Patent Application
20130158115
The invention relates to the field of peroxycarboxylic acid biosynthesis and enzyme catalysis. An enzyme catalyst comprising a variant enzyme having perhydrolytic activity is provided having an increase in specific activity in the presence of an anionic surfactant commonly used in laundry care formulations. Methods of using the present enzyme catalyst to produce peroxycarboxylic acids are also provided.
Peroxycarboxylic acid compositions can be effective antimicrobial agents. Methods of using peroxycarboxylic acids to clean, disinfect, and/or sanitize hard surfaces, textiles, 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 No. 2003-0026846; and U.S. Pat. No. 5,683,724). Peroxycarboxylic acids have also been used in various bleaching applications including, but not limited to, wood pulp bleaching/delignification and laundry care applications (European Patent 1040222B1; U.S. Pat. No. 5,552,018; U.S. Pat. No. 3,974,082; U.S. Pat. No. 5,296,161; and U.S. Pat. No. 5,364,554). The desired efficacious concentration of peroxycarboxylic acid may vary according to the product application (for example, ca. 500 ppm to 1000 ppm for medical instrument disinfection, ca. 30 ppm to 80 ppm for laundry bleaching or disinfection applications) in 1 min to 5 min reaction time at neutral pH.
Enzymes structurally classified as members of family 7 of the carbohydrate esterases (CE-7) have been employed as perhydrolases to catalyze the reaction of hydrogen peroxide (or alternative peroxide reagent) with alkyl esters of carboxylic acids in water at a basic to acidic pH range (from ca. pH 11.5 to ca. pH 5) to produce an efficacious concentration of a peroxycarboxylic acid for such applications as disinfection (such as medical instruments, hard surfaces, textiles), bleaching (such as wood pulp or paper pulp processing/delignification, textile bleaching and laundry care applications), and other laundry care applications such as destaining, deodorizing, and sanitization (U.S. Pat. Nos. 7,964,378; 7,951,566; and 7,723,083 and Published U.S. Patent Application Nos. 2008-0176299, and 2010-0041752 to DiCosimo et al.). The CE-7 enzymes have been found to have high specific activity for perhydrolysis of esters, particularly acetyl esters of alcohols, diols, glycerols and phenols, and acetyl esters of mono-, di- and polysaccharides.
Published U.S. Patent Application No. 2010-0087529 to DiCosimo et al. describes several variant CE-7 perhydrolases derived from several Thermotoga sp. having higher perhydrolytic specific activity and/or improved selectivity for perhydrolysis when used to prepare peroxycarboxylic acid from carboxylic acid esters. Two of the variants described in Published U.S. Patent Application No. 2010-0087529, Thermotoga maritima C277S and Thermotoga maritima C277T, exhibited a significant improvement in specific activity relative to the T. maritima wild-type enzyme.
Thermotoga maritima variants having higher peracid stability were also reported by DiCosimo et al. in U.S. Pat. Nos. 7,927,854; 7,923,233; 7,932,072; 7,910,347; and 7,960,528. Each variant was characterized as having an increased peracetic acid formation to peracetic acid hydrolysis ratio (PAAF:PAAH) when compared to the T. maritima wild-type perhydrolase or the T. maritima C277S variant perhydrolase.
Several variants of the Thermotoga maritima C277S perhydrolase have been identified which have higher specific activity for the perhydrolysis of esters when compared to the specific activity of the Thermotoga maritima C277S (U.S. Patent Application Nos. 2011-0236335, 2011-0236336, 2011-0236337, 2011-0236338, and 2011-0236339 to DiCosimo et al.). However, there remains a need to identify additional variants having an increase in perhydrolytic specific activity.
Perhydrolytic enzymes may be used in laundry care applications. However, laundry care formulations may comprise one or more anionic surfactants that may adversely impact the specific activity of the perhydrolytic enzyme. As such, a need exists to identify perhydrolytic enzymes having improved specific activity in the presence of one or more anionic surfactants, such as alkyl benzene sulphonic acids, alkyl sulphonic acids or aryl sulphonic acids, at concentrations representative of laundry care conditions.
The problem to be solved is to provide an enzyme catalyst comprising a CE-7 perhydrolase having higher specific activity in the presence of an anionic surfactant when compared to the specific activity of the Thermotoga maritima C277T perhydrolase under the same reaction conditions.
Nucleic acid molecules encoding the Thermotoga maritima acetyl xylan esterase variant C277T were mutated to create libraries of variant enzymes having perhydrolytic activity. Several perhydrolase variants were identified having an improvement in specific activity in the presence of an anionic surfactant when compared to the parent enzyme from which they were derived (i.e., the Thermotoga maritima C277T perhydrolase) under the same reaction conditions.
In one embodiment, an isolated nucleic acid molecule encoding a polypeptide having perhydrolytic activity is provided selected from the group consisting of:
In other embodiments, a vector, a recombinant DNA construct, and a recombinant host cell comprising the present polynucleotide are also provided.
In another embodiment, a method for transforming a cell is provided comprising transforming a cell with the above nucleic acid molecule.
In another embodiment, an isolated polypeptide having perhydrolysis activity is provided comprising the amino acid sequence of SEQ ID NO: 4.
In one embodiment, the variant polypeptide having perhydrolytic activity is characterized by a relative increase in specific activity in the presence of one or more anionic surfactants (as determined by an increased amount of peroxycarboxylic acid produced) when compared to the specific activity of the Thermotoga maritima C277T variant (Published U.S. Patent Application No. 2010-0087529 to DiCosimo et al.) under identical reaction conditions. In a preferred aspect, the relative increase in activity is measured under reaction conditions that include the presence of an anionic surfactant at a concentration representative of that used in laundry conditions (for example, in the presence of about 2 mg/mL to 6 mg/mL surfactant).
In another embodiment, a process for producing a peroxycarboxylic acid is also provided comprising:
[X]mR5
In another embodiment, a process is provided further comprising a step (d) wherein the peroxycarboxylic acid produced in step (b) or step (c) is contacted with a hard surface, an article of clothing or an inanimate object whereby the hard surface, article of clothing or inanimate object is disinfected, sanitized, bleached, destained, deodorized or any combination thereof.
In another embodiment, a composition is provided comprising:
[X]mR5
The present process produces the desired peroxycarboxylic acid upon combining the reaction components. The reaction components may remain separated until use.
In a further aspect, a peroxycarboxylic acid generation and delivery system is provided comprising:
[X]mR5
In a further embodiment, a laundry care composition is provided comprising a polypeptide comprising the amino acid sequence of SEQ ID NO: 4.
In a further embodiment, a personal care composition is provided comprising a polypeptide comprising the amino acid sequence of SEQ ID NO: 4.
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 (2009) 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 codon-optimized coding region encoding the wild-type Thermotoga maritima acetyl xylan esterase having perhydrolytic activity.
SEQ ID NO: 2 is the amino acid sequence of the wild-type Thermotoga maritima acetyl xylan esterase having perhydrolytic activity.
SEQ ID NO: 3 is the amino acid sequence of the C277T variant acetyl xylan esterase having perhydrolytic activity (Published U.S. Patent Application No. 2010-0087529 to DiCosimo et al.).
SEQ ID NO: 4 is the amino acid sequence of the Pro-007 (R15E) variant acetyl xylan esterase.
