Enzymatic methods for dyeing with reduced vat and sulfur dyes

BACKGROUND OF THE INVENTION
1 Field of the Invention
The present invention relates to enzymatic methods for dyeing a material with reduced vat dyes and/or reduced sulfur dyes. The present invention also relates to materials dyed by such methods.
2 Description of the Related Art
Dyeing of textiles is often the most important and expensive single step in the manufacture of textile fabrics and garments. In the textile industry, two major types of processes are currently used for dyeing, i.e., batch and continuous. In the batch process, among others, jets, drums, and vat dyers are used. In continuous processes, among others, padding systems are used. See, e.g., I. D. Rattee, In C. M. Carr (editor), The Chemistry of the Textiles Industry, Blackie Academic and Professional, Glasgow, 1995, p. 276.
There are two types of dyes involving a reduction/oxidation mechanism, i.e., vat and sulfur dyes. The purpose of the reduction step in these dyeings is to change the dyestuff from an insoluble form to a soluble form. The oxidation step then converts the soluble dye back to the insoluble dye thereby fixing the dye to the dyed material.
Oxidoreductases, e.g., oxidases and peroxidases, are well known in the art.
One class of oxidoreductases is laccases (benzenediol:oxygen oxidoreductases) which are multi-copper containing enzymes that catalyze the oxidation of phenols and related compounds. Laccase-mediated oxidation results in the production of aromatic radical intermediates from suitable substrates; the ultimate coupling of the intermediates so produced provides a combination of dimeric, oligomeric, and polymeric reaction products. Such reactions are important in nature in biosynthetic pathways which lead to the formation of melanin, alkaloids, toxins, lignins, and humic acids.
Another class of oxidoreductases are peroxidases which oxidize compounds in the presence of hydrogen peroxide.
Laccases have been found to be useful for hair dyeing (see, e.g., WO 95/33836 and WO 95/33837). European Patent No. 0504005 discloses that laccases can be used for dyeing wool at a pH in the range of between 6.5 and 8.0.
U.S. Pat. No. 5,538,517 discloses methods for dyeing keratin fibers with indole or indoline derivatives which produces strong colorations after oxidation with hydrogen peroxide in the presence of a peroxidase.
Saunders et al., Peroxidase, London, 1964, p. 10 ff., disclose that peroxidases act on various amino and phenolic compounds resulting in the production of a color.
Japanese Patent Application publication no. 6-316874 discloses a method for dyeing cotton comprising treating the cotton with an oxygen-containing medium, wherein an oxidoreductase selected from the group consisting of ascorbate oxidase, bilirubin oxidase, catalase, laccase, peroxidase, and polyphenol oxidase is used to generate the oxygen.
Japanese Patent Application publication no. 2-104773 discloses a method for indigoid dyeing of a material using an enzyme selected from the group consisting of napthalene dioxygenase, toluene oxygenase, benzene dioxygenase, indole hydrolase, and xylene oxidase.
WO 91/05839 discloses that oxidases and peroxidases are useful for inhibiting the transfer of textile dyes.
Japanese Patent Application publication no. 08-127976 discloses a method for dyeing a keratin-coated fiber by immobilizing a peroxidase to the fiber, immersing the peroxidase-immobilized fiber in an aqueous solution containing a reduced dye, and enzymatically oxidizing the reduced dye in the presence of hydrogen peroxide with the immobilized peroxidase.
It is an object of the present invention to provide new enzymatic methods for dyeing materials with reduced vat and/or sulfur dyes.
SUMMARY OF THE INVENTION
The present invention relates to methods for dyeing a material, comprising (a) treating the material with a dyeing system which comprises one or more reduced vat dyes and/or one or more reduced sulfur dyes; and (b) oxidizing the one or more reduced vat dyes and/or one or more reduced sulfur dyes adsorbed onto the treated material with an oxidation system comprising (i) an oxygen source and one or more enzymes exhibiting oxidase activity and/or (ii) a hydrogen peroxide source and one or more enzymes exhibiting peroxidase activity, to convert the one or more reduced dyes to their original oxidized insoluble colored forms; wherein the material is a fabric, yarn, fiber, garment or film made of cotton, diacetate, flax, fur, hide, linen, lyocel, polyacrylic, polyamide, polyester, ramie, rayon, triacetate, or viscose.
The present invention also relates to dyed materials obtained by the methods of the present invention.

BRIEF DESCRIPTION OF THE FIGURES
FIG. 1 shows the structures of Indigo, Vat Blue 43, Vat Orange 2, Vat Orange 7, Vat Red 13, Vat Green 3, Vat Yellow 2, and Sulfur Black 1.
FIG. 2 shows the reduction of 0.01% Vat Blue 43 by sodium dithionite as monitored at 626 nm. The initial rate was expressed in -.DELTA.A/min, and the sodium dithionite concentration was expressed by the corresponding reduction extent of Vat Blue 43. The correlation line is Rate=0.001.times.[reduced Vat Blue 43]+0.009 (r.sup.2 =0.842).
FIGS. 3A and 3B show the dependence of the initial re-oxidation rate on the concentration of reduced Vat Blue 43 and Myceliophthora thermophila laccase. The initial rate was expressed in .DELTA.A/min, and the reduced Vat Blue 43 concentration was expressed as the percentage of the initial Vat Blue 43 concentration. The correlation lines were: (A) Rate =0.001[reduced Vat Blue 43]-0.004 (r.sup.2 =0.877); (B) Rate=0.001[reduced Vat Blue 43]+0.004 (r.sup.2 =0.920).
FIG. 4 shows the reduction of 0.01% Vat Orange 7 by sodium dithionite as monitored at 540 nm. The initial rate was expressed in -.DELTA.A/min, and the sodium dithionite concentration was expressed by the corresponding reduction extent of Vat Orange 7. The correlation line was Rate=0.0003.times.[reduced Vat Orange 7]-0.0003 (r.sup.2 =0.902).
FIG. 5 shows the dependence of the initial re-oxidation rate on the concentration of Coprinus cinereus peroxidase. The initial rate was expressed in .DELTA.A/minute. The initial H.sub.2 O.sub.2 concentration was 5.3 mM. The correlation line was Rate=0.0005.times.[Coprinus cinereus peroxidase]-0.0003 (r.sup.2 =0.985).
FIG. 6 shows the oxidation of leuco Sulfur Black 1. Spectral changes were monitored at 627 nm. Initial concentration of leuco Sulfur Black 1: 50 ppm. Trace 1: without Myceliophthora thermophila laccase; trace 2: 0.8 .mu.M Myceliophthora thermophila laccase added at the beginning; and trace 3: 0.8 .mu.M added at 2.5 minutes.

DETAILED DESCRIPTION OF THE INVENTION
Conventional dyeing of a material such as a fabric with a vat or sulfur dye involves sequentially a chemical reduction of the dye to increase its water solubility, adsorption of the reduced dye by the material, and chemical oxidation of the adsorbed reduced dye to essentially its original oxidized insoluble colored form to enhance the color fastness to the material. The chemical oxidation of the reduced dye can be accomplished either by simple exposure to air or more often by complex processing involving chemical oxidants (such as hydrogen peroxide, m-nitrobenzenesulfonate, perborate, hypochlorite, iodate, bromate, or dichromate), harsh conditions (high pH or temperature), and/or expensive/unsafe catalysts (such as metavanadate) (Hughey, 1980; Textile Chemist and Colorist 12: 38-39; U.S. Pat. No. 4,012,192, U.S. Pat. No. 4,036,586; U.S. Pat. No. 4,371,373; John Shore (editor), Cellulosics Dyeing, Society of Dyers and Colourists, West Yorkshire, England, 1995; Horn, 1995, Textile Chemist and Colorist 27: 27-32).
Replacing the chemical re-oxidation step with an enzymatic approach employing one or more oxidoreductases provides several significant advantages. For example, the enzymatic re-oxidation can be used to replace harsh and hazardous chemicals currently used to accomplish the re-oxidation. Moreover, the mild process conditions (e.g., lower temperature and less time) will result in less damage to the fabric and lower energy consumption. Furthermore, the oxidation process may be better controlled during dyeing avoiding uneven dyeing, low color yield, and unsuitable color fastness.
