insertions may vary so long as the conserved signature motifs (see Table 3) are found in their relative positions within the enzyme.
An enzyme catalyst comprising a variant enzyme having an amino acid sequence derived from one or more of the present sequences provided herein may also be used in the present processes. U.S. Provisional Patent Application No. 61/102,520 to DiCosimo et al. (incorporated herein by reference) describes enzyme catalysts having improved perhydrolysis activity. More specifically, DiCosimo et al. teaches how certain amino acid substitutions (alanine, valine, serine or threonine) to a key cysteine residue found within several Thermotoga acetyl xylan esterases increases perhydrolysis activity of the variant enzyme when compared to the wild-type acetyl xylan esterase. Because of the high homology between acetyl xylan esterases across the Thermotoga genus, it is expected that a substitution to the cysteine residue with an alanine, valine, serine, or threonine in any Thermotoga genus will produce similar results.
In one embodiment, the present processes may use variant Thermotoga -derived enzymes having at least 95% sequence identity (or, in various embodiments, 96%, 97%, 98%, or 99% sequence identity), based on the CLUSTAL method (such as CLUSTALW) of alignment with pairwise alignment default parameters of KTUPLE=1, GAP PENALTY=3, WINDOW=5 and DIAGONALS SAVED=5, when compared to SEQ ID NOs: 69, 70, 71, 72, or 73, provided that a substitution to amino acid 277 of SEQ ID NOs: 69, 70, 71, 72, or 73 is selected from the group consisting of serine, threonine, valine, and alanine.
In a more specific embodiment, the present processes may use a variant Thermotoga enzyme comprising an amino acid sequence selected from the group consisting of SEQ ID NOs: 69, 70, 71, 72, and 73 provided the amino acid residue 277 is selected from the group consisting of serine, threonine, valine, and alanine.
In a further specific embodiment, the present processes may use a variant Thermotoga neapolitana enzyme comprising an amino acid sequence SEQ ID NO: 69 wherein amino acid residue 277 is substituted with an amino acid selected from the group consisting of serine, threonine, valine, and alanine.
In a further specific embodiment, the present processes may use a variant Thermotoga maritima enzyme comprising an amino acid sequence SEQ ID NO: 70 wherein amino acid residue 277 is substituted with an amino acid selected from the group consisting of serine, threonine, valine, and alanine.
Additionally, it is well within one of skill in the art to identity suitable enzymes according to the structural similarity found within the corresponding nucleic acid sequence. Hybridization techniques can be used to identity similar gene sequences. Accordingly, suitable perhydrolase catalysts useful in the present processes comprise an amino acid sequence encoded by a nucleic acid molecule that hybridizes under stringent conditions to a nucleic acid molecule having a nucleic acid sequence selected from the group consisting of SEQ ID NO: 1; SEQ ID NO: 3; SEQ ID NO: 5, SEQ ID NO: 7, SEQ ID NO: 9, SEQ ID NO: 11, SEQ ID NO: 13, SEQ ID NO: 15, SEQ ID NO: 17, SEQ ID NO: 19, SEQ ID NO: 21, SEQ ID NO: 23, SEQ ID NO: 29, SEQ ID NO: 55, SEQ ID NO: 57, SEQ ID NO: 59, and SEQ ID NO: 61.
In another embodiment, the perhydrolase catalyst comprises an enzyme having an amino acid sequence encoded by a nucleic acid molecule that hybridizes under stringent conditions to a nucleic acid sequence selected from the group consisting of SEQ ID NO: 1, SEQ ID NO: 9, SEQ ID NO: 13, and SEQ ID NO: 15.
The present method produces industrially useful, efficacious concentrations of peracids in situ under aqueous reaction conditions using the perhydrolase activity of an enzyme belonging to the CE-7 family of carbohydrate esterases. In one embodiment, the enzyme having perhydrolase activity is also classified structurally and functionally as a cephalosporin C deacetylase (CAH). In another embodiment, the enzyme having perhydrolase activity is classified structurally and functionally as an acetyl xylan esterase (AXE).
The peracids produced are quite reactive and may decrease in concentration over extended periods of time, depending on variables that include, but are not limited to, temperature and pH. As such, it may be desirable to keep the various reaction components separated, especially for liquid formulations. In one aspect, the hydrogen peroxide source is separate from either the substrate or the perhydrolase catalyst, preferably from both. This can be accomplished using a variety of techniques including, but not limited to, the use of multicompartment chambered dispensers (U.S. Pat. No. 4,585,150) and at the time of use physically combining the perhydrolase catalyst with an inorganic peroxide and the present substrates to initiate the aqueous enzymatic perhydrolysis reaction. The perhydrolase catalyst may optionally be immobilized within the body of reaction chamber or separated (e.g., filtered, etc.) from the reaction product comprising the peracid prior to contacting the surface and/or object targeted for treatment. The perhydrolase catalyst may be in a liquid matrix or in a solid form (i.e., powdered, tablet) or embedded within a solid matrix that is subsequently mixed with the substrates to initiate the enzymatic perhydrolysis reaction. In a further aspect, the perhydrolase catalyst may be contained within a dissolvable or porous pouch that may be added to the aqueous substrate matrix to initiate enzymatic perhydrolysis. In an additional further aspect, a powder comprising the enzyme catalyst is suspended in the substrate (e.g., triacetin), and at time of use is mixed with a source of peroxygen in water.
HPLC Assay Method for Determining the Concentration of Peracid and Hydrogen Peroxide.
A variety of analytical methods can be used in the present method to analyze the reactants and products including, but not limited to, titration, high performance liquid chromatography (HPLC), gas chromatography (GC), mass spectroscopy (MS), capillary electrophoresis (CE), the analytical procedure described by U. Karst et al., ( Anal. Chem., 69(17):3623-3627 (1997)), and the 2,2′-azino-bis(3-ethylbenzothazoline)-6-sulfonate (ABTS) assay (S. Minning, et al., Analytica Chimica Acta 378:293-298 (1999) and WO 2004/058961 A1) as described in the present examples.
Determination of Minimum Biocidal Concentration of Peracids
The method described by J. Gabrielson, et al. ( J. Microbiol. Methods 50: 63-73 (2002)) can be employed for determination of the Minimum Biocidal Concentration (MBC) of peracids, or of hydrogen peroxide and enzyme substrates. The assay method is based on XTT reduction inhibition, where XTT ((2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-5-[(phenylamino)carbonyl]-2H-tetrazolium, inner salt, monosodium salt) is a redox dye that indicates microbial respiratory activity by a change in optical density (OD) measured at 490 nm or 450 nm. However, there are a variety of other methods available for testing the activity of disinfectants and antiseptics including, but not limited to, viable plate counts, direct microscopic counts, dry weight, turbidity measurements, absorbance, and bioluminescence (see, for example Brock, Semour S., Disinfection, Sterilization, and Preservation, 5 th edition, Lippincott Williams & Wilkins, Philadelphia, Pa., USA; 2001).
Uses of Enzymatically Prepared Peracid Compositions
The enzyme catalyst-generated peracid produced according to the present methods can be used in a variety of hard surface/inanimate object applications for reduction of concentrations of microbial, fungal, prion-related, and viral contamination, such as decontamination of medical instruments (e.g., endoscopes), textiles (e.g., garments, carpets), food preparation surfaces, food storage and food-packaging equipment, materials used for the packaging of food products, chicken hatcheries and grow-out facilities, animal enclosures, and spent process waters that have microbial and/or virucidal activity. The enzyme-generated peracids may be used in formulations designed to inactivate prions (e.g. certain proteases) to additionally provide biocidal activity. In a preferred aspect, the present peracid compositions are particularly useful as a disinfecting agent for non-autoclavable medical instruments and food packaging equipment. As the peracid-containing formulation may be prepared using GRAS or food-grade components (enzyme, enzyme substrate, hydrogen peroxide, and buffer), the enzyme-generated peracid may also be used for decontamination of animal carcasses, meat, fruits and vegetables, or for decontamination of prepared foods. The enzyme-generated peracid may be incorporated into a product whose final form is a powder, liquid, gel, film, solid or aerosol. The enzyme-generated peracid may be diluted to a concentration that still provides an efficacious decontamination.