SEQ ID NO: 5 is the amino acid sequence of the Pro-050 (K13S) variant acetyl xylan esterase.
SEQ ID NO: 6 is the amino acid sequence of the Pro-053 (R218S) variant acetyl xylan esterase.
SEQ ID NO: 7 is the amino acid sequence of the Pro-063 (K316A/K319A/K320A) variant acetyl xylan esterase.
SEQ ID NO: 8 is the nucleic acid sequence encoding the Pro-007 (R15E) variant acetyl xylan esterase.
SEQ ID NO: 9 is the nucleic acid sequence encoding the Pro-050 (K13S) variant acetyl xylan esterase.
SEQ ID NO: 10 is the nucleic acid sequence encoding the Pro-053 (R218S) variant acetyl xylan esterase.
SEQ ID NO: 11 is the nucleic acid sequence encoding the Pro-063 (K316A/K319A/K320A) variant acetyl xylan esterase.
A nucleic acid molecule encoding the Thermotoga maritima C277T variant acetyl xylan esterase was mutated to create a library of variant perhydrolases. In particular, select positively charged, solvent accessible residues were selected and changed to negatively charged or neutral amino acids in an attempt to lessen the interaction between the perhydrolytic enzyme and a model anionic surfactant. Several perhydrolase variants were identified from the library exhibiting an increase in specific activity in the presence of anionic surfactant when compared to the specific activity of the Thermotoga maritima C277T perhydrolase having amino acid sequence SEQ ID NO: 3.
Compositions and methods are provided comprising the variant perhydrolase enzyme having amino acid sequence SEQ ID NO: 4.
In this disclosure, a number of terms and abbreviations are used. The following definitions apply unless specifically stated otherwise.
As used herein, the articles “a”, “an”, and “the” preceding an element or component of the invention are intended to be nonrestrictive regarding the number of instances (i.e., occurrences) of the element or component. Therefore “a”, “an” and “the” should be read to include one or at least one, and the singular word form of the element or component also includes the plural unless the number is obviously meant to be singular.
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.
Where present, all ranges are inclusive and combinable. For example, when a range of “1 to 5” is recited, the recited range should be construed as including ranges “1 to 4”, “1 to 3”, “1-2”, “1-2 & 4-5”, “1-3 & 5”, and the like.
As used herein, the term “multi-component system” will refer to a system of enzymatically generating peroxycarboxylic acid wherein the components remain separated until use. As such, the multi-component system will include at least one first component that remains separated from at least one second component. The first and second components are separated in different compartments until use (i.e., using first and second compartments). The design of the multi-component systems will often depend on the physical form of the components to be combined and are described in more detail below.
As used herein, the term “peroxycarboxylic acid” is synonymous with peracid, peroxyacid, 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 “acylated sugar” and “acylated saccharide” refer to mono-, di- and polysaccharides comprising at least one acyl group, where the acyl group is selected from the group consisting of straight chain aliphatic carboxylates having a chain length from C2 to C8. Examples include, but are not limited to, glucose pentaacetate, galactose pentaacetate, sucrose octaacetate, sorbitol hexaacetate, tetraacetylxylofuranose, α-D-glucopyranose pentaacetate, α-D-mannopyranose pentaacetate, 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 one 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 term “aromatic” refers to an organic compound or moiety characterized by increased chemical stability resulting from the delocalization of electrons in a ring system containing usually multiple conjugated double bonds. Planar monocyclic conjugated rings having delocalized electrons should be aromatic if they have (4n+2) π electrons. Examples of aromatic compounds may include derivatives of benzene (such as 2-, 3- or 4-acetoxybenzoic acid). In one embodiment, the ester substrate may be 4-acetoxybenzoic acid.
As used herein, the term “heterocyclic” refers to an organic compound or moiety with a ring structure having one or more atoms other than carbon in at least one of its rings.
As used herein, the term “heteroaromatic” refers to an organic compound or moiety with a ring structure that is both heterocyclic and aromatic, wherein the ring comprises at least one of the heteroatoms oxygen, nitrogen, or sulfur. Examples of heteroaromatic moieties may include pyridine, pyrrole, furan, and thiophene moieties.
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 term “alkyl benzene sulphonic acid” refers to an anionic surfactant used in laundry care formulations, such as dodecyl benzene sulphonic acid having CAS #27176-87-0, and was used as a representative anionic surfactant to screen for perhydrolytic enzymes having improved specific activity relative to the specific activity of the C277T Thermotoga maritima perhydrolase (SEQ ID NO: 3) in the presence of the anionic surfactant. Examples of other anionic surfactants used in the laundry care and personal care industry may include, but are not limited to, alkyl sulphonic acid, aryl sulphonic acid, and alcohol ethoxylated sulphonic acid (see: J. J. Scheibel, J. Surfactants and Detergents, (2004) 7:319-327), at concentrations of from about 1 g/L to about 20 g/L.
As used herein, the terms “suitable enzymatic reaction formulation”, “components suitable for generation of a peroxycarboxylic acid”, “suitable reaction components”, “reaction components”, “reaction formulation”, and “suitable aqueous reaction formulation” refer to the materials and water in which the reactants and the enzyme catalyst comprising the present variant polypeptide having perhydrolytic activity come into contact to form the desired peroxycarboxylic acid. The components of the reaction formulation are provided herein and those skilled in the art appreciate the range of component variations suitable for this process. In one embodiment, the enzymatic reaction formulation produces peroxycarboxylic acid in situ upon combining the reaction components. As such, the reaction components may be provided as a multi-component 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 multi-chamber dispenser bottles or two-phase systems (U.S. Patent Application Publication 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 080715661; U.S. Patent Application Publication No. 2005-0008526; and PCT Publication No. WO 00/61713A1) such as found in some bleaching applications wherein the desired bleaching agent is produced upon mixing the reactive fluids. Multi-component formulations and multi-component generation systems to enzymatically produce peroxycarboxylic acids from carboxylic acid esters are described by DiCosimo et al. in Published U.S Patent Application Nos. 2010-0086510 and 2010-0086621, respectively. Other forms of multi-component systems used to generate peroxycarboxylic acid may include, but are not limited to, those designed for one or more solid components or combinations of solid-liquid components, such as powders used in many commercially available bleaching compositions (e.g., U.S. Pat. No. 5,116,575), multi-layered tablets (e.g., U.S. Pat. No. 6,210,639), water dissolvable packets having multiple compartments (e.g., U.S. Pat. No. 6,995,125) and solid agglomerates that react upon the addition of water (e.g., U.S. Pat. No. 6,319,888).
As used herein, the term “substrate” or “carboxylic acid ester substrate” will refer to the reaction components enzymatically perhydrolyzed using the present enzyme catalyst in the presence of a suitable source of peroxygen, such as hydrogen peroxide. In one embodiment, the substrate comprises at least one ester group capable of being enzymatically perhydrolyzed using the enzyme catalyst, whereby a peroxycarboxylic acid is produced.