Thus, the present invention relates to methods for dyeing a material, comprising (a) treating the material with a dyeing system which comprises one or more reduced vat dyes and/or one or more reduced sulfur dyes; and (b) oxidizing the one or more reduced vat dyes and/or one or more reduced sulfur dyes adsorbed onto the treated material with an oxidation system comprising (i) an oxygen source and one or more enzymes exhibiting oxidase activity and/or (ii) a hydrogen peroxide source and one or more enzymes exhibiting peroxidase activity, to convert the one or more reduced dyes to their original oxidized insoluble colored forms.
Vat dyes contain two or more keto groups separated by a conjugated system of double bonds and may be any color. They are water-insoluble and have no affinity for a material if they remain in the insoluble state and, thus, can be applied to material, e.g., fabric, only in the reduced state. The reduced state is known as the leuco enolate form of the vat dye.
Vat dyes may be divided into the indigoids, anthraquinoids, and higher condensed aromatic ring systems with a closed system of conjugated double bonds. The chemical constitution of a vat dye influences the properties of the leuco enolate form in the dyeing process, e.g., thermal stability, substantivity, rate of absorption, diffusion into the fiber, and levelling, color, and fastness properties. The vat dyes may be homogeneous dyes or mixtures, each usually containing two, four, or six reducible keto groups.
The most important vat dyes are derivatives of anthraquinone carbazole, anthraquinone oxazole, benzanthrone acridone, dibenzanthrone, flavanthrone, indigo, imidazole, indanthrone, isodibenzanthrone, perylene tetracarboxylic diimide, pyranthrone, pyrazolanthrone, triazinylaminoanthraquinone, and violanthrone. In a preferred embodiment, the vat dye is an anthraquinone carbazole, anthraquinone oxazole, benzanthrone acridone, dibenzanthrone, flavanthrone, indigo, imidazole, indanthrone, isodibenzanthrone, perylene tetracarboxylic diimide, pyranthrone, pyrazolanthrone, triazinylaminoanthraquinone, or violanthrone dye, each of which are optionally substituted with one or more mono-, di- or polycyclic aromatic or polycyclic heteroaromatic compounds. Examples of such mono-, di- or polycyclic aromatic or heteroaromatic compounds include, but are not limited to, acridine, anthracene, azulene, benzene, benzofurane, benzothiazole, benzothiazoline, carboline, carbazole, cinnoline, chromane, chromene, chrysene, fulvene, furan, imidazole, indazole, indene, indole, indoline, indolizine, isothiazole, isoquinoline, isoxazole, naphthalene, naphthylene, naphthylpyridine, oxazole, perylene, phenanthrene, phenazine, phtalizine, pteridine, purine, pyran, pyrazole, pyrene, pyridazine, pyridazone, pyridine, pyriridine, pyrrole, quinazoline, quinoline, quinoxaline, sulfonyl, thiophene, and triazine, each of which are optionally substituted. The anthraquinone carbazole, anthraquinone oxazole, benzanthrone acridone, dibenzanthrone, flavanthrone, indigo, imidazole, indanthrone, isodibenzanthrone, perylene tetracarboxylic diimide, pyranthrone, pyrazolanthrone, triazinylaminoanthraquinone, or violanthrone dye and the one or more optional mono-, di- or polycyclic aromatic or polycyclic heteroaromatic compound substituents thereof may optionally be substituted with one or more functional groups or substituents, wherein each functional group or substituent is selected from the group consisting of halogen; sulfo; sulfonato; sulfamino; sulfanyl; thiol, amino; amido; nitro; azo; imino; carboxy; cyano; formyl; hydroxy; halocarbonyl; carbamoyl; carbamidoyl; phosphonato; phosphonyl; C.sub.1-18 -alkyl; C.sub.1-18 -alkenyl; C.sub.1-18 -alkynyl; C.sub.1-18 -alkoxy; C.sub.1-18 -oxycarbonyl; C.sub.1-18 -oxoalkyl; C.sub.1-18 -alkyl sulfanyl; C.sub.1-18 -alkyl sulfonyl; and C.sub.1-18 -alkyl imino or amino which is substituted with one, two or three C.sub.1-18 -alkyl groups. All C.sub.1-18 -alkyl, C.sub.1-18 -alkenyl and C.sub.1-18 -alkynyl groups may be mono-, di or poly-substituted by any of the preceding functional groups or substituents. For examples of vat dyes, see the Colour Index International, 3.sup.rd Edition, Society of Dyers and Colourists, CD-ROM version, AATCC Box 12215, Research Triangle Park, N.C.
In the methods of the present invention, the vat dye may be any vat dye. Vat dyes are commercially available in the form of liquids, granules, or dedusted powders. Vat dyes are also available as pastes and in pre-reduced or solubilized leuco sulfuric ester forms, e.g., Indigosol O, C.I. Solublized Vat Blue (David R. Waring and Goeffrey Hallas (editors), The Chemistry and Application of Dye, Plenum Press, New York, 1990, pp. 235-236).
In a preferred embodiment, the vat dye is indigo or a derivative thereof, Vat Black, Vat Blue, Vat Brown, Vat Green, Vat Orange, Vat Red, Vat Violet, or Vat Yellow. Examples of these vat dyes include, but are not limited to, Vat Black 8, Vat Black 9, Vat Black 25, Vat Black 27, Vat Blue 1, Vat Blue 2, Vat Blue 3, Vat Blue 4, Vat Blue 5, Vat Blue 6, Vat Blue 7, Vat Blue 8, Vat Blue 9, Vat Blue 10, Vat Blue 11, Vat Blue 12, Vat Blue 13, Vat Blue 14, Vat Blue 15, Vat Blue 16, Vat Blue 18, Vat Blue 19, Vat Blue 20, Vat Blue 21, Vat Blue 22, Vat Blue 25, Vat Blue 26, Vat Blue 28, Vat Blue 29, Vat Blue 30, Vat Blue 31, Vat Blue 32, Vat Blue 33, Vat Blue 35, Vat Blue 36, Vat Blue 37, Vat Blue 40, Vat Blue 41, Vat Blue 42, Vat Blue 43, Vat Blue 47, Vat Blue 48, Vat Blue 64, Vat Blue 66, Vat Blue 72, Vat Blue 74, Vat Brown 1, Vat Brown 3, Vat Brown 9, Vat Brown 14, Vat Brown 16, Vat Brown 22, Vat Brown 31, Vat Brown 44, Vat Green 1, Vat Green 2, Vat Green 3, Vat Green 6, Vat Green 8, Vat Green 9, Vat Green 11, Vat Green 12, Vat Green 13, Vat Orange 2, Vat Orange 7, Vat Orange 9, Vat Orange 11, Vat Orange 15, Vat Orange 18, Vat Red 10, Vat Red 13, Vat Red 14, Vat Red 15, Vat Red 20, Vat Red 23, Vat Red 32, Vat Red 35, Vat Red 42, Vat Violet 1, Vat Violet 9, Vat Violet 10, Vat Violet 24, Vat Yellow 1, Vat Yellow 2, Vat Yellow 6, Vat Yellow 10, Vat Yellow 21, and Vat Yellow 46.
Conversion of an insoluble vat dye to a water-soluble enolate leuco compound generally involves the reduction of the keto groups of the vat dye in the presence of a strong reduction agent and sodium hydroxide to form the sodium enolate leuco compound. The process of converting the water-insoluble vat dye to the soluble leuco form is known as vatting. Since the leuco potential of vat dyes lies between -650 mV and -1000 mV as measured with a calomel electrode, it is important that the reducing agent has a reduction potential in the same range or a more negative reduction potential (see, for example. Alan Johnson (editor), The Theory of Coloration and Textiles, Second Edition, Society of Dyers and Colourists, 1989). The most important reducing agent in vat dyeing is sodium dithionite, which is also known as hydrosulphite or hydros, since it has a reduction potential that is sufficiently negative for all practical requirements. Other reducing agents of limited use include, but are not limited to, hydroxyalkylsulphinates, thiourea dioxide, sodium borohydride, and cathodic reduction.