The compositions comprising an efficacious concentration of peracid can be used to disinfect surfaces and/or objects contaminated (or suspected of being contaminated) with viable pathogenic microbial contaminants by contacting the surface or object with the products produced by the present processes. As used herein, “contacting” refers to placing a disinfecting composition comprising an effective concentration of peracid in contact with the surface or inanimate object suspected of contamination with a disease-causing entity for a period of time sufficient to clean and disinfect. Contacting includes spraying, treating, immersing, flushing, pouring on or in, mixing, combining, painting, coating, applying, affixing to and otherwise communicating a peracid solution or composition comprising an efficacious concentration of peracid, or a solution or composition that forms an efficacious concentration of peracid, with the surface or inanimate object suspected of being contaminated with a concentration of a microbial population. The disinfectant compositions may be combined with a cleaning composition to provide both cleaning and disinfection. Alternatively, a cleaning agent (e.g., a surfactant or detergent) may be incorporated into the formulation to provide both cleaning and disinfection in a single composition.
The compositions comprising an efficacious concentration of peracid can also contain at least one additional antimicrobial agent, combinations of prion-degrading proteases, a virucide, a sporicide, or a biocide. Combinations of these agents with the peracid produced by the claimed processes can provide for increased and/or synergistic effects when used to clean and disinfect surfaces and/or objects contaminated (or suspected of being contaminated) with pathogenic microorganisms, spores, viruses, fungi, and/or prions. Suitable antimicrobial agents include carboxylic esters (e.g., p-hydroxy alkyl benzoates and alkyl cinnamates), sulfonic acids (e.g., dodecylbenzene sulfonic acid), iodo-compounds or active halogen compounds (e.g., elemental halogens, halogen oxides (e.g., NaOCl, HOCl, HOBr, ClO 2 ), iodine, interhalides (e.g., iodine monochloride, iodine dichloride, iodine trichloride, iodine tetrachloride, bromine chloride, iodine monobromide, or iodine dibromide), polyhalides, hypochlorite salts, hypochlorous acid, hypobromite salts, hypobromous acid, chloro- and bromo-hydantoins, chlorine dioxide, and sodium chlorite), organic peroxides including benzoyl peroxide, alkyl benzoyl peroxides, ozone, singlet oxygen generators, and mixtures thereof, phenolic derivatives (e.g., o-phenyl phenol, o-benzyl-p-chlorophenol, tert-amyl phenol and C 1 -C 6 alkyl hydroxy benzoates), quaternary ammonium compounds (e.g., alkyldimethylbenzyl ammonium chloride, dialkyldimethyl ammonium chloride and mixtures thereof), and mixtures of such antimicrobial agents, in an amount sufficient to provide the desired degree of microbial protection. Effective amounts of antimicrobial agents include about 0.001 wt % to about 60 wt % antimicrobial agent, about 0.01 wt % to about 15 wt % antimicrobial agent, or about 0.08 wt % to about 2.5 wt % antimicrobial agent.
In one aspect, the peracids formed by the present process can be used to reduce the concentration of viable microbial contaminants (e.g. a viable microbial population) when applied on and/or at a locus. As used herein, a “locus” comprises part or all of a target surface suitable for disinfecting or bleaching. Target surfaces include all surfaces that can potentially be contaminated with microorganisms, viruses, spores, fungi, prions or combinations thereof. Non-limiting examples include equipment surfaces found in the food or beverage industry (such as tanks, conveyors, floors, drains, coolers, freezers, equipment surfaces, walls, valves, belts, pipes, drains, joints, crevasses, combinations thereof, and the like); building surfaces (such as walls, floors and windows); non-food-industry related pipes and drains, including water treatment facilities, pools and spas, and fermentation tanks; hospital or veterinary surfaces (such as walls, floors, beds, equipment, (such as endoscopes) clothing worn in hospital/veterinary or other healthcare settings, including clothing, scrubs, shoes, and other hospital or veterinary surfaces); restaurant surfaces; bathroom surfaces; toilets; clothes and shoes; surfaces of barns or stables for livestock, such as poultry, cattle, dairy cows, goats, horses and pigs; hatcheries for poultry or for shrimp; and pharmaceutical or biopharmaceutical surfaces (e.g., pharmaceutical or biopharmaceutical manufacturing equipment, pharmaceutical or biopharmaceutical ingredients, pharmaceutical or biopharmaceutical excipients). Additional hard surfaces also include food products, such as beef, poultry, pork, vegetables, fruits, seafood, combinations thereof, and the like. The locus can also include water absorbent materials such as infected linens or other textiles. The locus also includes harvested plants or plant products including seeds, corms, tubers, fruit, and vegetables, growing plants, and especially crop growing plants, including cereals, leaf vegetables and salad crops, root vegetables, legumes, berried fruits, citrus fruits and hard fruits.
Non-limiting examples of hard surface materials are metals (e.g., steel, stainless steel, chrome, titanium, iron, copper, brass, aluminum, and alloys thereof), minerals (e.g., concrete), polymers and plastics (e.g., polyolefins, such as polyethylene, polypropylene, polystyrene, poly(meth)acrylate, polyacrylonitrile, polybutadiene, poly(acrylonitrile, butadiene, styrene), poly(acrylonitrile, butadiene), acrylonitrile butadiene; polyesters such as polyethylene terephthalate; and polyamides such as nylon). Additional surfaces include brick, tile, ceramic, porcelain, wood, vinyl, linoleum, and carpet.
Peracids have also been reported to be useful in preparing bleaching compositions for laundry detergent applications (U.S. Pat. No. 3,974,082; U.S. Pat. No. 5,296,161; and U.S. Pat. No. 5,364,554). Some bleaching applications may require a controlled level of bleaching activity for optimal performance. In an additional aspect, the peracids formed by the present process can be used for bleaching of laundry or textiles, where similar limitations to the concentration of peracid generated for bleaching are also desirable.
Recombinant Microbial Expression
The genes and gene products of the instant sequences may be produced in heterologous host cells, particularly in the cells of microbial hosts. Preferred heterologous host cells for expression of the instant genes and nucleic acid molecules are microbial hosts that can be found within the fungal or bacterial families and which grow over a wide range of temperature, pH values, and solvent tolerances. For example, it is contemplated that any of bacteria, yeast, and filamentous fungi may suitably host the expression of the present nucleic acid molecules. The perhydrolase may be expressed intracellularly, extracellularly, or a combination of both intracellularly and extracellularly, where extracellular expression renders recovery of the desired protein from a fermentation product more facile than methods for recovery of protein produced by intracellular expression. Transcription, translation and the protein biosynthetic apparatus remain invariant relative to the cellular feedstock used to generate cellular biomass; functional genes will be expressed regardless. Examples of host strains include, but are not limited to bacterial, fungal or yeast species such as Aspergillus, Trichoderma, Saccharomyces, Pichia, Phaffia, Candida, Hansenula, Yarrowia, Salmonella, Bacillus, Acinetobacter, Zymomonas, Agrobacterium, Dythrobacter, Chlorobium, Chromatium, Flavobacterium, Cytophaga, Rhodobacter, Rhodococcus, Streptomyces, Brevibacterium, Corynebacteria, Mycobacterium, Deinococcus, Escherichia, Erwinia, Pantoea, Pseudomonas, Sphingomonas, Methylomonas, Methylobacter, Methylococcus, Methylosinus, Methylomicrobium, Methylocystis, Alcaligenes, Synechocystis, Synechococcus, Anabaena, Thiobacillus, Methanobacterium, Klebsiella , and Myxococcus . In one embodiment, bacterial host strains include Escherichia, Bacillus , and Pseudomonas . In a preferred embodiment, the bacterial host cell is Escherichia coli.
Large-scale microbial growth and functional gene expression may use a wide range of simple or complex carbohydrates, organic acids and alcohols or saturated hydrocarbons, such as methane or carbon dioxide in the case of photosynthetic or chemoautotrophic hosts, the form and amount of nitrogen, phosphorous, sulfur, oxygen, carbon or any trace micronutrient including small inorganic ions. The regulation of growth rate may be affected by the addition, or not, of specific regulatory molecules to the culture and which are not typically considered nutrient or energy sources.