As used herein, the term “perhydrolysis” is defined as the reaction of a selected substrate with a source of hydrogen peroxide to form a peroxycarboxylic acid. Typically, inorganic peroxide is reacted with the selected substrate in the presence of a catalyst to produce the peroxycarboxylic acid. As used herein, the term “chemical perhydrolysis” includes perhydrolysis reactions in which a substrate (such as a peroxycarboxylic acid precursor) is combined with a source of hydrogen peroxide wherein peroxycarboxylic acid is formed in the absence of an enzyme catalyst. As used herein, the term “enzymatic perhydrolysis” refers to a reaction of a selected substrate with a source of hydrogen peroxide to form a peroxycarboxylic acid, wherein the reaction is catalyzed by an enzyme catalyst having perhydrolysis activity.
As used herein, the term “perhydrolase activity” refers to the enzyme 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 peroxycarboxylic acid product (such as peracetic acid) per minute at a specified temperature. “One unit of enzyme activity” may also be used herein to refer to the amount of peroxycarboxylic acid hydrolysis activity required for the hydrolysis of 1 μmol of peroxycarboxylic acid (e.g., peracetic acid) per minute at a specified temperature.
The present variant CE-7 carbohydrate esterase is characterized by an increase in specific activity in the presence of an anionic surfactant when compared to the perhydrolase from which it was derived (Thermotoga maritima C277T, Published U.S. Patent Application No. 2010-0087529) under the same reaction conditions (i.e., a surfactant concentration similar to that used in typically laundry conditions). As used herein, the “fold increase” in specific activity is measured relative to the specific activity of the parent perhydrolase from which the variant was derived (the Thermotoga maritima C277T perhydrolase (SEQ ID NO: 3) under the same reaction conditions). In one embodiment, the fold increase in specific activity of the variant polypeptide (i.e., variant perhydrolase) relative to the parent perhydrolase (Thermotoga maritima C277T, SEQ ID NO: 3) is at least 1.01, 1.05, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, or 10-fold when compared under identical reaction/assay conditions.
As used herein, “identical assay conditions” or “same assay conditions” refer to the conditions used to measure the peracid formation (i.e., perhydrolysis of a carboxylic acid ester substrate) specific activity of the variant polypeptide in the presence of anionic surfactant relative to the respective specific activity of the polypeptide from which it is was derived. The assay conditions used to measure the respective specific activities should be as close to identical as possible such that only the structure of the polypeptide having perhydrolytic activity varies. In one embodiment, the assay conditions comprise about 6 mg/mL anionic surfactant. In a preferred aspect, the anionic surfactant in the assay conditions is linear alkyl benzene sulfonic acid (LAS). In yet a further preferred aspect, the anionic surfactant in the assay conditions is about 6 mg/mL linear alkyl benzene sulfonic acid.
As used herein, the terms “enzyme catalyst” and “perhydrolase catalyst” refer to a catalyst comprising an enzyme (i.e., a polypeptide) 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 (for example, 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.
The present enzyme catalyst comprises a variant polypeptide having perhydrolytic activity and is structurally classified as a member 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.). The CE-7 family of enzymes has been demonstrated to be particularly effective for producing peroxycarboxylic acids from a variety of carboxylic acid ester substrates when combined with a source of peroxygen (See PCT publication No. WO2007/070609 and U.S. Patent Application Publication No. 2008-0176299 and U.S. Pat. Nos. 7,951,566 and 7,723,083 to DiCosimo et al.; each herein incorporated by reference in their entireties). The CE-7 enzyme family includes cephalosporin C deacetylases (CAHs, E.C. 3.1.1.41) and acetyl xylan esterases (AXEs; E.C. 3.1.1.72). Members of the CE-7 enzyme family share a conserved signature motif (Vincent et al., J. Mol. Biol., 330:593-606 (2003)).
As used herein, the terms “signature motif” and “CE-7 signature motif” refer to conserved structures shared among a family of enzymes having a perhydrolytic activity.
As used herein, “structurally classified as a CE-7 enzyme”, “structurally classified as a carbohydrate esterase family 7 enzyme”, “structurally classified as a CE-7 carbohydrate esterase”, and “CE-7 perhydrolase” will be used to refer to enzymes having perhydrolysis activity that are structurally classified as a CE-7 carbohydrate esterase based on the presence of the CE-7 signature motif (Vincent et al., supra). The “signature motif” for CE-7 esterases comprises three conserved motifs (residue position numbering relative to reference sequence SEQ ID NO: 2; the wild-type Thermotoga maritima acetyl xylan esterase):
a) Arg118-Gly119-Gln120,
b) Gly186-Xaa187-Ser188-Gln189-Gly190, and
c) His303-Glu304.
Typically, the Xaa at amino acid residue position 187 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 187 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 272-274 of SEQ ID NO: 2) that may be used to further define a member of the CE-7 carbohydrate esterase family. In a further embodiment, the signature motif defined above includes a fourth conserved motif defined as:
The Xaa at amino acid residue position 273 is typically isoleucine, valine, or methionine. The fourth motif includes the aspartic acid residue (bold) belonging to the catalytic triad (Ser188-Asp274-His303).
As used herein, the terms “cephalosporin C deacetylase” and “cephalosporin C acetyl hydrolase” refer 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). Enzymes classified as cephalosporin C deacetylases have been shown to often have significant perhydrolytic activity (U.S. Pat. No. 7,951,566 and U.S. Patent Application Publication No. 2008-0176299 to DiCosimo et al.).
As used herein, “acetyl xylan esterase” refers to an enzyme (E.C. 3.1.1.72; AXEs) that catalyzes the deacetylation of acetylated xylans and other acetylated saccharides. Enzymes classified as acetyl xylan esterases have been shown to have significant perhydrolytic activity (U.S. Pat. Nos. 7,951,566 and 7,723,083 and U.S. Patent Application Publication No. 2008-0176299; each to DiCosimo et al.).
As used herein, the term “Thermotoga maritima” refers to a bacterial cell reported to have acetyl xylan esterase activity (GENBANK®NP—227893.1). In one aspect, the Thermotoga maritima strain is Thermotoga maritima MSB8. The amino acid sequence of the wild-type enzyme having perhydrolase activity from Thermotoga maritima is provided as SEQ ID NO: 2.
As used herein, the terms “variant”, “variant polypeptide”, and “variant enzyme catalyst” refer to an enzyme catalyst comprising at least one polypeptide (i.e., a perhydrolase) having perhydrolytic activity wherein the polypeptide comprises at least one amino acid change relative to the enzyme/polypeptide from which it was derived (i.e., Thermotoga maritima C277T perhydrolase). Several variant polypeptides are provided herein having perhydrolytic activity and are characterized by an increase in specific activity when measured in the presence of an anionic surfactant relative to the Thermotoga maritima C277T acetyl xylan esterase having amino acid sequence SEQ ID NO: 3.
For a particular variant perhydrolase, amino acid substitutions are specified with reference to the wild type Thermotoga maritima amino acid sequence (SEQ ID NO: 2). The wild-type amino acid (denoted by the standard single letter abbreviation) is followed by the amino acid residue position of SEQ ID NO: 2 followed by the amino acid of the variant (also denoted by the standard single letter abbreviation). For example, “C277T” describes a change in SEQ ID NO: 2 at amino acid residue position 277 where cysteine was changed to threonine. The variant polypeptide may be comprised of multiple point substitutions. For example, R16E/C277T refers to a variant polypeptide having two point substitutions: 1) a change at amino acid residue position 16 where an arginine was changed to a glutamic acid, and 2) a change at position 277 where a cysteine was changed to a threonine.