The reduction of a vat dye may be accomplished using any method known in the art. To prepare a satisfactory vat it is necessary to have an adequate amount of reducing agent and caustic soda. The quantity of reducing agent is determined by that necessary for the particular dye (number of reducible groups, relative molecular mass, content of the pure dye) together with an excess, the quantity of which depends on the temperature, the specific surface area of the dye liquor, the agitation of the liquor, and the amount of air present in the dyeing process. Since sodium hydroxide is consumed both in the vatting process and by the action of atmospheric oxygen, the alkali concentration must be adjusted so the pH of the liquor remains sufficiently high during the dyeing process to prevent formation of the insoluble enolic acid leuco compound. The amount of caustic soda required is determined by the number of keto groups that have to be reduced and by the extent of oxidation due to atmospheric oxygen. Approximately 1 ml of caustic soda (27% by weight) is consumed in the oxidation of 1 g of sodium dithionite. For further details see, for example, John Shore (editor), Colorants and Auxiliaries, Volume 2, Society of Dyers and Colourists, 1990.
Sulfrized vat dyes have features in common with both vat and sulfur dyes (David R. Waring and Goeffrey Hallas (editors), The Chemistry and Application of Dye, Plenum Press, New York, 1990). Sulfurized vat dyes are produced from dye intermediates by a thionation process similar to that used in the preparation of sulfur dyes (see below), however, they are applied by the vatting process using dithionite. Vat Blue 43 is an example of a sulfurized vat dye. To prepare Vat Blue 43, the p-(3-carbazolylamino)phenol intermediate is refluxed with a solution of sodium polysilfide in butanol, then heated with sodium nitrite, distilled to drive off the butanol, and precipitated by the addition of air and salt (Colour Index International, 3.sup.rd Edition, Society of Dyers and Colourists, CD-ROM version, AATCC Box 12215, Research Triangle Park, N.C., p. 4497).
Apart from the reducing agents, other chemicals may be necessary to insure satisfactory dyeing with vat dyes. These chemicals may include caustic soda to maintain a pH of 12-13 to prevent the formation of insoluble enolic acid leuco compound; neutral salts to increase the substantivity of the leuco dye for the fiber; nonionic agents to form complexes with the leuco dyes to improve the levelness of the dyeings (e.g., alkoxylated types) or to partially strip faulty dyeings (e.g., polyvinylpyrrolidone); a wetting agent to emulsify waxes of the material and insure satisfactory penetration of the dye liquor into the material; a sequestering agent to chelate alkaline-earth ions contained in the material and process water (e.g., sodium hexametaphosphate or EDTA); a dispersing agent to prevent the aggregation of undissolved particles; and anionic polymeric inhibitors to prevent pigment migration in the drying operation.
Sulfur dyes are a large class of synthetic dyes obtained by treating aromatic compounds containing nitro and/or amino groups, e.g., aminophenols, with sulfur and/or sodium polysulfide at high temperature in the absence of solvent (baked dyes) or presence of solvent (boiled dyes), such as water or ethanol. In general, sulfur dyes can be described as water-insoluble macromolecules containing sulfur both as an integral part of the chromophore and in attached disulfide bonds between aromatic residues. Sulfur dyes are also water-insoluble and can be applied to a material only in the reduced state.
The most common structural element in the baked sulfur dyes is the benzothiazole group. Most of the baked dyes are yellow, orange, or brown.
The boiled sulfur dyes are blue, green, violet, and black, and most are derivatives of phenylthiazones, phenazones, and phenoxanes.
In the methods of the present invention, the sulfur dye may be any sulfur dye. Sulfur dyes are commercially available in the form of powders, pre-reduced powders, grains, dispersed powders, dispersed pastes, or liquids.
In a preferred embodiment, the sulfur dye is a benzothiazole, phenylthiazone, phenazone, or phenoxane dye, each of which is optionally substituted with one or more mono-, di- or polycyclic aromatic or polycyclic heteroaromatic compounds. Examples of such mono-, di- or polycyclic aromatic or heteroaromatic compounds include, but are not limited to, an acridine, anthracene, azulene, benzene, benzofurane, benzothiazole, benzothiazoline, carboline, carbazole, cinnoline, chromane, chromene, chrysene, fulvene, furan, imidazole, indazole, indene, indole, indoline, indolizine, isothiazole, isoquinoline, isoxazole, naphthalene, naphthylene, naphthylpyridine, oxazole, perylene, phenanthrene, phenazine, phtalizine, pteridine, purine, pyran, pyrazole, pyrene, pyridazine, pyridazone, pyridine, pyrimidine, pyrrole, quinazoline, quinoline, quinoxaline, sulfonyl, thiophene, and triazine, each of which are optionally substituted. The benzothiazole, phenylthiazone, phenazone, or phenoxane dye and the one or more optional mono-, di- or polycyclic aromatic or polycyclic heteroaromatic compound substituents thereof, may optionally be substituted with one or more functional groups or substituents, wherein each functional group or substituent is selected from the group consisting of halogen; sulfo; sulfonato; sulfamnino; sulfanyl; thiol, amino; amido; nitro; azo; imino; carboxy; cyano; formyl; hydroxy; halocarbonyl; carbamoyl; carbamidoyl; phosphonato; phosphonyl; C.sub.1-18 -alkyl; C.sub.1-18 -alkenyl; C.sub.1-18 -alkynyl; C.sub.1-18 -alkoxy; C.sub.1-18 -oxycarbonyl; C.sub.1-18 -oxoalkyl; C.sub.1-18 -alkyl sulfanyl; C.sub.1-18 -alkyl sulfonyl; and C.sub.1-18 -alkyl imino or amino which is substituted with one, two or three C.sub.1-18 -alkyl groups. All C.sub.1-18 -alkyl, C.sub.1-18 -alkenyl and C.sub.1-18 -alkynyl groups may be mono-, di or poly-substituted by any of the proceeding functional groups or substituents. For examples of sulfur dyes, see the Colour Index International, 3.sup.rd Edition, supra.
In a preferred embodiment, the sulfur dye is Sulfur Black, Sulfur Blue, Sulfur Brown, Sulfur Green, Sulfur Orange, Sulfur Violet, or Sulfur Yellow. Examples of these sulfur dyes include, but are not limited to, Sulfur Black 1, Sulfur Black 2, Sulfur Black 4, Sulfur Black 11, Sulfur Blue 9, Sulfur Blue 13, Sulfur Blue 14, Sulfur Brown 1, Sulfur Brown 8, Sulfur Brown 10, Sulfur Brown 52, Sulfur Green 2, Sulfur Green 3, Sulfur Green 7, Sulfur Green 10, Sulfur Green 14, Sulfur Orange 1, Sulfur Red 5, Sulfur Red 6, Sulfur Red 10, Sulfur Violet 1, and Sulfur Yellow 4.
The conversion of an insoluble sulfur dye to a soluble dye generally involves the reduction of the disulfide groups of the sulfur dye. Since the reduction potential of sulfur dyes is -400 mV to -500 mV, milder reducing agents than those used in vat dyeing may be used (see, for example. Alan Johnson (editor), The Theory of Coloration and Textiles, Second Edition, Society of Dyers and Colourists, 1989). Sodium sulfide has been the traditional reducing agent with sulfur dyes, but sodium hydrosulfide is more widely used. Other reducing agents include, but are not limited to, caustic soda/sodium dithionite, sodium carbonate/sodium dithionite, glucose, thioglycol, hydroxyacetone, thiourea dioxide, and cathodic reduction.
The color fastness of sulfur dyes depends greatly on the reduction conditions since over-reduction of the dye may result in low color yields and/or off-shades. The sulfur dyes are very fast to light and washing, but not to chlorine. They are used mainly to dye cotton and other plant fibers in a sodium sulfide bath. A subsequent treatment with metal salts can improve the quality of the dyeing.
The reduction of a sulfur dye may be accomplished using any method known in the art (see, for example, David R. Waring and Goeffrey Hallas (editors), The Chemistry and Application of Dye, Plenum Press, New York, 1990, pp. 287-309; and Henrich Zollinger, Color Chemistry, VCH Publishers, Inc., New York, 1991, pp. 232-236). The sulfur dye is generally dissolved by boiling for several minutes in a reducing solution (e.g., sodium sulfide) or by vatting with caustic soda and sodium dithionite in a similar manner to vat dyes. See, for example, John Shore (editor), Colorants and Auxiliaries, Volume 2, Society of Dyers and Colourists, 1990; and John Shore (editor), Cellulosics Dyeing, Society of Dyers and Colourists, West Yorkshire, England, 1995.