Vectors or cassettes useful for the transformation of suitable host cells are well known in the art. Typically the vector or cassette contains sequences directing transcription and translation of the relevant gene, a selectable marker, and sequences allowing autonomous replication or chromosomal integration. Suitable vectors comprise a region 5′ of the gene which harbors transcriptional initiation controls and a region 3′ of the DNA fragment which controls transcriptional termination. It is most preferred when both control regions are derived from genes homologous to the transformed host cell and/or native to the production host, although such control regions need not be so derived.
Initiation control regions or promoters, which are useful to drive expression of the present cephalosporin C deacetylase coding region in the desired host cell are numerous and familiar to those skilled in the art. Virtually any promoter capable of driving these genes is suitable for the present invention including but not limited to CYC1, HIS3, GAL1, GAL10, ADH1, PGK, PHO5, GAPDH, ADC1, TRP1, URA3, LEU2, ENO, TPI (useful for expression in Saccharomyces ); AOX1 (useful for expression in Pichia ); and lac, ara, tet, trp, lP L , lP R , T7, tac, and trc (useful for expression in Escherichia coli ) as well as the amy, apr, npr promoters and various phage promoters useful for expression in Bacillus.
Termination control regions may also be derived from various genes native to the preferred host cell. In one embodiment, the inclusion of a termination control region is optional. In another embodiment, the chimeric gene includes a termination control region derived the preferred host cell.
Industrial Production
A variety of culture methodologies may be applied to produce the present perhydrolase catalysts. For example, large-scale production of a specific gene product overexpressed from a recombinant microbial host may be produced by both batch and continuous culture methodologies.
A classical batch culturing method is a closed system where the composition of the media is set at the beginning of the culture and not subject to artificial alterations during the culturing process. Thus, at the beginning of the culturing process, the media is inoculated with the desired organism or organisms and growth or metabolic activity may occur without adding anything further to the system. Typically, however, a “batch” culture is batch with respect to the addition of carbon source and attempts are often made to control factors such as pH and oxygen concentration. In batch systems the metabolite and biomass compositions of the system change constantly up to the time the culture is terminated. Within batch cultures cells moderate through a static lag phase to a high growth log phase and finally to a stationary phase where growth rate is diminished or halted. If untreated, cells in the stationary phase will eventually die. Cells in log phase are often responsible for the bulk of production of end product or intermediate in some systems. Stationary or post-exponential phase production can be obtained in other systems.
A variation on the standard batch system is the fed-batch system. Fed-batch culture processes are also suitable in the present invention and comprise a typical batch system except that the substrate is added in increments as the culture progresses. Fed-batch systems are useful when catabolite repression is apt to inhibit the metabolism of the cells and where it is desirable to have limited amounts of substrate in the media. Measurement of the actual substrate concentration in fed-batch systems is difficult and is estimated on the basis of the changes of measurable factors such as pH, dissolved oxygen and the partial pressure of waste gases such as CO 2 . Batch and fed-batch culturing methods are common and well known in the art and examples may be found in Thomas D. Brock in Biotechnology: A Textbook of Industrial Microbiology , Second Edition, Sinauer Associates, Inc., Sunderland, Mass. (1989) and Deshpande, Mukund V., Appl. Biochem. Biotechnol., 36:227 (1992).
Commercial production of the desired perhydrolase catalysts may also be accomplished with a continuous culture. Continuous cultures are an open system where a defined culture media is added continuously to a bioreactor and an equal amount of conditioned media is removed simultaneously for processing. Continuous cultures generally maintain the cells at a constant high liquid phase density where cells are primarily in log phase growth. Alternatively, continuous culture may be practiced with immobilized cells where carbon and nutrients are continuously added and valuable products, by-products or waste products are continuously removed from the cell mass. Cell immobilization may be performed using a wide range of solid supports composed of natural and/or synthetic materials.
Continuous or semi-continuous culture allows for the modulation of one factor or any number of factors that affect cell growth or end product concentration. For example, one method will maintain a limiting nutrient such as the carbon source or nitrogen level at a fixed rate and allow all other parameters to moderate. In other systems a number of factors affecting growth can be altered continuously while the cell concentration, measured by media turbidity, is kept constant. Continuous systems strive to maintain steady state growth conditions and thus the cell loss due to media being drawn off must be balanced against the cell growth rate in the culture. Methods of modulating nutrients and growth factors for continuous culture processes as well as techniques for maximizing the rate of product formation are well known in the art of industrial microbiology and a variety of methods are detailed by Brock, supra.
Fermentation media in the present invention must contain suitable carbon substrates. Suitable substrates may include but are not limited to monosaccharides such as glucose and fructose, disaccharides such as lactose or sucrose, polysaccharides such as starch or cellulose or mixtures thereof and unpurified mixtures from renewable feedstocks such as cheese whey permeate, cornsteep liquor, sugar beet molasses, and barley malt. Additionally, the carbon substrate may also be one-carbon substrates such as carbon dioxide, methane or methanol (for example, when the host cell is a methylotrophic microorganism). Similarly, various species of Candida will metabolize alanine or oleic acid (Sutter et al., Arch. Microbiol., 153:485-489 (1990)). Hence, it is contemplated that the source of carbon utilized in the present invention may encompass a wide variety of carbon-containing substrates and will only be limited by the choice of organism.
Recovery of the desired perhydrolase catalysts from a batch or fed batch fermentation, or continuous culture, may be accomplished by any of the methods that are known to those skilled in the art. For example, when the perhydrolase catalyst is produced intracellularly, the cell paste is separated from the culture medium by centrifugation or membrane filtration, optionally washed with water or an aqueous buffer at a desired pH, then a suspension of the cell paste in an aqueous buffer at a desired pH is homogenized to produce a cell extract containing the desired perhydrolase catalyst. The cell extract may optionally be filtered through an appropriate filter aid such as celite or silica to remove cell debris prior to a heat-treatment step to precipitate undesired protein from the perhydrolase catalyst solution. The solution containing the desired perhydrolase catalyst may then be separated from the precipitated cell debris and protein by membrane filtration or centrifugation, and the resulting partially-purified perhydrolase catalyst solution concentrated by additional membrane filtration, then optionally mixed with an appropriate carrier (for example, maltodextrin, phosphate buffer, citrate buffer, or mixtures thereof) and spray-dried to produce a solid powder comprising the desired perhydrolase catalyst.
Applicants specifically incorporate the entire contents of all cited references in this disclosure. Further, when an amount, concentration, or other value or parameter is given either as a range, preferred range, or a list of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. Where a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range. It is not intended that the scope be limited to the specific values recited when defining a range.
General Methods
The following examples are provided to demonstrate preferred aspects of the invention. It should be appreciated by those of skill in the art that the techniques disclosed in the examples which follow represent techniques discovered by the inventor to function well in the practice of the invention, and thus can be considered to constitute preferred modes for its practice. However, those of skill in the art should, in light of the present disclosure, appreciate that many changes can be made in the specific embodiments which are disclosed and still obtain a like or similar result without departing from the spirit and scope of the invention.