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:
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 present enzyme can be used to produce an efficacious concentration of at least one peroxycarboxylic acid useful to reduce and/or eliminate the presence of the viable biological contaminants. In a preferred embodiment, the biological 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 “sanitary” means of or relating to the restoration or preservation of health, typically by removing, preventing or controlling an agent that may be injurious to health. As used herein, the term “sanitize” means to make sanitary. As used herein, the term “sanitizer” refers to a sanitizing agent. As used herein the term “sanitization” refers to the act or process of sanitizing.
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. Peroxycarboxylic acids 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. Peroxycarboxylic acids 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 log10 reduction in viable microorganisms after treatment. In one aspect, the targeted reduction in viable microorganisms after treatment is at least a 3-log10 reduction, more preferably at least a 4-log10 reduction, and most preferably at least a 5-log10 reduction. In another aspect, the minimum biocidal concentration is at least a 6-log10 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 0.5 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, such as sodium percarbonate. As described herein, the concentration of the hydrogen peroxide provided by the peroxygen compound in the aqueous reaction formulation is initially at least 0.5 mM or more upon combining the reaction components. In one embodiment, the hydrogen peroxide concentration in the aqueous reaction formulation is at least 1 mM. In another embodiment, the hydrogen peroxide concentration in the aqueous reaction formulation is at least 10 mM. In another embodiment, the hydrogen peroxide concentration in the aqueous reaction formulation is at least 100 mM. In another embodiment, the hydrogen peroxide concentration in the aqueous reaction formulation is at least 200 mM. In another embodiment, the hydrogen peroxide concentration in the aqueous reaction formulation is 500 mM or more. In yet another embodiment, the hydrogen peroxide concentration in the aqueous reaction formulation is 1000 mM or more. The molar ratio of the hydrogen peroxide to enzyme substrate, such as triglyceride, (H2O2:substrate) in the aqueous reaction formulation may be from about 0.002 to 20, preferably about 0.1 to 10, and most preferably about 0.5 to 5.
As used herein, the term “benefit agent” refers to a material that promotes or enhances a useful advantage, a favorable/desirable effect or benefit. In one embodiment, a process is provided whereby a benefit agent, such as a composition comprising a peroxycarboxylic acid, is applied to a textile or article of clothing to achieve a desired benefit, such as disinfecting, bleaching, destaining, deodorizing, and any combination thereof. Personal care applications may also be comprised of at least one anionic surfactant. In another embodiment, the present variant polypeptide having perhydrolytic activity may be used to produce a peracid-based benefit agent for use in personal care products (such as hair care products, skin care products, nail care products or oral care products). In one embodiment, a personal care product is provided comprising the variant perhydrolase having amino acid sequence SEQ ID NO: 4 and a cosmetically/dermally acceptable carrier medium. The personal care products are formulated to provide a safe and efficacious concentration of the desired peracid benefit agent.
The compositions and methods described herein may further comprise one or more dermatologically or cosmetically acceptable components known or otherwise effective for use in hair care, skin care, nail care or other personal care products, provided that the optional components are physically and chemically compatible with the essential components described herein, or do not otherwise unduly impair product stability, aesthetics, or performance. Non-limiting examples of such optional components are disclosed in International Cosmetic Ingredient Dictionary, Ninth Edition, 2002, and CTFA Cosmetic Ingredient Handbook, Tenth Edition, 2004.
In one embodiment, the dermatologically/cosmetically acceptable carrier may comprise from about 10 wt % to about 99.9 wt %, alternatively from about 50 wt % to about 95 wt %, and alternatively from about 75 wt % to about 95 wt %, of an acceptable carrier. Carriers suitable for use with the composition(s) may include, for example, those used in the formulation of hair sprays, mousses, tonics, gels, skin moisturizers, lotions, and leave-on conditioners. The carrier may comprise water; organic oils; silicones such as volatile silicones, amino or non-amino silicone gums or oils, and mixtures thereof; mineral oils; plant oils such as olive oil, castor oil, rapeseed oil, coconut oil, wheatgerm oil, sweet almond oil, avocado oil, macadamia oil, apricot oil, safflower oil, candlenut oil, false flax oil, tamanu oil, lemon oil and mixtures thereof; waxes; and organic compounds such as C2-C10 alkanes, acetone, methyl ethyl ketone, volatile organic C1-C12 alcohols, esters (with the understanding that the choice of ester(s) may be dependent on whether or not it may act as a carboxylic acid ester substrates for the CE-7 perhydrolases) of C1-C20 acids and of C1-C8 alcohols such as methyl acetate, butyl acetate, ethyl acetate, and isopropyl myristate, dimethoxyethane, diethoxyethane, C10-C30 fatty alcohols such as lauryl alcohol, cetyl alcohol, stearyl alcohol, and behenyl alcohol; C10-C30 fatty acids such as lauric acid and stearic acid; C10-C30 fatty amides such as lauric diethanolamide; C10-C30 fatty alkyl esters such as C10-C30 fatty alkyl benzoates; hydroxypropylcellulose, and mixtures thereof. In one embodiment, the carrier comprises water, fatty alcohols, volatile organic alcohols, and mixtures thereof.
The present variant polypeptides were derived from the Thermotoga maritima C277T acetyl xylan esterase that has been previously demonstrated to have significant perhydrolytic activity for producing peroxycarboxylic acids from carboxylic acid esters and a source of peroxygen, such as hydrogen peroxide (U.S. Patent Application Publication No. 2008-0176299 and 2010-0087529, each to DiCosimo et al.).
Libraries of variant polypeptides were created from the C277T Thermotoga maritima perhydrolase (SEQ ID NO: 3) and assayed for an increase in the specific activity in the presence of an anionic surfactant (to simulate laundry care conditions) for producing peroxycarboxylic acids from carboxylic acid ester substrates. The assay conditions used to measure the respective specific activities should be as close to identical as possible such that only the structure of the polypeptide having perhydrolytic activity varies. In one embodiment, reactions used to measure specific activity are run at ca. 25° C. in reactions containing 0.75 mM triacetin, 1.4 mM hydrogen peroxide and approximately 6 μg/mL of heat-treated extract supernatant total soluble protein from E. coli strain KLP18 expressing the C277T perhydrolase or variant perhydrolase, in the presence of 6 mg/mL of an anionic surfactant, 35 mM sodium bicarbonate buffer, and an initial pH of 10.8 (see Examples 2 and 3).
Suitable Reaction Conditions for the Enzyme-Catalyzed Preparation of Peroxycarboxylic Acids from Carboxylic Acid Esters and Hydrogen Peroxide
A process is provided to produce an aqueous formulation comprising at least one peroxycarboxylic acid by reacting carboxylic acid esters and an inorganic peroxide (such as, e.g., hydrogen peroxide, sodium perborate or sodium percarbonate) in the presence of an enzyme catalyst having perhydrolysis activity, wherein the enzyme catalyst comprises, in one embodiment, a polypeptide having an amino acid sequence selected from the group consisting of SEQ ID NOs: 4, 5, 6, and 7. In a further embodiment, the polypeptide has the amino acid sequence of SEQ ID NO: 4.