Apart from the reducing agents, other chemicals as described above for vat dyes may be necessary to insure satisfactory dyeing with sulfur dyes. In addition to the chemicals described above, fixative additives may be used to improve color fastness (e.g., epichlorohydrin derivatives).
In the methods of the present invention, the application of a reduced vat and/or sulfur dye(s) to a material generally involves the following steps: (1) dyeing, (2) reduction, (3) penetration, and (4) oxidation. The phrase "dyeing of a material" will also be understood to encompass the printing of a material with such dyes.
In the first step, the dyeing of the material occurs by contacting the dyebath with the material by moving the material through a stationary bath containing dye, by pumping the dye bath through the material, or having both the material and dye liquor mixed together. Examples of the equipment that may be used in these processes are described by Tindall, 1996, Journal of the Textile Association 57: 27-34, and John Shore (editor), Cellulosics Dyeing, Society of Dyers and Colourists, West Yorkshire, England, 1995.
In the second step, the vat and/or sulfur dye applied to the material is chemically reduced using methods known in the art (see, for example, John Shore (editor), Colorants and Auxiliaries, Volume 2, Society of Dyers and Colourists, 1990). Steps one and two can be reversed, in which case the vat and/or sulfur dye is first chemically reduced, and then is contacted with the material.
In the third step, the reduced dye adsorbs onto and diffuses into the material. The substantivity of the reduced dye toward the material can be attributed to the ion-dipole and dispersion forces operating between the dye ion and the material. The rate of penetration is determined by the difflusion coefficient, D, which increases with temperature. At higher temperatures, the material tends to become more flexible increasing the free volume, thereby increasing penetration.
In the fourth step, the reduced dye is fixed or trapped in the fiber by enzymatic oxidation of the reduced dye to its original oxidized insoluble colored form. The enzymatic oxidation system may be added at any point during the dyeing process including simultaneously with the dyeing system. For example, the material containing reduced dye can be dipped or soaked in the enzymatic oxidation system, or the enzymatic oxidation system can be applied to the surface of the material containing reduced dye. Alternatively, the un-dyed material can first be placed in contact with the enzyme component of the enzymatic oxidation system, then placed, sequentially or simultaneously, in contact with the dye and reducing agent, and then, after penetration of the reduced dye into the material, which may be controlled to give a desired effect, the material is exposed to an electron acceptor appropriate for the enzyme used (for example, exposure to air when laccase is used, or to hydrogen peroxide when peroxidase is used). If a chemical mediator (described below) is used, it may be applied separately or simultaneously with the enzyme.
Following washing and drying of the dyed material, the CIELAB values can then be measured using an instrument suited for such purposes. The parameters "L", "a", and "b" are used to quantify color and are well known to persons of ordinary skill in the art of color science. See, for example, Billmeyer and Saltzmnan, Principles of Color Technology, Second Edition, John Wiley & Sons, New York, 1981, page 59 and subsequent.
Following the dyeing of the material according to the methods of the present invention, the dyed material may then be further processed according to standard techniques known in the art, e.g., after-soaping, drying, etc., prior to the material's intended use such as in garments.
There is no standard dyeing process in the art since the procedure will depend on the available equipment, material, amount of material, and actual dye(s). The dyeing process may be batchwise, semi-continuous, or continuous. For examples of various procedures, see John Shore (editor), Cellulosics Dyeing, Society of Dyers and Colourists, West Yorkshire, England, 1995; David R. Waring and Goeffrey Hallas (editors), The Chemistry and Application of Dye, Plenum Press, New York, 1990; Textile Chemist and Colorist 12: 38-39; Perkins, 1991, Textile Chemist and Colorist 23: 23-27; and Tigler, 1980, Textile Chemist and Colorist 6: 43-44.
The material dyed by the methods of the present invention may be a fabric, yarn, fiber, -garment or film. Preferably, the material is made of cotton (or cellulose), diacetate, flax, fur, hide, linen, lyocel, polyacrylic, polyamide (e.g., leather, silk, wool, nylon), polyester, ramie, rayon, triacetate, or viscose.
The dye liquor, which comprises the material, used in the methods of the present invention may have a liquor/material ratio in the range of about 0.5:1 to about 200:1, preferably about 0.6:1 to about 20:1.
The concentration of reduced dye in the dye liquor will depend on the material being dyed, the dye, and the amount of material being dyed. Determining the amount of dye is well within the skilled art. See, for example, John Shore (editor), Cellulosics Dyeing, Society of Dyers and Colourists, West Yorkshire, England, 1995; David R. Waring and Goeffrey Hallas (editors), The Chemistry and Application of Dye, Plenum Press, New York, 1990; and Henrich Zollinger, Color Chemistry, VCH Publishers, Inc., New York, 1991.
The dye adsorption and diff-usion step in a continuous process can be performed at a temperature in the range of about 15.degree. C. to about 55.degree. C., preferably about 15.degree. C. to about 45.degree. C., preferably about 15.degree. C. to about 35.degree. C., more preferably about 15.degree. C. to about 30.degree. C., and most preferably about 15.degree. C. to about 25.degree. C., and at a pH in the range of about 9 to about 13, preferably about 10 to about 13, more preferably about 11 to about 13, and most preferably about 12 to about 13 for a period of about 20 seconds to about 10 minutes, preferably about 25 seconds to about 5 minutes, more preferably about 30 seconds to about 2 minutes, and most preferably about 30 seconds to about 1 minute.
The dye adsorption and diffuision step in a batch process can be performed at a temperature in the range of about 20.degree. C. to about 115.degree. C., preferably about 30.degree. C. to about 100.degree. C., preferably about 40.degree. C. to about 90.degree. C., more preferably about 45.degree. C. to about 80.degree. C., and most preferably about 50.degree. C. to about 80.degree. C., and at a pH in the range of about 9 to about 13, preferably about 10 to about 13, more preferably about 11 to about 13, and most preferably about 12 to about 13 for a period of about 10 minutes to about 90 minutes, preferably about 10 minutes to about 80 minutes, more preferably about 10 minutes to about 70 minutes, and most preferably about 10 minutes to about 60 minutes.
According to the methods of the present invention, the one or more reduced vat dyes and/or one or more reduced sulfur dyes are oxidized to their original oxidized insoluble colored forms with an oxidation system comprising (a) an oxygen source and one or more enzymes exhibiting oxidase activity and/or (b) a hydrogen peroxide source and one or more enzymes exhibiting peroxidase activity. The enzymatic oxidation step also serves to fix the dye to the material.
Enzymes exhibiting oxidase activity are preferably copper oxidases (e.g., blue copper oxidases), which include, but are not limited to, bilirubin oxidase (EC 1.3.3.5), catechol oxidase (EC 1.10.3.1), laccase (EC 1.10.3.2), o-aminophenol oxidase (EC 1.10.3.4), polyphenol oxidase (EC 1.10.3.2), ascorbate oxidase (EC 1.10.3.3), and ceruloplasmin. Enzymes exhibiting peroxidase activity include, but are not limited to, peroxidase (EC 1.11.1.7) and haloperoxidase, e.g., chloro- (EC 1.11.1.10), bromo- (EC 1.11.1) and iodoperoxidase (EC 1.11.1.8). Assays for determining the activity of these enzymes are well known to persons of ordinary skill in the art.
When the one or more enzymes employed in the invention are oxidases, an oxygen source, e.g., air, is used. Oxygen can be supplied by simply aerating the solution containing the material being dyed.
When the one or more enzymes employed in the invention are peroxidases, a hydrogen peroxide source, e.g., hydrogen peroxide itself, is used. The hydrogen peroxide source may be added at the beginning or during the process, e.g., in an amount of 0.001-5 mM, particularly 0.01-1 mM.
One source of hydrogen peroxide includes precursors of hydrogen peroxide, e.g., a perborate or a percarbonate. Another source of hydrogen peroxide includes enzymes which are able to convert molecular oxygen and an organic or inorganic substrate into hydrogen peroxide and the oxidized substrate, respectively. These enzymes produce only low levels of hydrogen peroxide, but they may be employed to great advantage in the methods of the present invention as the presence of peroxidase ensures an efficient utilization of the hydrogen peroxide produced. Examples of enzymes which are capable of producing hydrogen peroxide include, but are not limited to, alcohol oxidase, amine oxidase, amino acid oxidase, cholesterol oxidase, galactose oxidase, glucose oxidase, glutathione oxidase, sulfhydryl oxidase, and urate oxidase.