All reagents and materials were obtained from DIFCO Laboratories (Detroit, Mich.), GIBCO/BRL (Gaithersburg, Md.), TCI America (Portland, Oreg.), Roche Diagnostics Corporation (Indianapolis, Ind.) or Sigma/Aldrich Chemical Company (St. Louis, Mo.), unless otherwise specified.
The following abbreviations in the specification correspond to units of measure, techniques, properties, or compounds as follows: “sec” or “s” means second(s), “min” means minute(s), “h” or “hr” means hour(s), “4” means microliter(s), “mL” means milliliter(s), “L” means liter(s), “mM” means millimolar, “M” means molar, “mmol” means millimole(s), “ppm” means part(s) per million, “wt” means weight, “wt %” means weight percent, “g” means gram(s), “μg” means microgram(s), “ng” means nanogram(s), “g” means gravity, “HPLC” means high performance liquid chromatography, “dd H 2 O” means distilled and deionized water, “dcw” means dry cell weight, “ATCC” or “ATCC®” means the American Type Culture Collection (Manassas, Va.), “U” means unit(s) of perhydrolase activity, “rpm” means revolution(s) per minute, and “EDTA” means ethylenediaminetetraacetic acid.
Example 1
Construction of a KatG Catalase Disrupted E. coli Strain
The kanamycin resistance gene (kan; SEQ ID NO: 35) was amplified from the plasmid pKD13 (SEQ ID NO: 36) by PCR (0.5 min at 94° C., 0.5 min at 55° C., 1 min at 70° C., 30 cycles) using primers identified as SEQ ID NO: 37 and SEQ ID NO: 38 to generate the PCR product identified as SEQ ID NO: 39. The katG nucleic acid sequence is provided as SEQ ID NO: 40 and the corresponding amino acid sequence is SEQ ID NO: 41. E. coli MG1655 (ATCC® 47076™) was transformed with the temperature-sensitive plasmid pKD46 (SEQ ID NO: 42), which contains the λ-Red recombinase genes (Datsenko and Wanner, 2000 , PNAS USA 97:6640-6645), and selected on LB-amp plates for 24 h at 30° C. MG1655/pKD46 was transformed with 50-500 ng of the PCR product by electroporation (BioRad Gene Pulser, 0.2 cm cuvette, 2.5 kV, 200 W, 25 uF), and selected on LB-kan plates for 24 h at 37° C. Several colonies were streaked onto LB-kan plates and incubated overnight at 42° C. to cure the pKD46 plasmid. Colonies were checked to confirm a phenotype of kanR/ampS. Genomic DNA was isolated from several colonies using the PUREGENE® DNA purification system, and checked by PCR to confirm disruption of the katG gene using primers identified as SEQ ID NO: 43 and SEQ ID NO: 44. Several katG-disrupted strains were transformed with the temperature-sensitive plasmid pCP20 (SEQ ID NO: 45), which contains the FLP recombinase, used to excise the kan gene, and selected on LB-amp plates for 24 h at 37° C. Several colonies were streaked onto LB plates and incubated overnight at 42° C. to cure the pCP20 plasmid. Two colonies were checked to confirm a phenotype of kanS/ampS, and called MG 1655 KatG1 and MG1655 KatG2.
Example 2
Construction of a KatE Catalase Disrupted E. coli Strain
The kanamycin resistance gene (SEQ ID NO: 35) was amplified from the plasmid pKD13 (SEQ ID NO: 36) by PCR (0.5 min at 94° C., 0.5 min at 55° C., 1 min at 70° C., 30 cycles) using primers identified as SEQ ID NO: 46 and SEQ ID NO: 47 to generate the PCR product identified as SEQ ID NO: 48. The katE nucleic acid sequence is provided as SEQ ID NO: 49 and the corresponding amino acid sequence is SEQ ID NO: 50. E. coli MG1655 (ATCC® 47076™) was transformed with the temperature-sensitive plasmid pKD46 (SEQ ID NO: 42), which contains the λ-Red recombinase genes, and selected on LB-amp plates for 24 h at 30° C. MG1655/pKD46 was transformed with 50-500 ng of the PCR product by electroporation (BioRad Gene Pulser, 0.2 cm cuvette, 2.5 kV, 200 W, 25 uF), and selected on LB-kan plates for 24 h at 37° C. Several colonies were streaked onto LB-kan plates and incubated overnight at 42° C. to cure the pKD46 plasmid. Colonies were checked to confirm a phenotype of kanR/ampS. Genomic DNA was isolated from several colonies using the PUREGENE DNA purification system, and checked by PCR to confirm disruption of the katE gene using primers identified as SEQ ID NO: 51 and SEQ ID NO: 52. Several katE-disrupted strains were transformed with the temperature-sensitive plasmid pCP20 (SEQ ID NO: 45), which contains the FLP recombinase, used to excise the kan gene, and selected on LB-amp plates for 24 h at 37° C. Several colonies were streaked onto LB plates and incubated, overnight at 42° C. to cure the pCP20 plasmid. Two colonies were checked to confirm a phenotype of kanS/ampS, and called MG1655 KatE1 and MG1655 KatE2
Example 3
Construction of a KatG Catalase and KatE Catalase Disrupted E. coli Strain (KLP18)
The kanamycin resistance gene (SEQ ID NO: 35) was amplified from the plasmid pkD13 (SEQ ID NO: 36) by PCR (0.5 min at 94° C., 0.5 min at 55° C., 1 min at 70° C., 30 cycles) using primers identified as SEQ ID NO: 46 and SEQ ID NO: 47 to generate the PCR product identified as SEQ ID NO: 48. E. coli MG1655 KatG1 (EXAMPLE 13) was transformed with the temperature-sensitive plasmid pKD46 (SEQ ID NO: 42), which contains the λ-Red recombinase genes, and selected on LB-amp plates for 24 h at 30° C. MG1655 KatG1/pKD46 was transformed with 50-500 ng of the PCR product by electroporation (BioRad Gene Pulser, 0.2 cm cuvette, 2.5 kV, 200 W, 25 uF), and selected on LB-kan plates for 24 h at 37° C. Several colonies were streaked onto LB-kan plates and incubated overnight at 42° C. to cure the pKD46 plasmid. Colonies were checked to confirm a phenotype of kanR/ampS. Genomic DNA was isolated from several colonies using the PUREGENE® DNA purification system, and checked by PCR to confirm disruption of the katE gene using primers identified as SEQ ID NO: 51 and SEQ ID NO: 52. Several katE-disrupted strains (ΔkatE) were transformed with the temperature-sensitive plasmid pCP20 (SEQ ID NO: 45), which contains the FLP recombinase, used to excise the kan gene, and selected on LB-amp plates for 24 h at 37° C. Several colonies were streaked onto LB plates and incubated overnight at 42° C. to cure the pCP20 plasmid. Two colonies were checked to confirm a phenotype of kanS/ampS, and called MG1655 KatG1KatE18.1 and MG1655 KatG1KatE23. MG1655 KatG1KatE18.1 is designated E. coli KLP18.
Example 4
Cloning and Expression of Perhydrolase from Thermotoga neapolitana
The gene encoding acetyl xylan esterase from Thermotoga neapolitana as reported in GENBANK® (accession #U58632) was synthesized using codons optimized for expression in E. coli (DNA 2.0, Menlo Park, Calif.). The gene was subsequently amplified by PCR (0.5 min at 94° C., 0.5 min at 55° C., 1 min at 70° C., 30 cycles) using primers identified as SEQ ID NO: 66 and SEQ ID NO: 67. The resulting nucleic acid product (SEQ ID NO: 68) was subcloned into pTrcHis2-TOPO® to generate the plasmid identified as pSW196. The plasmid pSW196 was used to transform E. coli KLP18 to generate the strain KLP18/pSW196. KLP18/pSW196 was grown in LB media at 37° C. with shaking up to OD600 nm=0.4-0.5, at which time IPTG was added to a final concentration of 1 mM, and incubation continued for 2-3 h. Cells were harvested by centrifugation and SDS-PAGE was performed to confirm expression of the perhydrolase at 20-40% of total soluble protein.
Example 5
Cloning and Expression of Perhydrolase from Thermotoga maritima MSB8
The gene encoding acetyl xylan esterase from Thermotoga maritima MSB8 as reported in GENBANK® (accession #NP — 227893.1) was synthesized (DNA 2.0, Menlo Park, Calif.). The gene was subsequently amplified by PCR (0.5 min @94° C., 0.5 min @55° C., 1 min @70° C., 30 cycles) using primers identified as SEQ ID NO: 63 and SEQ ID NO: 64. The resulting nucleic acid product (SEQ ID NO: 65) was cut with restriction enzymes PstI and XbaI and subcloned between the PstI and XbaI sites in pUC19 to generate the plasmid identified as pSW207. The plasmid pSW207 was used to transform E. coli KLP18 to generate the strain identified as KLP18/pSW207. KLP18/pSW207 was grown in LB media at 37 C with shaking up to OD600 nm=0.4-0.5, at which time IPTG was added to a final concentration of 1 mM, and incubation continued for 2-3 hrs. Cells were harvested by centrifugation and SDS-PAGE was performed to confirm expression of the perhydrolase enzyme at 20-40% of total soluble protein.
Example 6
Cloning and Expression of Perhydrolase from Bacillus subtilis ATCC® 31954™
Genomic DNA was isolated from Bacillus subtilis ATCC® 31954™ using the PUREGENE® DNA purification system (Gentra Systems, Minneapolis Minn.). The perhydrolase gene was amplified from the genomic DNA by PCR (0.5 min at 94° C., 0.5 min at 55° C., 1 min at 70° C., 30 cycles) using primers identified as SEQ ID NO: 25 and SEQ ID NO: 26. The resulting nucleic acid product (SEQ ID NO: 27) was cut with restriction enzymes PstI and XbaI and subcloned between the PstI and XbaI sites in pUC19 to generate the plasmid identified as pSW194. The plasmid pSW194 was used to transform E. coli KLP18 to generate the strain identified as KLP18/pSW194. KLP18/pSW194 was grown in LB media at 37° C. with shaking up to OD 600nm =0.4-0.5, at which time IPTG was added to a final concentration of 1 mM, and incubation continued for 2-3 h. Cells were harvested by centrifugation and SDS-PAGE was performed to confirm expression of the perhydrolase at 20-40% of total soluble protein.