In one embodiment, suitable substrates include one or more esters provided by the following formula:
[X]mR5
In another embodiment, R6 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, R6 is C2 to C7 linear hydrocarbyl moiety, optionally substituted with hydroxyl groups, and/or optionally comprising one or more ether linkages.
In one embodiment, the suitable substrate may include 2-acetoxybenzoic acid, 3-acetoxybenzoic acid, 4-acetoxybenzoic acid or mixtures thereof.
In another embodiment, suitable substrates also include one or more glycerides of the formula:
wherein R1=C1 to C21 straight chain or branched chain alkyl optionally substituted with an hydroxyl or a C1 to C4 alkoxy group and R3 and R4 are individually H or R1C(O). In one embodiment, the suitable substrate is a glyceride of the above formula wherein R1=C1 to C7 straight chain or branched chain alkyl optionally substituted with an hydroxyl or a C1 to C4 alkoxy group and R3 and R4 are individually H or R1C(O).
In another aspect, suitable substrates may also include one or more esters of the formula:
wherein R1 is a C1 to C7 straight chain or branched chain alkyl optionally substituted with an hydroxyl or a C1 to C4 alkoxy group and R2 is a C1 to C10 straight chain or branched chain alkyl, alkenyl, alkynyl, aryl, alkylaryl, alkylheteroaryl, heteroaryl, (CH2CH2O)n, or (CH2CH(CH3)—O)nH and n is 1 to 10.
Suitable substrates may also include one or more acylated saccharides selected from the group consisting of acylated mono-, di-, and polysaccharides. In another embodiment, the acylated saccharides are selected from the group consisting of acetylated xylan; fragments of acetylated xylan; acetylated xylose (such as xylose tetraacetate); acetylated glucose (such as α-D-glucose pentaacetate; β-D-glucose pentaacetate); β-D-galactose pentaacetate; sorbitol hexaacetate; sucrose octaacetate; β-D-ribofuranose-1,2,3,5-tetraacetate, tri-O-acetyl-D-galactal; tri-O-acetyl-D-glucal, tetraacetylxylofuranose; α-D-glucopyranose pentaacetate; α-D-mannopyranose pentaacetate; 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; tri-O-acetyl-D-glucal; sucrose octaacetate and acetylated cellulose.
In another embodiment, suitable substrates are 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-D-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 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 (such as 1,3-propanediol diacetate, 1,4-butanediol diacetate, etc.). In a further embodiment, the substrate is propylene glycol diacetate (PGDA), ethylene glycol diacetate (EGDA), or a mixture thereof.
In another embodiment, suitable substrates are 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 embodiment, suitable 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 substrate is selected from the group consisting of diacetin, triacetin, ethyl acetate, and ethyl lactate. In a most preferred embodiment, the suitable substrate comprises triacetin.
The carboxylic acid ester is present in the aqueous reaction formulation at a concentration sufficient to produce the desired concentration of peroxycarboxylic acid upon enzyme-catalyzed perhydrolysis. The carboxylic acid ester need not be completely soluble in the aqueous reaction formulation, but has sufficient solubility to permit conversion of the ester by the perhydrolase catalyst to the corresponding peroxycarboxylic acid. The carboxylic acid ester is present in the aqueous reaction formulation at a concentration of 0.0005 wt % to 40 wt % of the aqueous reaction formulation, preferably at a concentration of 0.005 wt % to 20 wt % of the aqueous reaction formulation, and more preferably at a concentration of 0.01 wt % to 10 wt % of the aqueous reaction formulation. 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 aqueous reaction formulation 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 formulation. Not all of the added carboxylic acid ester must immediately dissolve in the aqueous reaction formulation, and after an initial mixing of all reaction components, additional continuous or discontinuous mixing is optional.
The peroxycarboxylic acids produced by the present reaction components may vary depending upon the selected substrates, so long as the present enzyme catalyst is used. In one embodiment, the peroxycarboxylic acid produced is peracetic acid, perpropionic acid, perbutyric acid, peroctanoic acid, perlactic acid, perglycolic acid, permethoxyacetic acid, per-β-hydroxybutyric acid, or mixtures thereof.
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. Alternatively, hydrogen peroxide can be generated in situ by the reaction of a substrate and oxygen catalyzed by an enzyme having oxidase activity (including, but not limited to, glucose oxidase, galactose oxidase, sorbitol oxidase, hexose oxidase, alcohol oxidase, glycerol oxidase, monoamine oxidase, glycolate oxidase, lactate oxidase, pyruvate oxidase, oxalate oxidase, choline oxidase, cholesterol oxidase, pyranose oxidase, carbon/alcohol oxidase, L-amino acid oxidase, glycine oxidase, glutamate oxidase, lysine oxidase, and uricase). The concentration of peroxygen compound in the aqueous reaction formulation may range from 0.0017 wt % to about 50 wt %, preferably from 0.017 wt % to about 40 wt %, more preferably from 0.17 wt % to about 30 wt %.
Many perhydrolase catalysts (such as whole cells, permeabilized whole cells, and partially purified whole cell extracts) have been reported to have catalase activity (EC 1.11.1.6). Catalases catalyze the conversion of hydrogen peroxide into oxygen and water. In one aspect, the enzyme catalyst having perhydrolase activity lacks catalase activity. In another aspect, the enzyme catalyst having perhydrolase activity has a sufficiently-low catalase activity that the presence of said catalase activity does not significantly interfere with perhydrolase-catalyzed peroxycarboxylic acid production. In another aspect, a catalase inhibitor is added to the aqueous reaction formulation. 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 concentration is typically about 0.5 mM to about 30 mM, preferably about 10 mM.
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 and katE (see U.S. Pat. No. 7,951,566 to DiCosimo et al.). In another embodiment, the production host is an E. coli strain comprising a down-regulation and/or disruption in both katG and katE catalase genes. An E. coli strain comprising a double-knockout of katG and katE has been prepared and is described as E. coli strain KLP18 (U.S. Pat. No. 7,951,566 to DiCosimo et al.).
The concentration of the catalyst in the aqueous reaction formulation depends on the specific catalytic activity of the catalyst, and is chosen to obtain the desired rate of reaction. The weight of catalyst in perhydrolysis reactions typically ranges from 0.0001 mg to 50 mg per mL of total reaction volume, preferably from 0.0005 mg to 10 mg per mL, more preferably from 0.0010 mg to 2.0 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 peroxycarboxylic acid generated by the combination of chemical perhydrolysis and enzymatic perhydrolysis of the carboxylic acid ester is sufficient to provide an effective concentration of peroxycarboxylic acid for disinfection, bleaching, sanitization, deodorizing or destaining at a desired pH. In another aspect, the peroxycarboxylic acid is generated at a safe and efficacious concentration suitable for use in a personal care product to be applied to the hair, skin, nails or tissues of the oral cavity, such as tooth enamel, tooth pellicle or the gums. In another aspect, the present methods provide combinations of enzymes and enzyme substrates to produce the desired effective concentration of peroxycarboxylic acid, where, in the absence of added enzyme, there is a significantly lower concentration of peroxycarboxylic acid produced. Although there may be some 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 peroxycarboxylic acid generated to provide an effective concentration of peroxycarboxylic acid in the desired applications, and a significant increase in total peroxycarboxylic acid concentration is achieved by the addition of an appropriate perhydrolase catalyst to the aqueous reaction formulation.