The laccase(s) may be a plant, microbial, insect, or mammalian laccase.
In a preferred embodiment, the laccase(s) is a plant laccase. For example, the laccase may be a lacquer, mango, mung bean, peach, pine, poplar, prune, sycamore, or tobacco laccase.
In another preferred embodiment, the laccase(s) is an insect laccase. For example, the laccase may be a Bombyx, Calliphora, Diploptera, Drosophila, Lucilia, Manduca, Musca, Oryctes, Papilio, Phorma, Rhodnius, Sarcophaga, Schistocerca, or Tenebrio laccase.
The laccase(s) is preferably a microbial laccase, such as a bacterial or fungal laccase.
In another preferred embodiment, the laccase(s) is a bacterial laccase. For example, the laccase may be an Acetobacter, Acinetobacter, Agrobacterium, Alcaligenes, Arthrobacter, Azospirillum, Azotobacter, Bacillus, Comamonas, Clostridium, Gluconobacter, Halobacterium, Mycobacterium, Rhizobium, Salmonella, Serratia, Streptomyces, E. coli, Pseudomonas, Wolinella, or methylotrophic bacterial laccase.
In a more preferred embodiment, the laccase(s) is an Azospirillum lipoferum laccase.
In another preferred embodiment, the laccase(s) is a fingal laccase. For example, the laccase(s) may be a yeast laccase such as a Candida, Kluyveromyces, Pichia, Saccharomyces, Schizosaccharomyces, or Yarrowia laccase; or a filamentous fungal laccase such as an Acremonium, Agaricus, Antrodiella, Armillaria, Aspergillus, Aureobasidium, Bjerkandera, Botrytis, Cerrena, Chaetomium, Chrysosporium, Collybia, Coprinus, Cryptococcus, Cryphonectria, Curvularia, Cyathus, Daedalea, Filibasidium, Fomes, Fusarium, Geotrichum, Halosarpheia, Humicola, Junghuhnia, Lactarius, Lentinus, Magnaporthe, Monilia, Monocillium, Mucor, Myceliophthora, Neocallimastix, Neurospora, Paecilomyces, Panus, Penicillium, Phanerochaete, Phellinus, Phlebia, Pholiota Piromyces, Pleurotus, Podospora, Pycnoporus, Polyporus (Trametes), Pyricularia, Rhizoctonia, Rigidoporus, Schizophyllum, Sclerotium, Scytalidium, Sordaria, Sporotrichum, Stagonospora, Talaromyces, Thermoascus, Thielavia, Tolypocladium, or Trichoderma laccase.
In a more preferred embodiment, the laccase(s) is a Coprinus cinereus, Humicola brevis var. thermoidea, Humicola brevispora, Humicola grisea var. thermoidea, Humicola insolens, and Humicola lanuginosa (also known as Thermomyces lanuginosus), Myceliophthora thermophila, Myceliophthora vellerea, Polyporus alveolaris, Polyporus arcularius, Polyporus australiensis, Polyporus badius, Polyporus biformis, Polyporus brumalis, Polyporus ciliatus, Polyporus colensoi, Polyporus eucalyptorum, Polyporus meridionalis, Polyporus palustris, Polyporus pinsitus (also known as Trametes villosa), Polyporus rhizophilus, Polyporus rugulosus, Polyporus squamosus, Polyporus tuberaster, Polyporus tumulosus, Polyporus varius, Polyporus versicolor. Polyporus zonatus, Pycnoporus cinabarinus, Rhizoctonis praticola, Rhizoctonia solani, Scytalidium acidophilum, Scytalidium album, Scytalidium aurantiacum, Scytalidium circinatum, Scytalidium flaveobrunneum, Scytalidium hyalinum, Scytalidium indonesiacum, Scytalidium lignicola, Scytalidium thermophilum, Scytalidium uredinicolum, or Torula thermophila laccase. The laccase(s) may also be a modified laccase by at least one amino acid residue in or near the copper sites, wherein the modified oxidase possesses an altered pH and/or specific activity relative to the wild-type oxidase. For example, the modified laccase(s) could be modified in segment (a) of the Type 1 copper site.
The peroxidase(s) may be a plant, microbial, insect, or mammalian peroxidase.
In a preferred embodiment, the peroxidase(s) is a plant peroxidase. For example, the peroxidase may be a horseradish peroxidase.
The peroxidase(s) may be a microbial peroxidase, such as a bacterial or a fungal peroxidase.
In another preferred embodiment, the peroxidase(s) is a bacterial peroxidase. For example, the peroxidase may be a Bacillus, Pseudomonas, Rhodobacter, Rhodomonas, Streptococcus, Streptomyces, or Streptoverticillum peroxidase.
In a more preferred embodiment, the peroxidase(s) is a Bacillus pumilus (ATCC 12905), Bacillus stearothermophilus, Pseudomonas fluorescens (NRRL B-11), Pseudomonas purrocinia (ATCC 15958), Rhodomonas palustri, Rhodobacter sphaeroides, Streptococcus lactis, Streptomyces spheroides (ATTC 23965), Streptomyces thermoviolaceus (IFO 12382), or Streptoverticillum verticillium ssp. verticillium peroxidase.
In another preferred embodiment, the peroxidase(s) is a fungal peroxidase. For example, the peroxidase may be a yeast peroxidase such as a Candida, Kluyveromyces, Pichia, Saccharomyces, Schizosaccharomyces, or Yarrowia peroxidase; or a filamentous fungal peroxidase such as an Aspergillus, Arthromyces, Caldariomyces, Cladosporium, Coprinus, Coriolus, Dreschlera, Embellisia, Fusarium, Humicola, Mucor, Myrothecium, Phanerochaete, Rhizopus, Trametes, Trichoderma, Ulocladium, or Verticillum peroxidase.
In a more preferred embodiment, the peroxidase(s) is an Arthromyces ramosus (FERM P-7754), Caldariomyces fumago, Coprinus cinereus f. microsporus (IFO 8371), Coprinus macrorhizus, Coriolus versicolor (e.g., PR4 28-A), Dreschlera halodes, Embellisia alli, Fusarium oxysporum (DSM 2672), Humicola insolens, Mucor hiemalis, Myrothecium verrucana (IFO 6113), Phanerochaete chrysosporium (e.g., NA-12), Trichoderma reesei, Ulocladium chartarum, Verticillum alboatrum, or Verticillum dahlie peroxidase.
Other potential sources of peroxidases are listed in B. C. Saunders et al., op. cit., pp. 41-43.
Methods for producing enzymes to be used in the methods of the present invention are described in the art, e.g., Applied and Environmental Microbiology 49: 273-278 (1985), Applied Microbiol. Biotechnol. 26: 158-163 (1987), Biotechnology Letters 9: 357-360 (1987), Agric. Biol. Chem. 50: 247 (1986), EP 179 486, EP 200 565, GB 2 167 421, and EP 171 074.
Particularly preferred enzymes are those which are active at a pH in the range of about 2.5 to about 12.0, more preferably about 4 to about 10, and most preferably about 4.0 to about 7.0 or about 7.0 to about 10.0. Such enzymes may be isolated by screening for the relevant enzyme production by alkalophilic microorganisms, e.g., using the 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) assay described in Childs and Bardsley, 1975, Biochem. J. 145: 93-103.
Other preferred enzymes are those which exhibit a good thermostability as well as a good stability towards commonly used dyeing additives such as non-ionic, cationic, or anionic surfactants, chelating agents, salts, polymers, etc.
The enzyme of interest may also be produced by a method comprising cultivating a host cell transformed with a recombinant DNA vector which carries a DNA sequence encoding the enzyme as well as DNA sequences encoding functions permitting the expression of the DNA sequence encoding the enzyme, in a culture medium under conditions conducive for expression of the enzyme and recovering the enzyme from the culture.