Example 7
Cloning and Expression of Perhydrolase from Bacillus subtilis BE1010
Genomic DNA was isolated from Bacillus subtilis BE1010 (Payne and Jackson 1991 J. Bacteriol. 173:2278-2282) using the PUREGENE® DNA purification system (Gentra Systems). The perhydrolase gene was amplified from the genomic DNA by PCR (0.5 min at 94° C., 0.5 min at 55° C., 1 min at 70° C., 30 cycles) using primers identified as SEQ ID NO: 25 and SEQ ID NO: 26. The resulting nucleic acid product (SEQ ID NO: 28) was cut with restriction enzymes PstI and XbaI and subcloned between the PstI and XbaI sites in pUC19 to generate the plasmid identified as pSW189. The plasmid pSW189 was used to transform E. coli KLP18 to generate the strain identified as KLP18/pSW189. KLP18/pSW189 was grown in LB media at 37° C. with shaking up to OD 600nm =0.4-0.5, at which time IPTG was added to a final concentration of 1 mM, and incubation continued for 2-3 h. Cells were harvested by centrifugation and SDS-PAGE was performed to confirm expression of the perhydrolase at 20-40% of total soluble protein.
Example 8
Cloning and Expression of Perhydrolase from Bacillus pumilus PS213
The gene encoding acetyl xylan esterase (axe1) from B. pumilus PS213 as reported in GENBANK® (accession #AJ249957) was synthesized using codons optimized for expression in E. coli (DNA 2.0, Menlo Park Calif.). The gene was subsequently amplified by PCR (0.5 min at 94° C., 0.5 min at 55° C., 1 min at 70° C., 30 cycles) using primers identified as SEQ ID NO: 33 and SEQ ID NO: 34. The resulting nucleic acid product (SEQ ID NO: 53) was subcloned into pTrcHis2-TOPO® (Invitrogen, Carlsbad Calif.) to generate the plasmid identified as pSW195. The plasmid pSW195 was used to transform E. coli KLP18 to generate the strain identified as KLP18/pSW195. KLP18/pSW195 was grown in LB media at 37° C. with shaking up to OD600 nm=0.4-0.5, at which time IPTG was added to a final concentration of 1 mM, and incubation continued for 2-3 h. Cells were harvested by centrifugation and SDS-PAGE was performed to confirm expression of the perhydrolase at 20-40% of total soluble protein.
Example 9
Cloning and Expression of Perhydrolase from Bacillus licheniformis ATCC® 14580™
Genomic DNA was isolated from Bacillus licheniformis ATCC®14580™ using the PUREGENE® DNA purification system. The perhydrolase gene was amplified from the genomic DNA by PCR (0.5 min at 94° C., 0.5 min at 55° C., 1 min at 70° C., 30 cycles) using primers identified as SEQ ID NO: 31 and SEQ ID NO: 32. The resulting nucleic acid product (SEQ ID NO: 7) was subcloned into pTrcHis2-TOPO® to generate the plasmid identified as pSW191. The plasmid pSW191 was used to transform E. coli KLP18 to generate the strain identified as KLP18/pSW191. KLP18/pSW191 was grown in LB media at 37° C. with shaking up to OD 600nm =0.4-0.5, at which time IPTG was added to a final concentration of 1 mM, and incubation continued for 2-3 h. Cells were harvested by centrifugation and SDS-PAGE was performed to confirm expression of the perhydrolase at 20-40% of total soluble protein.
Example 10
Fermentation of E. coli KLP18 Transformants Expressing Perhydrolase
A fermentor seed culture was prepared by charging a 2-L shake flask with 0.5 L seed medium containing yeast extract (Amberx 695, 5.0 g/L), K 2 HPO 4 (10.0 g/L), KH 2 PO 4 (7.0 g/L), sodium citrate dihydrate (1.0 g/L), (NH 4 ) 2 SO 4 (4.0 g/L), MgSO 4 heptahydrate (1.0 g/L) and ferric ammonium citrate (0.10 g/L). The pH of the medium was adjusted to 6.8 and the medium was sterilized in the flask. Post sterilization additions included glucose (50 wt %, 10.0 mL) and 1 mL ampicillin (25 mg/mL) stock solution. The seed medium was inoculated with a 1-mL culture of E. coli KLP18/pSW189, E. coli KLP18/pSW191, E. coli KLP18/pSW194, E. coli KLP18/pSW195, E. coli KLP18/pSW196, or E. coli KLP18/pSW207 in 20% glycerol, and cultivated at 35° C. and 300 rpm. The seed culture was transferred at ca. 1-2 OD 550 to a 14 L fermentor (Braun) with 8 L of medium at 35° C. containing KH 2 PO 4 (3.50 g/L), FeSO 4 heptahydrate (0.05 g/L), MgSO 4 heptahydrate (2.0 g/L), sodium citrate dihydrate (1.90 g/L), yeast extract (Ambrex 695, 5.0 g/L), Biospumex153K antifoam (0.25 mL/L, Cognis Corporation), NaCl (1.0 g/L), CaCl 2 dihydrate (10 g/L), and NIT trace elements solution (10 mL/L). The trace elements solution contained citric acid monohydrate (10 g/L), MnSO 4 hydrate (2 g/L), NaCl (2 g/L), FeSO 4 heptahydrate (0.5 g/L), ZnSO 4 heptahydrate (0.2 g/L), CuSO 4 pentahydrate (0.02 g/L) and NaMoO 4 dihydrate (0.02 g/L). Post sterilization additions included glucose solution (50% w/w, 80.0 g) and ampicillin (25 mg/mL) stock solution (16.00 mL). Glucose solution (50% w/w) was used for fed batch. Glucose feed was initiated when glucose concentration decreased to 0.5 g/L, starting at 0.31 g feed/min and increasing progressively each hour to 0.36, 0.42, 0.49, 0.57, 0.66, 0.77, 0.90, 1.04, 1.21, 1.41 1.63 g/min respectively; the rate remained constant afterwards. Glucose concentration in the medium was monitored and if the concentration exceeded 0.1 g/L the feed rate was decreased or stopped temporarily. Induction was initiated between OD 550 =56 and OD 550 =80 with addition of 16 mL IPTG (0.5 M) for the various strains. The dissolved oxygen (DO) concentration was controlled at 25% of air saturation. The DO was controlled first by impeller agitation rate (400 to 1400 rpm) and later by aeration rate (2 to 10 slpm). The pH was controlled at 6.8. NH 4 OH (29% w/w) and H 2 SO 4 (20% w/v) were used for pH control. The head pressure was 0.5 bars. The cells were harvested by centrifugation 16 h post IPTG addition.
Example 11
Dependence of Specific Activity on pH for CE-7 Esterases/Perhydrolases
A cell extract of an E. coli transformant expressing perhydrolase from Thermotoga neapolitana (KLP18/pSW196), Thermotoga maritima MSB8 (KLP18/pSW207), Bacillus pumilus PS213 (KLP1S/pSW195), Bacillus subtilis BE1010 (KLP18/pSW189), Bacillus subtilis ATCC® 31954™ (KLP18/pSW194), or Bacillus licheniformis ATCC® 14580™ (KLP18/pSW191) was prepared by passing a suspension of cell paste (20 wt % wet cell weight) in 0.05 M potassium phosphate buffer (pH 7.0) containing dithiothreitol (1 mM) twice through a French press having a working pressure of 16,000 psi (˜110 MPa). The crude extract was then centrifuged at 20,000×g to remove cellular debris, producing a clarified cell extract that was assayed for total soluble protein (Bicinchoninic Acid Kit for Protein Determination, Sigma Aldrich catalog #BCA1-KT). A portion of the clarified Thermotoga maritima MSB8 or Thermotoga neapolitana perhydrolase-containing extract was additionally heated for 20 min at 75° C., followed immediately by cooling in an ice/water bath to 5° C. The resulting mixture was centrifuged to remove precipitated protein, and the supernatant collected and assayed for total soluble protein as before. SDS-PAGE of the heat-treated supernatant indicated that the perhydrolase constituted at least ca. 90% of the total soluble protein present in the supernatant.
Reactions (10 mL total volume) containing triacetin (200 mM) and cell extract supernatant (prepared as described above) were run at 25° C. and at a pH between 4.5 and 10.0, using the buffers and buffer concentrations listed in Table 5. The concentration of extract total protein (with or without heat-treatment to denature and precipitate E. coli -derived protein) was chosen to produce an ca. 50 mM decrease in triacetin concentration over 30 min (typically from 0.025 mg/mL to 0.40 mg/mL of total extract protein, dependent on the perhydrolase). A control reaction for each reaction condition was run to determine the concentration of triacetin hydrolyzed in the absence of added extract protein. Samples (100 μL) were removed at predetermined times and immediately added to 297 μL of dd H 2 O and 3 μL of 6N HCL. The resulting solution was mixed, then filtered using a 30,000 NMWL filter (Millipore) using a microcentrifuge for 2 min at 12,000 rpm. An aliquot of the filtrate (100 μL) was added to 150 μL of 0.417 mM N,N-diethyl meta-toluamide (external standard) in acetonitrile, and the resulting solution analyzed for triacetin by HPLC using a Supelco Discovery C8 column (25 cm×4.0 mm, 5 um; Supelco #59353-U40) and an isocratic mobile phase of 40% acetonitrile/60% distilled water at a flow rate of 1 mL/min. Triacetin was measured by UV detection at 225 nm. The dependence of specific activity on pH for each perhydrolase is listed in Table 6.