In one aspect of the invention, the concentration of peroxycarboxylic acid generated (e.g. peracetic acid) by the enzymatic perhydrolysis is at least about 2 ppm, preferably at least 20 ppm, preferably at least 100 ppm, more preferably at least about 200 ppm peroxycarboxylic acid, more preferably at least 300 ppm, more preferably at least 500 ppm, more preferably at least 700 ppm, more preferably at least about 1000 ppm peroxycarboxylic acid, more preferably at least about 2000 ppm peroxycarboxylic acid, most preferably at least 10,000 ppm peroxycarboxylic acid within 5 minutes more preferably within 1 minute of initiating the enzymatic perhydrolysis reaction. In a second aspect of the invention, the concentration of peroxycarboxylic acid generated (e.g. peracetic acid) by the enzymatic perhydrolysis is at least about 2 ppm, preferably at least 20 ppm, preferably at least 30 ppm, more preferably at least about 40 ppm peroxycarboxylic acid, more preferably at least 50 ppm, more preferably at least 60 ppm, more preferably at least 70 ppm, more preferably at least about 80 ppm peroxycarboxylic acid, most preferably at least 100 ppm peroxycarboxylic acid within 5 minutes, more preferably within 1 minute, of initiating the enzymatic perhydrolysis reaction (i.e., time measured from combining the reaction components to form the formulation).
The aqueous formulation comprising the peroxycarboxylic acid may be optionally diluted with diluent comprising water, or a solution predominantly comprised of water, to produce a formulation with the desired lower target concentration of peroxycarboxylic acid. In one aspect, the reaction time required to produce the desired concentration (or concentration range) of peroxycarboxylic acid is about 20 minutes or less, preferable about 5 minutes or less, most preferably about 1 minute or less.
In other aspects, the surface or inanimate object contaminated with a concentration of a biological contaminant(s) is contacted with the peroxycarboxylic acid 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 another aspect, the peroxycarboxylic acid formed in accordance with the processes describe herein is used in a laundry care application wherein the peroxycarboxylic acid is contacted with clothing or a textile to provide a benefit, such as disinfecting, bleaching, destaining, deodorizing and/or a combination thereof. The peroxycarboxylic acid may be used in a variety of laundry care products including, but not limited to, laundry or textile pre-wash treatments, laundry detergents or additives, stain removers, bleaching compositions, deodorizing compositions, and rinsing agents. In one embodiment, the present process to produce a peroxycarboxylic acid for a target surface is conducted in situ.
In the context of laundry care applications, the term “contacting an article of clothing or textile” means that the article of clothing or textile is exposed to a formulation disclosed herein. To this end, there are a number of formats the formulation may be used to treat articles of clothing or textiles including, but not limited to, liquid, solids, gel, paste, bars, tablets, spray, foam, powder, or granules and can be delivered via hand dosing, unit dosing, dosing from a substrate, spraying and automatic dosing from a laundry washing or drying machine. Granular compositions can also be in compact form; liquid compositions can also be in a concentrated form.
When the formulations disclosed herein are used in a laundry washing machine, the formulation can further contain components typical to laundry detergents. For example, typical components include, but are not limited to, surfactants, bleaching agents, bleach activators, additional enzymes, suds suppressors, dispersants, lime-soap dispersants, soil suspension and anti-redeposition agents, softening agents, corrosion inhibitors, tarnish inhibitors, germicides, pH adjusting agents, non-builder alkalinity sources, chelating agents, organic and/or inorganic fillers, solvents, hydrotropes, optical brighteners, dyes, and perfumes. In one embodiment, the surfactant(s) used in the laundry care formulation is present at a concentration of about 6 mg/mL. In a further embodiment, the surfactant(s) used in the laundry care formulation are anionic surfactants. In another aspect, the anionic surfactant comprises linear alkyl benzene sulfonic acid or salt thereof.
The present formulations can also be used as detergent additive products in solid or liquid form. Such additive products are intended to supplement or boost the performance of conventional detergent compositions and can be added at any stage of the cleaning process.
In connection with the present systems and methods for laundry care where the peracid is generated for one or more of bleaching, stain removal, and odor reduction, the concentration of peracid generated (e.g., peracetic acid) by the perhydrolysis of at least one carboxylic acid ester may be at least about 2 ppm, preferably at least 20 ppm, more preferably at least 40 ppm, and even more preferably at least about 100 ppm peracid. In connection with the present systems and methods for laundry care where the peracid is generated for disinfection or sanitization, the concentration of peracid generated (e.g., peracetic acid) by the perhydrolysis of at least one carboxylic acid ester may be at least about 40 ppm, more preferably at least 80 ppm, and most preferably at least 100 ppm peracid within 10 minutes, preferably within 5 minutes, and most preferably within 1 minute of initiating the perhydrolysis reaction. The product formulation comprising the peracid may be optionally diluted with water, or a solution predominantly comprised of water, to produce a formulation with the desired lower concentration of peracid. In one aspect of the present methods and systems, 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.
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 aqueous reaction formulation (approximately 0° C.) to about 85° C., with a preferred range of reaction temperature of from about 5° C. to about 75° C.
The pH of the aqueous reaction formulation while enzymatically producing peroxycarboxylic acid is maintained at a pH ranging from about 5.0 to about 11.5, preferably about 6.5 to about 11.0, and yet even more preferably about 7.5 to about 11.0. In one embodiment, the pH of the aqueous reaction formulation ranges from about 10.5 to about 11.0 for at least 30 minutes after combining the reaction components. The pH of the aqueous reaction formulation may be adjusted or controlled by the addition or incorporation of a suitable buffer, including, but not limited to, phosphate, pyrophosphate, bicarbonate, acetate, or citrate. In one embodiment, the buffer is selected from a phosphate buffer, a bicarbonate buffer, or a buffer formed by the combination of hard ward (tap water to simulate laundry care applications) and percarbonate (from sodium percarbonate used to generate hydrogen peroxide). The concentration of buffer, when employed, is typically from 0.1 mM to 1.0 M, preferably from 1 mM to 300 mM, most preferably from 10 mM to 100 mM. In another aspect of the present invention, no buffer is added to the reaction mixture while enzymatically producing peroxycarboxylic acid.
In yet another aspect, the enzymatic perhydrolysis aqueous reaction formulation may contain an organic solvent that acts as a dispersant to enhance the rate of dissolution of the carboxylic acid ester in the aqueous reaction formulation. 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 (synthetic layered silicate), corn starch, PVP, CARBOWAX® (polyethylene glycol and/or methoxypolyethylene glycol), CARBOPOL® (acrylates crosspolymer), CABOSIL® (synthetic amorphous fumed silicon dioxide), 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, linear alkyl benzene sulphonic acid (e.g., C10-C16), alkene sulfonates; and d) amphoteric and zwitterionic surfactants such as aminocarboxylic acids, aminodicarboxylic acids, alkybetaines, and mixtures thereof. In one embodiment, compositions and methods using the present variant perhydrolytic enzyme comprises C10-C16 linear alkyl benzene sulphonic acid (“LAS”). 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 (etidronic acid), DEQUEST® 0520 (phosphonate), DEQUEST® 0531 (phosphonate), stabilizers of enzyme activity (e.g., polyethylene glycol (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 aqueous reaction formulation that generate the desired concentration of peroxycarboxylic acid are contacted with the surface or inanimate object to be disinfected and/or bleached or destained, generating the desired concentration of peroxycarboxylic acid. In some embodiments, the components of the aqueous reaction formulation 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.