A DNA fragment encoding the enzyme may, for instance, be isolated by establishing a cDNA or genomic library of a microorganism producing the enzyme of interest, such as one of the organisms mentioned above, and screening for positive clones by conventional procedures such as by hybridization to nucleic acid probes synthesized on the basis of the full or partial amino acid sequence of the enzyme, by selecting for clones expressing the appropriate enzyme activity, or by selecting for clones producing a protein which is reactive with an antibody against the native enzyme.
Once selected, the DNA sequence may be inserted into a suitable replicable expression vector comprising appropriate promoter, operator and terminator sequences permitting the enzyme to be expressed in a particular host organism.
The resulting expression vector may then be transformed into a suitable host cell, such as a fungal cell, preferred examples of which are species of Aspergillus, most preferably Aspergillus oryzae and Aspergillus niger, and species of Fusarium, most preferably Fusarium venenatum. Fungal cells may be transformed by a process involving protoplast formation and transformation of the protoplasts followed by regeneration of the cell wall in a manner known per se. The use of Aspergillus as a host microorganism is described in EP 238,023. The use of Fusarium as a host microorganism is described in WO 96/00787 and WO 97/08325.
Alternatively, the host organism may be a bacterium, in particular strains of Bacillus, Pseudomonas, Streptomyces, or E. coli. The transformation of bacterial cells may be performed according to conventional methods, e.g., as described in T. Maniatis et al., Molecular Cloning: A Laboratory Manual, Cold Spring Harbor, 1982.
The screening of appropriate DNA sequences and construction of vectors may also be carried out by standard procedures, cf. T. Maniatis et al., op. cit.
The medium used to cultivate the transformed host cells may be any conventional medium suitable for growing the host cells in question. The expressed enzyme may conveniently be secreted into the culture medium and may be recovered therefrom by well-known procedures including separating the cells from the medium by centrifugation or filtration, precipitating proteinaceous components of the medium by means of a salt such as ammonium sulphate, followed by chromatographic procedures such as ion exchange chromatography, affinity chromatography, or the like.
The amount of enzyme(s) used in the oxidation step, especially when a chemical mediator is present, and the conditions employed are critical in the methods of the present invention in order to avoid bleaching of the dye or converting the dye to a different color with the enzymatic oxidation system.
The amount of enzyme(s) used in the oxidization step should be in an amount effective to achieve an efficient diffusion rate such that substantially all of the material (generally greater than about 70%, preferably greater than about 80%, more preferably greater than about 90%, and most preferably greater than about 95%) comes into contact with the enzyme(s). Determining a sufficient amount of the enzyme(s) is well within the skilled art. The amount of enzyme(s) is generally in the range of about 0.001% to about 50%, preferably about 0.01% to about 25%, and more preferably about 0.1% to about 10% enzyme protein of the dry weight of dye.
If the pH of the dye liquor is not compatible with the optimal activity of the enzyme(s), the liquor may need to be pH adjusted particularly before addition of the enzyme(s). The need for pH adjustment may not be necessary, especially if the enzyme(s) has optimal activity compatible with the pH of the liquor.
The enzymatic oxidation step can be performed at a temperature in the range of about 5.degree. C. to about 120.degree. C., preferably about 5.degree. C. to about 80.degree. C., and more preferably about 15.degree. C. to about 70.degree. C., and a pH in the range of about 2.5 to about 12, preferably about 4 to about 10, and more preferably about 4.0 to about 7.0 or about 7.0 to about 10.0 for a period of preferably about 0.1 minute to about 60 minutes, more preferably about 0.1 minute to about 30 minutes, even more preferably about 0.1 minute to about 15 minutes, and most preferably about 0.2 minute to about 5 minutes. Preferably, a temperature and pH near the temperature and pH optima of the enzyme, respectively, are used.
In a preferred embodiment, the enzymatic oxidation system further comprises one or more chemical mediator agents which enhance the activity of the enzyme exhibiting peroxidase activity or the enzyme exhibiting oxidase activity. The term "chemical mediator" is defined herein as a chemical compound which acts as a redox mediator to effectively shuttle electrons between the enzyme exhibiting peroxidase activity or the enzyme exhibiting oxidase activity and the dye. Chemical mediators are also known as enhancers and accelerators in the art.
The chemical mediator may be a phenolic compound, for example, methyl syringate. The chemical mediator may also be an N-hydroxy compound, an N-oxime compound, or an N-oxide compound, for example, N-hydroxybenzotriazole, violuric acid, or N-hydroxyacetanilide. The chemical mediator may also be a phenoxazine/phenathiazine compound, for example, phenathiozine-10-propionate. The chemical mediator may further be 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). Other chemical mediators are well known in the art. For example, the organic chemical compounds disclosed in WO 95/01426 are known to enhance the activity of a laccase. Furthermore, the chemical compounds disclosed in WO 94/12619 and WO 94/12621 are known to enhance the activity of a peroxidase.
The chemical mediator is added to the dye liquor in an amount of about 0.5% to about 100%, preferably about 1% to about 75%, preferably about 1% to about 50%, more preferably about 1% to about 25%, and most preferably about 1% to about 5% dry weight of mediator per dry weight of dye.
When a chemical mediator is included in the oxidation step, the oxidation can be performed at a temperature in the range of about 5.degree. C. to about 120.degree. C., preferably about 5.degree. C. to about 80.degree. C., and more preferably about 15.degree. C. to about 70.degree. C., and a pH in the range of about 2.5 to about 12, preferably about 4 to about 10, and more preferably about 4.0 to about 7.0 or about 7.0 to about 10.0 for a period of preferably about 0.1 minute to about 60 minutes, more preferably about 0.1 minute to about 30 minutes, even more preferably about 0.1 minute to about 15 minutes, and most preferably about 0.2 minutes to about 5 minutes.
In the methods of the present invention, combinations of chemical mediators may be used for oxidizing two or more reduced vat and/or sulfur dyes, particularly where the presence of different reduced dyes may require different oxidases and/or peroxidases with different substrate specificities.
The oxidation system used in the methods of the present invention may further comprise a mono- or divalent ion which includes, but is not limited to, sodium, potassium, calcium and magnesium ions (0 to 3 M, preferably 25 mM to 1 M), a polymer which includes, but is not limited to, polyvinylpyrrolidone, polyvinylalcohol, polyaspartate, polyvinylamide, polyethylene oxide (0-50 g/l, preferably 1-500 mg/l) and a surfactant (10 mg-5 g/l).
Examples of such surfactants are anionic surfactants such as carboxylates, for example, a metal carboxylate of a long chain fatty acid; N-acylsarcosinates; mono or di-esters of phosphoric acid with fatty alcohol ethoxylates or salts of such esters; fatty alcohol sulphates such as sodium dodecyl sulphate, sodium octadecyl sulphate or sodium cetyl sulphate; ethoxylated fatty alcohol sulphates; ethoxylated alkylphenol sulphates; lignin sulphonates; petroleum sulphonates; alkyl aryl sulphonates such as alkyl-benzene sulphonates or lower alkylnaphthalene sulphonates, e.g., butyl-naphthalene sulphonate; salts or sulphonated naphthalene-formaldehyde condensates; salts of sulphonated phenol-formaldehyde condensates; or more complex sulphonates such as amide sulphonates, e.g., the sulphonated condensation product of oleic acid and N-methyl taurine or the dialkyl sulphosuccinates, e.g., the sodium sulphonate or dioctyl succinate. Further examples of such surfactants are non-ionic surfactants such as condensation products of fatty acid esters, fatty alcohols, fatty acid amides or fatty- alkyl- or alkenyl-substituted phenols with ethylene oxide, block copolymers of ethylene oxide and propylene oxide, acetylenic glycols such as 2,4,7,9-tetraethyl-5-decyn-4,7-diol, or ethoxylated acetylenic glycols. Further examples of such surfactants are cationic surfactants such as aliphatic mono-, di-, or polyamines such as acetates, naphthenates or oleates; oxygen-containing amines such as an amine oxide of polyoxyethylene alkylamine; amide-linked amines prepared by the condensation of a carboxylic acid with a di- or polyamine; or quaternary ammonium salts.
The present invention also relates to dyed materials obtained by the methods of the present invention. The material may be a fabric, yam, fiber, garment or film made of cotton, diacetate, flax, fur, hide, linen, lyocel, polyacrylic, polyamide, polyester, ramie, rayon, triacetate, or viscose.
The invention is further illustrated by the following non-limiting examples.