TABLE 5



Buffer and buffer concentration employed for

determination of dependence of CE-7 esterase/perhydrolase

specific activity on pH.





pH
Buffer
Buffer Concentration (M)







5.0
sodium acetate
0.15

5.5
sodium acetate
0.15

6.0
sodium citrate
0.15

6.5
sodium citrate
0.15

7.0
potassium phosphate
0.15

7.5
potassium phosphate
0.15

8.0
potassium phosphate
0.20

8.5
Tris(hydroxymethyl)aminomethane
0.20

9.0
Tris(hydroxymethyl)aminomethane
0.20

9.5
glycine
0.20

10.0
glycine
0.20









































TABLE 6



Dependence of specific activity (mmol triacetin/min/mg total extract

protein) on pH for hydrolysis of triacetin by perhydrolases expressed

in E. coli KLP18 transformants using 200 mM triacetin and 0.050-0.40

mg/mL of cell extract total protein (ND = not determined).





specific activity (mmol triacetin/min/mg total extract protein)















Bacillus






Thermotoga



Bacillus


subtilis




Thermotoga


maritima


Bacillus


subtilis

ATCC ®

Bacillus.


pH

neapolitana

MSB8

pumilus

BE1010
31954 ™

licheniformis.












10.0
0
ND
ND
ND
0
ND

9.5
12.0
21.6
71.1
ND
193
ND

9.0
12.5
57.1
80.4
ND
239
ND

8.5
11.3
38.8
72.4
ND
217
ND

8.0
5.8
28.7
53.9
ND
221
ND

7.5
5.3
19.8
33.7
61.0
205
62.4

7.0
3.3
16.0
30.5
37.7
120
56.3

6.5
1.7
10.3
11.6
18.6
78.0
23.8

6.0
0.4
4.3
4.2
7.4
24.0
12.3

5.5
0
1.4
3.5
0
17.6
4.7

5.0

ND
1.8

7.6
ND

4.5


ND

0.5













































Example 12
Control of Peracetic Acid Production by Thermotoga neapolitana Perhydrolase Using Buffer Concentration
A cell extract of an E. coli transformant expressing perhydrolase from Thermotoga neapolitana (KLP18/pSW196) was prepared by passing a suspension of cell paste (20 wt % wet cell weight) in 0.05 M potassium phosphate buffer (pH 7.0) containing dithiothreitol (1 mM) twice through a French press having a working pressure of 16,000 psi (˜110 MPa). The crude extract was then centrifuged at 20,000×g to remove cellular debris, producing a clarified cell extract that was assayed for total soluble protein (Bicinchoninic Acid Kit for Protein Determination, Sigma Aldrich catalog #BCA1-KT). The clarified extract was heated for 20 min at 75° C., followed immediately by cooling in an ice/water bath. The resulting mixture was centrifuged to remove precipitated protein, and the supernatant collected and assayed for total soluble protein as before. SDS-PAGE of the supernatant indicated that the perhydrolase was at least 90% pure. The supernatant was frozen in dry ice and stored at −80° C.
Reactions (10 mL total volume) containing triacetin, hydrogen peroxide and heat-treated, centrifuged cell extract supernatant (prepared as described above) were run at 25° C. using sodium bicarbonate buffer concentrations listed in Tables 7 and 8. A control reaction for each reaction condition was run to determine the concentration of peracetic acid produced by chemical perhydrolysis of triacetin by hydrogen peroxide in the absence of added extract protein.
Determination of the concentration of peracetic acid in the reaction mixtures was performed according to the method described by Karst et al., supra. Aliquots (0.040 mL) of the reaction mixture were removed at predetermined times and mixed with 0.960 mL of 5 mM phosphoric acid in water; adjustment of the pH of the diluted sample to less than pH 4 immediately terminated the reaction. The resulting solution was filtered using an ULTRAFREE® MC-filter unit (30,000 Normal Molecular Weight Limit (NMWL), Millipore cat #UFC3LKT 00) by centrifugation for 2 min at 12,000 rpm. An aliquot (0.100 mL) of the resulting filtrate was transferred to L5-mL screw cap HPLC vial (Agilent Technologies, Palo Alto, Calif.; #5182-0715) containing 0.300 mL of deionized water, then 0.100 mL of 20 mM MTS (methyl-p-tolyl-sulfide) in acetonitrile was added, the vials capped, and the contents briefly mixed prior to a 10 min incubation at ca. 25° C. in the absence of light. To each vial was then added 0.400 mL of acetonitrile and 0.100 mL of a solution of triphenylphosphine (TPP, 40 mM) in acetonitrile, the vials re-capped, and the resulting solution mixed and incubated at ca. 25° C. for 30 min in the absence of light. To each vial was then added 0.100 mL of 10 mM N,N-diethyl-m-toluamide (DEET; HPLC external standard) and the resulting solution analyzed by HPLC as described below.
HPLC Method:
Supelco Discovery C8 column (10-cm×4.0-mm, 5 μm) (cat. #569422-U) w/precolumn Supelco Supelguard Discovery C8 (Sigma-Aldrich; cat #59590-U); 10 microliter injection volume; gradient method with CH 3 CN (Sigma-Aldrich; #270717) and deionized water at 1.0 mL/min and ambient temperature:
Time (min:sec) (% CH 3 CN) 0:00 40 3:00 40 3:10 100 4:00 100 4:10 40 7:00 (stop) 40
The peracetic acid concentrations produced in 1 min, 5 min and 30 min when using either 250 mM or 100 mM hydrogen peroxide are listed in Table 7 and Table 8, respectively.