The peroxycarboxylic acids, once 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 a source of peroxygen (such as hydrogen 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 peroxycarboxylic acid 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 (e.g., powder or 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 yet a further aspect, the perhydrolase catalyst may comprise the contents contained within a separate compartment of a dissolvable or porous pouch that has at least one additional compartment for the containment contents comprising the ester substrate and/or source of peroxide. 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.
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 HPLC 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 (see U. Pinkernell et al., The Analyst 122:567-571 (1997), S. Minning, et al., Analytica Chimica Acta 378:293-298 (1999) and WO 2004/058961 A1) as described in U.S. Pat. No. 7,951,566.
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 peroxycarboxylic acids, 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, 5th edition, Lippincott Williams & Wilkins, Philadelphia, Pa., USA; 2001).
The enzyme catalyst-generated peroxycarboxylic acid produced according to the present method can be used in a variety of hard surface/inanimate object applications for reduction of concentrations of biological contaminants, such as decontamination of medical instruments (e.g., endoscopes), textiles (such as garments and 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 peroxycarboxylic acids may be used in formulations designed to inactivate prions (e.g., certain proteases) to additionally provide biocidal activity (see U.S. Pat. No. 7,550,420 to DiCosimo et al.).
In one aspect, the peroxycarboxylic acid composition is useful as a disinfecting agent for non-autoclavable medical instruments and food packaging equipment. As the peroxycarboxylic acid-containing formulation may be prepared using GRAS (generally recognized as safe) or food-grade components (enzyme, enzyme substrate, hydrogen peroxide, and buffer), the enzyme-generated peroxycarboxylic acid may also be used for decontamination of animal carcasses, meat, fruits and vegetables, or for decontamination of prepared foods. The enzyme-generated peroxycarboxylic acid may be incorporated into a product whose final form is a powder, liquid, gel, film, solid or aerosol. The enzyme-generated peroxycarboxylic acid may be diluted to a concentration that still provides an efficacious decontamination.
The compositions comprising an efficacious concentration of peroxycarboxylic acid can be used to disinfect surfaces and/or objects contaminated (or suspected of being contaminated) with biological contaminants, such as 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 peroxycarboxylic acid in contact with the surface or inanimate object suspected of contamination with a biological contaminant 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 peroxycarboxylic acid solution or composition comprising an efficacious concentration of peroxycarboxylic acid, or a solution or composition that forms an efficacious concentration of peroxycarboxylic acid, with the surface or inanimate object suspected of being contaminated with a concentration of a biological contaminant. 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. In one embodiment, the cleaning agent comprises at least one anion surfactant, such as linear alkyl benzene sulphonic acid.
The compositions comprising an efficacious concentration of peroxycarboxylic acid 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 peroxycarboxylic acid 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 biological contaminants. 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, ClO2), 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 C1-C6 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 peroxycarboxylic acids formed by the process can be used to reduce the concentration of viable biological contaminants (such as a 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 biological contaminants. 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 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 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, wood pulp, paper, vinyl, linoleum, and carpet.
The peroxycarboxylic acids formed by the present process may be used to provide a benefit to an article of clothing or a textile including, but not limited to, disinfecting, sanitizing, bleaching, destaining, and deodorizing. The peroxycarboxylic acids formed by the present process may be used in any number of laundry care products including, but not limited to, textile pre-wash treatments, laundry detergents, laundry detergents or additives, stain removers, bleaching compositions, deodorizing compositions, and rinsing agents, to name a few.
The peroxycarboxylic acids formed by the present process can be used in one or more steps of the wood pulp or paper pulp bleaching/delignification process, particularly where peracetic acid is used (for example, see EP1040222 B1 and U.S. Pat. No. 5,552,018 to Devenyns, J.).
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, Kluyveromyces, Candida, Hansenula, Yarrowia, Salmonella, Bacillus, Acinetobacter, Zymomonas, Agrobacterium, Erythrobacter, 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 Bacillus subtilis or Escherichia coli.
A variety of culture methodologies may be applied to produce the perhydrolase catalyst. Large-scale production of a specific gene product over expressed from a recombinant microbial host may be produced by batch, fed-batch or continuous culture methodologies. 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).
In one embodiment, commercial production of the desired perhydrolase catalyst is 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.
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 enzyme 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 enzyme 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 enzyme catalyst solution. The solution containing the desired enzyme catalyst may then be separated from the precipitated cell debris and protein produced during the heat-treatment step by membrane filtration or centrifugation, and the resulting partially-purified enzyme catalyst solution concentrated by additional membrane filtration, then optionally mixed with an appropriate excipient (for example, maltodextrin, trehalose, sucrose, lactose, sorbitol, mannitol, phosphate buffer, citrate buffer, or mixtures thereof) and spray-dried to produce a solid powder comprising the desired enzyme catalyst. Alternatively, the resulting partially-purified enzyme catalyst solution prepared as described above may be optionally concentrated by additional membrane filtration, and the partially-purified enzyme catalyst solution or resulting enzyme concentrate is then optionally mixed with one or more stabilizing agents (e.g., glycerol, sorbitol, propylene glycol, 1,3-propanediol, polyols, polymeric polyols, polyvinylalcohol or mixtures thereof), one or more salts (e.g., sodium chloride, sodium sulfate, potassium chloride, potassium sulfate, or mixtures thereof), and one or more biocides, and maintained as an aqueous solution until used.
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.
The following examples are provided to demonstrate different embodiments. 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 methods disclosed herein, 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 presently disclosed methods.
All reagents and materials were obtained from HiMedia laboratories (Mumbai, India), Bio-Rad (CA, USA), Invitrogen (CA, USA), Fisher Scientific (PA, USA) 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), “μL” 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 H2O” 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, “IPTG” means isopropyl β-D-1-thiogalactopyranoside, “EDTA” means ethylenediaminetetraacetic acid, and “ABTS” means 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid.
The coding sequence of a Thermotoga maritima acetyl xylan esterase with C277T variant encoded DNA was synthesized using codons optimized for expression in E. coli. The polypeptide sequence of the C277T Thermotoga maritima acetyl xylan esterase enzyme is provided as SEQ ID NO: 3.
Synthesized DNA sequence was subcloned into pUC19 vector (NEB; New England Biolabs, Ipswitch, Mass.) to generate the plasmid known as pNS-001 (GENEART® (gene synthesis), Regensburg, Germany; now a division of Invitrogen Life Sciences Corp., Carlsbad, Calif.). Select positively charged amino acids on the enzyme surface were replaced with either a negatively-charged residue (glutamic acid) or with neutral-charged amino acid residues (alanine, serine or glutamine) to enhance surfactant resistance. Accordingly, a library of 69 variants of C277T acetyl xylan esterase enzymes was generated in pUC19 vector (GENEART®).
