Control of enzymatic peracid generation
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. 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.
2. The process of claim 1 , wherein the at least one buffer is present in a concentration in a range from about 0.01 mM to about 200 mM.
3. The process of claim 1 , wherein the reaction products reduce the reaction mixture pH to about 5.0 within about 1 minute to about 10 minutes of combining the reaction components.
4. The process of claim 1 , wherein the target concentration of peroxycarboxylic acid is from about 200 parts per million to about 2500 parts per million.
5. The process of claim 4 , wherein the target concentration of peroxycarboxylic acid is from about 400 parts per million to about 1200 parts per million.
6. The process of claim 5 , wherein the target concentration of peroxycarboxylic acid is from about 400 parts per million to about 600 parts per million.
7. The process of claim 1 , wherein the target concentration of peroxycarboxylic acid is achieved within about 1 to about 10 minutes of mixing the reaction components.
8. The process of claim 1 , wherein the target concentration of peroxycarboxylic acid is achieved within at least about 5 minutes of mixing the reaction components.
9. The process of claim 8 , wherein the target concentration of peroxycarboxylic acid is achieved within about 1 minute of mixing the reaction components.
10. The process of claim 1 , wherein the concentration of peroxycarboxylic acid changes by less than about 20% of said target concentration once the target concentration of peroxycarboxylic acid is achieved.
11. The process of claim 1 , wherein the buffer has a pKa from about 8.0 to about 6.0.
12. The process of claim 1 , wherein the initial pH of the initial reaction mixture is selected from the group consisting of 6.5, 7.2, 7.5, 8.1, and 8.5.
13. The process of claim 1 , wherein enzyme catalyst having perhydrolysis activity is derived from Thermotoga neapolitana.
14. The process of claim 1 , wherein enzyme catalyst having perhydrolysis activity is derived from Thermotoga maritima MSB8.
15. The process of claim 1 , wherein the reduction in pH reduces perhydrolase activity by about 80% or more in 10 minutes or less after combining the reaction components.
16. The process of claim 1 wherein the enzyme catalyst is in the form of a microbial cell, a permeabilized microbial cell, a microbial cell extract, a partially purified enzyme, a purified enzyme, or an immobilized form of a partially purified or purified enzyme.
17. The process of claim 1 wherein the peroxycarboxylic acid is selected from the group consisting of peracetic acid, perpropionic acid, perbutyric acid, perlactic acid, perglycolic acid, permethoxyacetic acid, per-β-hydroxybutyric acid, and mixtures thereof.
18. The process of claim 1 wherein the enzyme catalyst lacks catalase activity.