TABLE 7



Dependence of peracetic acid (PAA) concentration on concentration

of bicarbonate buffer when using 100 mM triacetin, 250 mM hydrogen peroxide

and 50 μg/mL of E. coli KLP18/pSW196 heat-treated extract total

protein containing Thermotoga neapolitana perhydrolase.











heated extract
NaHCO 3

PAA

PAA

PAA


total protein
buffer
initial
(ppm),
pH,
(ppm),
pH,
(ppm),
pH,

(μg protein/mL)
(mM)
pH
1 min
1 min
5 min
5 min
30 min
30 min













0
25
8.1
139
8.0
385
7.5
610
7.2

50
25
8.1
1037
6.8
2655
6.0
3503
5.8

0
10
7.5
88
7.5
206
7.5
453
7.0

50
10
7.0
1042
7.0
2334
5.5
2384
5.0

0
5.0
6.5
84
6.5
163
6.5
296
6.0

50
5.0
6.5
866
6.5
1894
5.5
1931
5.0

0
2.5
6.5
48
5.5
129
5.5
210
5.5

50
2.5
6.5
718
5.5
1242
5.0
1179
5.0

0
1.0
6.0
15
6.0
115
6.0
194
5.5

50
1.0
6.0
511
5.0
610
5.0
608
5.0

0
0
5.0
41
5.0
63
5.0
79
5.0

50
0
5.0
161
5.0
152
5.0
180
5.0













































TABLE 8



Dependence of peracetic acid (PAA) concentration on concentration

of bicarbonate buffer when using 100 mM triacetin, 100 mM hydrogen peroxide

and 50 μg/mL of E. coli KLP18/pSW196 heat-treated extract total

protein containing Thermotoga neapolitana perhydrolase.











heated extract
NaHCO 3

PAA

PAA

PAA


total protein
buffer
initial
(ppm),
pH,
(ppm),
pH,
(ppm),
pH,

(μg protein/mL)
(mM)
pH
1 min
1 min
5 min
5 min
30 min
30 min













0
25
8.1
74
8.0
220
7.8
383
7.5

50
25
8.1
497
7.5
1319
6.5
2095
6.0

0
10
8.1
55
7.5
122
7.0
226
7.0

50
10
8.1
418
6.2
1035
6.0
1633
5.3

0
5.0
6.5
36
6.5
119
6.5
126
6.0

50
5.0
6.5
377
6.0
955
5.5
989
5.0

0
2.5
6.5
20
6.3
33
6.0
73
6.0

50
2.5
6.5
291
5.5
510
5.3
488
5.0

0
1.0
6.0
2
6.0
15
5.8
103
5.5

50
1.0
6.0
167
5.0
152
5.0
176
5.0

0
0
5.0
0
5.0
15
5.0
31
5.0

50
0
5.0
0
5.0
29
5.0
11
5.0








































Example 13
Control of Peracetic Acid Production by Thermotoga maritima MSB8 Perhydrolase Using Buffer Concentration
A cell extract of a transformant expressing perhydrolase from Thermotoga maritima MSB8 (KLP18/pSW207) was prepared by passing a suspension of cell paste (20 wt % wet cell weight) in 0.05 M potassium phosphate buffer (pH 7.0) containing dithiothreitol (1 mM) twice through a French press having a working pressure of 16,000 psi (˜110 MPa). The crude extract was then centrifuged at 20,000×g to remove cellular debris, producing a clarified cell extract that was assayed for total soluble protein (Bicinchoninic Acid Kit for Protein Determination, Sigma Aldrich catalog #BCA1-KT). The clarified extract was heated for 20 min at 75° C., followed immediately by cooling in an ice/water bath. The resulting mixture was centrifuged to remove precipitated protein, and the supernatant collected and assayed for total soluble protein as before. SDS-PAGE of the supernatant indicated that the perhydrolase was at least 85-90% pure. The supernatant was frozen in dry ice and stored at −80° C.
Reactions (2 mL total volume) containing triacetin, hydrogen peroxide and heat-treated, centrifuged cell extract supernatant (prepared as described above) were run at 25° C. using sodium bicarbonate buffer concentrations listed in Tables 9 and 10. A control reaction for each reaction condition was run to determine the concentration of peracetic acid produced by chemical perhydrolysis of triacetin by hydrogen peroxide in the absence of added extract protein. Determination of the concentration of peracetic acid in the reaction mixtures was performed according to the method described by Karst et al., supra. The peracetic acid concentrations produced in 1 min, 5 min and 30 min using either 250 mM or 100 mM hydrogen peroxide are listed in Table 9 and Table 10.





TABLE 9



Dependence of peracetic acid (PAA) concentration on concentrations of

bicarbonate buffer when using 100 mM triacetin, 250 mM hydrogen peroxide

and 50 μg/mL of E. coli KLP18/pSW207 heat-treated extract total protein

containing Thermotoga maritima MSB8 perhydrolase.











heated extract
NaHCO 3

PAA

PAA

PAA


total protein
buffer
initial
(ppm),
pH,
(ppm),
pH,
(ppm),
pH,

(μg protein/mL)
(mM)
pH
1 min
1 min
5 min
5 min
30 min
30 min













0
25
8.1
144
8.0
324
8.0
759
7.2

50
25
8.1
848
7.0
2342
6.5
3251
6.0

0
10
7.5
182
7.0
194
7.0
454
6.5

50
10
7.0
804
6.3
1951
5.5
2698
5.0

0
5.0
6.5
84
6.5
163
6.5
296
6.0

50
5.0
6.5
735
6.0
1825
5.7
2222
5.0

0
2.5
6.5
48
5.5
129
5.5
210
5.5

50
2.5
6.5
817
5.5
1758
5.3
1748
5.0

0
1.0
6.0
15
6.0
115
6.0
194
5.5

50
1.0
6.0
690
5.0
980
5.0
981
5.0

0
0
5.0
0
5.0
75
5.0
63
5.0

50
0
5.0
233
5.0
290
5.0
289
5.0













































TABLE 10



Dependence of peracetic acid (PAA) concentration on concentrations of

bicarbonate buffer when using 100 mM triacetin, 100 mM hydrogen peroxide

and 50 μg/mL of E. coli KLP18/pSW207 heat-treated extract total protein

containing Thermotoga maritima MSB8 perhydrolase.











heated extract
NaHCO 3

PAA

PAA

PAA


total protein,
buffer
initial
(ppm),
pH,
(ppm),
pH,
(ppm),
pH,

(μg protein/mL
(mM)
pH
1 min
1 min
5 min
5 min
30 min
30 min













0
25
8.1
95
8.0
223
8.0
456
7.5

50
25
8.1
465
7.5
1369
6.8
2217
6.0

0
10
8.1
73
7.5
138
7.5
222
7.0

50
10
8.1
407
6.5
1075
6.0
1763
5.3

0
5.0
6.5
41
6.5
83
6.5
174
6.0

50
5.0
6.5
330
6.0
972
5.7
1323
5.0

0
2.5
6.5
20
6.3
33
6.0
73
6.0

50
2.5
6.5
319
5.7
755
5.3
710
5.0

0
1.0
6.0
2
6.0
15
5.8
103
5.5

50
1.0
6.0
238
5.0
388
5.0
361
5.0

0
0
5.0
12
5.0
16
5.0
31
5.0

50
0
5.0
125
5.0
121
5.0
105
5.0








































Example 14
Control of Peracetic Acid Production by Thermotoga maritima MSB8 Perhydrolase by Selection of Buffer, Reactant and Perhydrolase Concentrations
Reactions (10 mL total volume) containing triacetin (100 mM), hydrogen peroxide (100 mM or 250 mM) and heat-treated, centrifuged cell extract supernatant (35 to 100 μg total heat-treated extract protein/mL, prepared as described in Example 13) prepared from an E. coli transformant expressing perhydrolase from Thermotoga maritima MSB8 (KLP18/pSW207) in sodium citrate (50 mM, pH 6.5) buffer, or in sodium bicarbonate buffer (1 mM to 5 mM, initial pH as indicated in Table 12), or in water without added buffer were run at 25° C. A control reaction for each reaction condition was run to determine the concentration of peracetic acid produced by chemical perhydrolysis of triacetin by hydrogen peroxide in the absence of added extract protein. Determination of the concentration of peracetic acid in the reaction mixtures was performed according to the method described by Karst et al., supra. The peracetic acid concentration produced at predetermined reaction times is listed in Table 11, and the corresponding reaction pH at each reaction time is listed in Table 12.