EXAMPLES
Materials
Chemicals used as buffers and substrates were commercial products of at least reagent grade. Vat Blue 43 (CI 53630), Vat Orange 7 (CI 71105), and Vat Red 13 (CI 70320) were obtained from C. H. Patrick & Co., Greenville, S.C. Vat Blue 1 (C.I. 773000, Indigo Rein) was obtained from BASF, Charlotte, N.C. Vat Green 3 (CI 69500) and Vat Yellow 2 (CI 67300) were obtained from Clariant Corp., Charlotte, N.C. Vat Orange 2 (CI 59705) was obtained from BASF Corp., Charlotte, N.C. Sulfur Black 1 (CI 53185) was obtained from Aakash Chemicals & Dye-Stuffs, Inc., Glendale Heights, Ill. The structures of Indigo, Vat Blue 1, Vat Blue 43, Vat Orange 2, Vat Orange 7, Vat Red 13, Vat Green 3, Vat Yellow 2, and Sulfur Black 1 are shown in FIG. 1.
Example 1
Vat Blue 43 Reduction and Re-oxidation with Laccase
Vat Blue 43 at a 0.01% level was reduced with sodium dithionite in Britton & Robinson (B&R) pH 7 buffer at 20.degree. C. for 1 hour. After the reduction, laccase was added to start the re-oxidation. Both reactions were monitored on a Shimadzu UV160U spectrophotometer in a 1-cm quartz cuvette. Methyl syringate (MS), 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and phenathiozine-10-propionate (PPT) were tested as chemical mediators. Due to the instability of the sodium dithionite stock solution (0.5 M), the actual initial sodium dithionite concentration in the solution was estimated from the reduction extent of the dye. The re-oxidation was studied in solutions in which no excess sodium dithionite was present.
Diluted in either deionized water or B&R buffer, Vat Blue 43 yielded a spectrum with maximal absorbance wavelengths (.lambda..sub.max) at 626 and 289 nm. As measured at 626 nm, the absorbance (A) of Vat Blue 43 obeyed Beer's law (A .varies.[Vat Blue 43]) in the testing range of 0.0006-0.06% Vat Blue 43. The reduction of Vat Blue 43 by sodium dithionite led to the bleaching of its blue color and the decrease of A.sub.626 and the appearance of a new .lambda..sub.max at 614 nm (with pseudo-isosbestic points at 411 and 317 nm). The reduced (leuco) Vat Blue 43 had an A.sub.626 equal to 40% of the initial A.sub.626 of the "native" Vat Blue 43. The time profile of .DELTA.A.sub.626 was of hyperbolic type and, as shown in FIG. 2, the initial reduction rate was proportional to the initial concentration of sodium dithionite.
Purified recombinant Myceliophthora thermophila laccase (rMtL) was obtained as described in WO 95/33836. Laccase activity was determined from the oxidation of syringaldazine under aerobic conditions. The violet color produced was measured spectrophotometrically at 530 nm. The analytical conditions were 19 .mu.M syringaldazine, 23.2 mM acetate buffer, pH 5.5, 30.degree. C., and 1 minute reaction time. One laccase unit (LACU) is the amount of laccase that catalyzes the conversion of 1 micromole of syringaldazine per minute under these conditions.
Upon the addition of Myceliophthora thermophila laccase, reduced Vat Blue 43 was re-oxidized as shown by the appearance of blue color and the increase of A.sub.626. The time profile of .DELTA.A.sub.626 was of hyperbolic type and as shown in FIG. 3, the initial re-oxidation rate was proportional to the initial concentration of reduced Vat Blue 43 as well as Myceliophthora thermophila laccase. The spectrum of the re-oxidized Vat Blue 43 was similar to the initial spectrum of the native Vat Blue 43, except that the absorbance for the former was about 80% of that for the latter. No significant re-oxidation of reduced Vat Blue 43 was observed when the Myceliophthora thermophila laccase-storing buffer (10 mM Tris-Cl pH 7.5) was added. The presence of 60 .mu.M PPT increased the oxidation rate of 20 nM Myceliophthora thermophila laccase (0.06 LACU) by two-fold.
Example 2
Vat Orange 7 Reduction and Re-oxidation with Laccase or Peroxidase
Vat Orange 7 was reduced with sodium dithionite using the same procedure described in Example 1 for Vat Blue 43.
Diluted in either deionized H.sub.2 O or B&R buffer, Vat Orange 7 yielded a spectrum with .lambda..sub.max at 540, 500, 457, 434, and 303 nm. The reduction of Vat Orange 7 by sodium dithionite transformed it from orange to a greenish black color. The reduced Vat Orange 7 had .lambda..sub.max at 622, 572, 540, 502, 447, and 419 nm (with pseudo-isosbestic points at 566, 458, and 376 nm). The time courses of A.sub.540 (decrease) and A.sub.622 (increase) yielded the same kinetic characteristics. The reduced Vat Orange 7 had an A.sub.540 equal to 49% of the initial A.sub.540 of Vat Orange 7. As shown in FIG. 4, the initial reduction rate was proportional to the initial concentration of sodium dithionite.
Purified recombinant Coprinus cinereus peroxidase was obtained as described in WO 97/08325. One peroxidase unit (POXU) is defined as the amount of enzyme that catalyzes the conversion of 1 micromole of hydrogen peroxide per minute under the following conditions: 0.88 mM hydrogen peroxide, 1.67 mM 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate), 0.1 M phosphate buffer (containing Triton X405 at 1.5 g per liter), pH 7.0, incubated at 30.degree. C., photometrically followed at 418 nm (extinction coefficient of ABTS is set to 3.6 l/mmol*mm).
Upon the addition of 25-90 nM Coprinus cinereus peroxidase and 5.3 mM hydrogen peroxide, reduced Vat Orange 7 was re-oxidized by the appearance of orange color and the increase of A.sub.540. The time profile measured at A.sub.540 was of hyperbolic type as shown in FIG. 5 where the initial re-oxidation rate was proportional to the initial concentration of Coprinus cinereus peroxidase. The spectrum of the re-oxidized Vat Orange 7 was similar to the spectrum of Vat Orange 7, except that the absorbance at 540 nm for the re-oxidized Vat Orange 7 was about 80% of that for Vat Orange 7. Reduced Vat Orange 7 could be re-oxidized by hydrogen peroxide, but the presence of Coprinus cinereus peroxidase accelerated the reaction. With 94 nM Coprinus cinereus peroxidase (10 POXU per ml), the initial re-oxidation rate of 0.01% reduced Vat Orange 7 by 5.3 mM hydrogen peroxide was enhanced 10-fold. The presence of PPT further facilitated the reaction. The addition of 0.6 mM PPT led to a 4-fold increase on the initial rate for the re-oxidation of 0.01% reduced Vat Orange 7 by 5.3 mM hydrogen peroxide and 24 nM Coprinus cinereus peroxidase (2.5 POXU per ml).
Myceliophthora thermophila laccase (2.4 .mu.M, 7.2 LACU per ml) in the presence of ABTS (13 .mu.M) also re-oxidized reduced Vat Orange 7. However, the Coprinus cinereus peroxidase with hydrogen peroxide system was more efficient as an oxidation catalyst than the Myceliophthora thermophila laccase/O.sub.2 /ABTS system. The initial re-oxidation rate with 2.4 .mu.M Myceliophthora thermophila laccase and 13 .mu.M ABTS (and 0.28 mM dissolved O.sub.2) was slightly lower than that with 94 nM Coprinus cinereus peroxidase and 5.3 mM hydrogen 25 peroxide.
Example 3
Indigo Reduction and Re-oxidation with Laccase
Swatches (1.times.1 cm) of indigo dyed desized denim cloth (Swift Textiles, France SA, Paris, France) were immersed in 1.3 ml of 0.1 M sodium hydroxide pH 12 containing 0.1 M sodium dithionite. After 10 minutes of vortexing, the blue denim cloth turned yellow in color, indicating the reduction of indigo into leuco indigo. The denim cloth swatches with leuco indigo was quickly transferred into capped 1.7-ml centrifuge tubes containing 1.3 ml of either (a) water; (b) 0.1 mM Tris pH 7.8; (c) 0.1 .mu.M Myceliophthora thermophila laccase in 0.1 mM Tris pH 7.8 (0.3 LACU per ml); (d) 0.1 .mu.M Myceliophthora thermophila laccase and 0.1 mM MS in 0.1 mM Tris pH 7.8; or (e) 0.1 mM MS in 0.1 mM Tris, pH 7.8. The tubes were vortexed for 38 minutes. After a 5 second exposure to air, the tubes were vortexed for another 10 minutes.