E. coli KLP18 (see U.S. Patent Application Publication No. 2008-0176299) was transformed with these plasmid variants and plated onto LB plates supplemented with 0.1 mg/mL ampicillin. Single colonies from each library variants were grown in LB medium supplemented with 0.1 mg/mL ampicillin overnight and glycerol stocks were prepared as per standard methods.
Screening of variants with increased enzyme activity in the presence of surfactant required accurate quantitation of perhydrolase amount in the reaction assay mix. Quantitation employed a two-step approach: a) the total soluble protein in heat purified cell extracts from the library obtained as described in Example 3 was quantitated by Bradford method of protein assay; then b) the amounts of perhydrolase enzyme in these heat purified cell extracts were measured relative to the C277T control by densitometry as follows. Heat purified cell extracts (2.5 μg of total soluble protein per lane) containing the perhydrolase variants were electrophoresed in NuPAGE Novex Bis-Tris 4-12% gel in 1×MES running buffer for 60 minutes, alongside an identical quantity of total soluble protein from heat purified cell extract of the control C277T variant perhydrolase enzyme. The gel was stained with SIMPLYBLUE™ safe stain overnight and then destained in water for 6-8 hours. The gel was then scanned in GS-800 CALIBRATED™ densitometer (Bio-Rad laboratories, USA) and bands were quantitated using QUANTITY ONE® software version 4.6.9. Lanes were detected automatically by ‘auto frame lanes’ option in QUANTITY ONE® software. In addition, these lanes were visually examined for accuracy. The protein band quantitation was done utilizing the default parameters: sensitivity=10.00, lane width=2.477 mm, min density=0.00%, noise filter=4.00, shoulder sensitivity=1.0, size scale=5, and relative quantity calculation option % of lane (% of lane that means that the total intensity in the lane including bands and the intensity between bands will equal 100 percent and the band that is selected is reported as a fraction thereof). All relative quantity numbers were then normalized with respect to the C277T perhydrolase 37 kDa specific band, which was given a value of 1. Accordingly, based on the relative amount of perhydrolase specific band quantity in each heat purified cell extract containing perhydrolase variant in comparison with C277T control, proportional amount of variant perhydrolase was added in the reaction mix to determine the enzyme activity of the variants in presence of surfactant.
Glycerol stocks of the library variants were inoculated into respective inoculation tubes containing 5 mL Luria Bertani (LB) broth containing 0.1 mg/mL of ampicillin and grown at 37° C. with shaking speed of 250 rpm for 16-17 hours. These cells were next inoculated (1%) into 125-mL flasks containing 20 mL LB broth with 0.1 mg/mL of ampicillin and incubated at 37° C. with shaking at 250 rpm.
The growing cultures were induced with 0.5 mM of IPTG when they reached an OD600nm between 0.5-0.7. Following induction, cells were additionally grown for 5 hours and then harvested by centrifugation at 6200 rpm for 15 minutes. Cell pellets were stored in −80° C. Cells pellets were thawed, and 2 mL of 25 mg/mL CELLYTIC™ Express (non-denaturing protein extraction formulation; Sigma Aldrich, St. Louis, Mo.) was added to each cell pellet to lyse the cells. After incubation for 60 minutes with shaking at room temperature of ˜22° C., cell lysates were centrifuged at 12000 rpm for 15 min and the supernatant was collected. The cell lysate supernatant was subjected to heat treatment for 20 min at 75° C. in a dry bath (after the dry bath reached the desired temperature of 75° C.). Heat-treated cell lysate supernatants were centrifuged at 12000 rpm for 20 min to remove precipitated proteins and the resultant supernatants obtained (referred to as “heat purified cell extract” or “heat-treated total soluble protein”) were aliquoted into vials of 0.3 mL each and stored in −80° C. The resulting heat purified cell extracts were quantified for total soluble protein amount by Bradford assay and relative perhydrolase variant amount in the heat purified cell extracts was determined by densitometry as described in Example 2.
Peracetic acid (PAA) concentrations were determined using an ABTS assay as described by U. Pinkernell et al., The Analyst 122:567-571 (1997). Total reaction volume of 2 mL comprised 0.75 mM triacetin and 1.4 mM H2O2 in a reaction buffer of 35 mM sodium carbonate buffer containing 6 g/L of linear alkyl benzene sulphonic acid (LAS). Heat purified cell extract containing C277T perhydrolase was added to the control reaction to produce a concentration of 6 ppm of total soluble protein in the reaction mixture, while heat purified cell extracts containing other perhydrolase variants were added according to proportional concentration derived from densitometry as described in Example 2, resulting in a concentration of variant perhydrolase in the reaction mixture equivalent to the concentration of C277T in the control reaction. All reactions were performed at ˜22° C. Time points of 3 minutes and 10 minutes were chosen to evaluate PAA production by the C277T T. maritima perhydrolase control and the present perhydrolase variants. Enzymatic PAA production was determined by subtracting the chemical production of PAA (reaction with all substrates and reagents except for the perhydrolase) from total PAA produced (PAA produced in a reaction containing 6 ppm of the perhydrolase enzyme). Four perhydrolase variants were identified that demonstrated a measurable increase in enzymatic activity for PAA production (Table 1).
T. maritima C277T sequence
1= (variant enzymatic perhydrolytic activity/enzymatic perhydrolytic activity of T. maritima C277T (control)), in presence of surfactant.
Variants of Thermotoga maritima perhydrolase identified in the preliminary screen (Example 3) were re-grown in Luria Bertani (LB) broth containing 0.1 mg/mL of ampicillin at 37° C. with shaking as described in Example 3 to an OD600nm between 0.5-0.7, at which time IPTG was added to a final concentration of 0.5 mM, and incubation continued for another 5 hours. Cells were processed in an identical manner as described in Example 3 to obtain the heat purified cell extract supernatants containing the variant perhydrolases. These heat purified cell extract supernatants were analyzed for total soluble protein by Bradford protein assay. Accordingly, 2.5 μg of total soluble protein containing each semi-purified variant perhydrolase was electrophoresed in NuPAGE Novex Bis-Tris 4-12% gel in 1×MES running buffer for 60 minutes under standard conditions. Protein expression of the variants was normalized with regards to the 37 kDa perhydrolase specific band of similarly grown and purified C277T Thermotoga maritima variant by densitometry as described in Example 2.
Peracetic acid (PAA) concentrations were determined using an ABTS assay as described in Example 3. Reactions (2 mL) were conducted as described in Example 3. The heat purified cell extracts comprising the variant perhydrolase were added in proportion to the concentration obtained from densitometry as described in Example 2. Time points of 3 minutes and 10 minutes were chosen to evaluate PAA production. Reactions were carried out in duplicates; the results of the enzymatic activity under surfactant conditions are provided in Table 2. Under these reaction conditions, variants 007 (R15E/C277T, SEQ ID NO: 4), 050 (K13S/C277T, SEQ ID NO: 5), 053 (R218S/C277T, SEQ ID NO: 6) and 063 (K316A/K319A/K320A/C277T, SEQ ID NO: 7) demonstrated measurable improvement in enzymatic activity for peracetic acid production when compared to the T. maritima C277T perhydrolase (SEQ ID NO: 3) under the specified conditions.
This application claims the benefit of U.S. Provisional Application No. 61/577,184, filed Dec. 19, 2011, which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61577184 | Dec 2011 | US |