TABLE 11



Dependence of peracetic acid (PAA) concentration over time on buffer, perhydrolase

and hydrogen peroxide concentrations when reacting triacetin (100 mM) and

hydrogen peroxide (100 mM or 250 mM) in the presence or absence of perhydrolase

from E. coli KLP18/pSW207 heat-treated extract total protein containing

Thermotoga maritima MSB8 perhydrolase.












total
PAA
PAA
PAA
PAA
PAA


H 2 O 2
protein
(ppm),
(ppm),
(ppm),
(ppm),
(ppm),

buffer, conc.
(mM)
(μg/mL)
1 min
5 min
30 min
2 h
18 h












citrate, 50 mM
100
0
155
0
0
119
522

citrate, 50 mM
100
50
409
892
2001
2254
1937

bicarbonate, 5 mM
100
0
64
115
269
369
419

bicarbonate, 5 mM
100
50
410
1088
1496
1423
1419

bicarbonate, 1 mM
250
0
0
22
229
280
258

bicarbonate, 1 mM
250
50
624
1060
1090
1063
1021

bicarbonate, 1 mM
250
0
18
105
236
275
149

bicarbonate, 1 mM
250
35
467
1047
1041
1014
917

bicarbonate, 2.5 mM
100
0
54
38
156
293
346

bicarbonate, 2.5 mM
100
50
256
722
976
887
855

bicarbonate, 1 mM
100
0
28
78
141
204
164

bicarbonate, 1 mM
100
75
434
494
608
673
576

bicarbonate, 1 mM
100
100
449
667
643
703
613

water (no buffer)
250
0
13
71
71
33
45

water (no buffer)
250
75
512
535
533
472
448

water (no buffer)
250
100
576
668
654
618
543


















































TABLE 12



Dependence of reaction pH over time on buffer, perhydrolase and hydrogen peroxide

concentrations when reacting triacetin (100 mM) and hydrogen peroxide (100 mM or

250 mM) in the presence or absence of perhydrolase from E. coli KLP18/

pSW207 heat-treated extract total protein containing Thermotoga maritima

MSB8 perhydrolase (from reactions listed in Table 11).













total








H 2 O 2
protein
initial
pH,
pH,
pH,
pH,
pH,

buffer, conc.
(mM)
(μg/mL)
pH
1 min
5 min
30 min
2 h
18 h













citrate, 50 mM
100
0
6.5
6.5
6.5
6.5
6.5
6.5

citrate, 50 mM
100
50
6.5
6.5
6.5
6.2
6.0
6.0

bicarbonate, 5 mM
100
0
6.5
6.5
6.5
6.2
6.0
5.0

bicarbonate, 5 mM
100
50
6.5
6.0
5.5
5.0
5.0
5.0

bicarbonate, 1 mM
250
0
6.0
6.0
6.0
5.5
5.0
5.0

bicarbonate, 1 mM
250
50
6.0
5.0
5.0
5.0
5.0
5.0

bicarbonate, 1 mM
250
0
6.0
6.0
6.0
5.5
5.0
5.0

bicarbonate, 1 mM
250
35
6.0
5.5
5.0
5.0
5.0
5.0

bicarbonate, 2.5 mM
100
0
6.5
6.5
6.5
6.0
5.5
5.0

bicarbonate, 2.5 mM
100
50
6.5
5.7
5.0
5.0
5.0
5.0

bicarbonate, 1 mM
100
0
6.0
6.0
6.0
5.0
5.0
4.5

bicarbonate, 1 mM
100
75
6.0
5.0
5.0
5.0
5.0
4.5

bicarbonate, 1 mM
100
100
6.0
5.0
5.0
5.0
5.0
4.5

no added buffer
250
0
5.0
5.0
5.0
5.0
5.0
4.5

no added buffer
250
75
5.0
5.0
5.0
5.0
5.0
4.5

no added buffer
250
100
5.0
5.0
5.0
5.0
5.0
4.5













































Example 15
Control of Peracetic Acid Production by Perhydrolase Using Initial Reaction pH
A cell extract of a transformant expressing perhydrolase from Bacillus pumilus PS213 (KLP18/pSW195), Thermotoga maritima MSB8 (KLP18/pSW207), Thermotoga neapolitana (KLP18/pSW196), or Bacillus subtilis ATCC® 31954™ (KLP18/pSW194) was prepared by passing a suspension of cell paste (20 wt % wet cell weight) in 0.05 M potassium phosphate buffer (pH 7.0) containing dithiothreitol (1 mM) twice through a French press having a working pressure of 16,000 psi (˜110 MPa). The crude extract was then centrifuged at 20,000×g to remove cellular debris, producing a clarified cell extract that was assayed for total soluble protein (Bicinchoninic Acid Kit for Protein Determination, Sigma Aldrich catalog #BCA1-KT). The supernatant was frozen in dry ice and stored at −80° C.
Reactions (10 mL total volume) containing triacetin, hydrogen peroxide and centrifuged cell extract supernatant (prepared as described above) in 50 mM sodium citrate buffer (initial pH 7.2 or 6.5) were run at 25° C. A control reaction for each reaction condition was run to determine the concentration of peracetic acid produced by chemical perhydrolysis of triacetin by hydrogen peroxide in the absence of added extract protein (data not shown). Determination of the concentration of peracetic acid in the reaction mixtures was performed according to the method described by Karst et al., supra. The peracetic acid concentrations produced in 1 min, 5 min and 30 min are listed in Table 13.





TABLE 13



Dependence of peracetic acid (PAA) concentration on initial reaction pH

in sodium citrate buffer (50 mM, initial pH of 7.2 or 6.5) at 25° C. using

0.050 mg/mL of extract total protein from E. coli KLP18/pSW195

( Bacillus pumilus PS213 perhydrolase), E. coli

KLP18/pSW207 ( Thermotoga maritima MSB8 perhydrolase), E. coli

KLP18/pSW196 ( Thermotoga neapolitana perhydrolase), or E. coli

KLP18/pSW194 ( Bacillus subtilis ATCC ® 31954 ™ perhydrolase).













PAA,
PAA,
PAA,


initial
triacetin
H 2 O 2
1 min
5 min
30 min

perhydrolase
pH
(mM)
(mM)
(ppm)
(ppm)
(ppm)











B. pumilus PS213
7.2
100
250
465
1170
2525

B. pumilus PS213
6.5
100
250
281
652
1984

B. pumilus PS213
7.2
100
100
160
322
1010

B. pumilus PS213
6.5
100
100
170
310
830


T. neapolitana

7.2
100
250
1790
2860
3820


T. neapolitana

6.5
100
250
434
1260
2016


T. neapolitana

7.2
100
100
798
1748
2500


T. neapolitana

6.5
100
100
221
607
1925

T. maritima MSB8
7.2
100
250
635
1725
3565

T. maritima MSB8
6.5
100
250
95
742
2446

T. maritima MSB8
7.2
100
100
210
610
1995

T. maritima MSB8
6.5
100
100
53
279
1540

B. subtilis ATCC
7.2
100
250
2430
2820
4400

31954

B. subtilis ATCC
6.5
100
250
1725
2570
3712

31954

B. subtilis ATCC
7.2
100
100
1040
1240
2395

31954

B. subtilis ATCC
6.5
100
100
691
1286
1880

31954