The leuco-indigo swatches immersed in 0.1 .mu.M Myceliophthora thermophila laccase and 0.1 mM MS in 0.1 mM Tris pH 7.8 turned from yellow to blue, showing the re-oxidation of leuco-indigo into indigo. There was no color change in the same time frame when either Myceliophthora thermophila laccase or MS was absent.
Example 4
Reduction and Re-oxidation of Vat Green 3, Vat Orange 2, Vat Red 13, and Vat Yellow 2 on Cotton Fabric with Laccase
The ability of laccase to re-oxidize reduced vat dyes impregnated on a fabric was examined using cotton fabric, style 400M, lot 9234, obtained from Testfabrics Inc. (West Pittston, Pa.), and recombinant Myceliophthora thermophila laccase obtained as described in Example 1. Vat Green 3, Vat Orange 2, Vat Red 13, and Vat Yellow 2 were used to dye the fabric since it was visually easy to follow re-oxidation, of the dyes due to the significant changes in color.
Separate pieces of the cotton fabric (1 inch.times.1 inch) were dyed with each of the vat dyes above using the following dyeing procedure. A 4% dye liquor (o.w.f.) was prepared and chemically reduced ("vatted") with 0.0431 M sodium dithionite and 0.0875 M sodium hydroxide for 10 minutes at 50-60.degree. C. The liquor ratio was in the range 1:75 to 1:100. After dyeing, the swatches were rinsed in water, oxidized in air, acidified in acetic acid (pH 2-3), rinsed in water, and soaped for 5 minutes at boil in 2 g of AATCC Standard Detergent (AATCC, Durham, N.C.) per liter and in accordance with the most preferred method described in the Colour Index International, 3rd. Ed. (CD-ROM version, AATCC, Durham, N.C).
The 8 swatches for each color were reduced in a solution containing 0.09 M sodium hydroxide and 0.043 M sodium dithionite for 10 minutes at 40.degree. C.
Then the re-oxidation of the reduced dyes on the swatches was evaluated using the following four solutions (each 26 ml in volume):
[A] Water
[B] B&R pH 7.8 buffer
[C] B&R pH 7.8 buffer with 0.1 .mu.M Myceliophthora thermophila laccase
[D] B&R pH 7.8 buffer with 0.1 .mu.M Myceliophthora thermophila laccase and 100 .mu.M methylsyringate.
The stock Myceliophthora thermophila laccase was diluted in water.
The reduced dye/fabric swatches were transferred to solutions [A] to [D], two swatches in each solution. After 15-30 seconds one of the swatches from each solution was placed on a glass plate to be re-oxidized by air. The rate of re-oxidation in solution and in air was judged visually.
For each dye, the rate of re-oxidation in solutions [A] to [D] was ranked, using the following notation:
A.sub.VG3 >C.sub.VG3 >B.sub.VG3 >>D.sub.VG3
where, for example, the re-oxidation of Vat Green 3 was faster in solution [A] than in solution [C] than in solution [B], and much faster than in solution [D].
The re-oxidation in air took place at approximately the samne rate for all four vat dyes, independent of the previous treatment.
The rankings listed below therefore all relate to re-oxidation of reduced dye in solution: ##EQU1##
Re-oxdation in B&R buffer in the presence of Myceliophthora thermophila laccase at pH 7.8 was faster for all four vat dyes ([C]>[B]). In some cases re-oxidation in high pH (pH 9.4) water (without Myceliophthora thermophila laccase) appeared to be faster than in B&R buffer (pH 8) with Myceliophthora thermophila laccase.
The re-oxidation of reduced Vat Red 13 and Vat Orange 2 on cotton fabric in water was also investigated using the samne procedures described above except one swatch for each dye was transferred to each of the following solutions:
[E] Water (20 ml)
[F] Water with 0.1 .mu.M Myceliophthora thermophila laccase (total volume: 20 ml)
[G] Water with 1.0 .mu.M Myceliophthora thermophila laccase (total volume: 20 ml)
The rate of re-oxidation was also judged visually where the rankings listed below were obtained: ##EQU2##
The pH of solutions [E], [F] and [G] was measured after re-oxidation of the dye, and the Myceliophthora thermophila laccase solution was to some extent able to buffer pH, since PH[E]=9.2 and pH[F]=pH[G]=8.8.
The overall results showed that the vat dyes tested were all substrates for Myceliophthora thermophila laccase at pH 7.8, and Myceliophthora thermophila laccase was able to access the dye in/on the fiber, and thus increase the rate of re-oxidation.
Example 5
The Re-oxidation of Vat Yellow 2 and Vat Red 13 in a Pad-Steamer
The re-oxidation of vat dyes by a laccase in a pad-steamer was investigated using Vat Yellow 2 and Vat Red 13 as dyes and recombinant Myceliophthora thermophila laccase prepared as described in Example 1. The test fabrics were lightweight (.about.100 g/m.sup.2) cotton TF400M fabric (Testfabrics Inc., West Pittston, Pa.) and heavyweight (.about.230 g/m.sup.2) cotton TF428 fabric (Testfabrics Inc., West Pittston, Pa.), additionally desized, scoured, and bleached. The technology of pad-steam dyeing is described in John Shore (editor), Cellulosics Dyeing, Society of Dyers and Colourists, West Yorkshire, England, 1995.
A 4% stock dye solution was prepared by dissolving 40 g of Vat Yellow 2 or Vat Red 13 in 1000 ml of deionized water with 0.5% w/w Tergitol-15-S-12 (Union Carbide, Danbury, Conn.).
Three pieces of cotton TF400M fabric or cotton TF428 fabric were respectively marked P (for successive oxidation with Peroxide), C (for Control, oxidation with buffer only) and E (for successive oxidation with Enzyme), sewn together, and padded with Vat Yellow 2 using a Mathis 2-Bowl Vertical Laboratory Padder, Type VFM (Werner Mathis AG, CH-8156 Oberhasli/Zurich, Switzerland) according to the manufacturer's instructions. The amount of stock dye solution applied to the fabric during padding was monitored as percent wet pick up (% WPU). The WPUs obtained are shown in Table 1.
TABLE 1______________________________________Impregnation with Vat Yellow 2Impregnation with Vat Yellow 2 at 0.7 bar Weight before Weight afterSample padding (g) padding (g) % WPU______________________________________TF400M 54.52 110.95 103.5TF428 125.21 288.70 130.6______________________________________
Three pieces of cotton TF400M fabric or cotton TF428 fabric were respectively marked P (for Peroxide), C (for Control) and E (for Enzyme) and padded separately with Vat Red 13. The WPUs obtained are shown in Tables 2 and 3.
TABLE 2______________________________________Impregnation with Vat Red 13, TF400MImpregnation of TF400M at 0.7 bar Weight before Weight afterSample padding (g) padding (g) % WPU______________________________________P(eroxide) 16.64 34.81 109.0C(ontrol) 16.89 33.88 100.6E(enzyme) 16.28 34.72 113.3______________________________________
TABLE 3______________________________________Impregnation with Vat Red 13, TF428Impregnation of TF428 at 0.7 bar Weight before Weight afterSample padding (g) padding (g) % WPU______________________________________P(eroxide) 44.18 98.21 122.3C(ontrol) 42.22 94.61 124.1E(enzyme) 41.08 96.22 134.2______________________________________
Chemical reduction of the dye impregnated fabrics was performed on a Mathis Pad Steam Range, Type PSA-HTF 350 mm 17796 (Werner Mathis USA, Inc., Concord, N.C.), which included a padding trough and pad mangle, steam box, air trap, and four wash boxes. The fabrics were padded with a solution of 20 g of sodium dithionite and 80 ml of 27% sodium hydroxide per liter of reduction bath at 1.5 bar to obtain approximately 100% WPU for both fabrics. The fabrics were then steamed for one minute at 100.degree. C. under 100% relative humidity (RH) at a fabric speed of 8 meters per minute on the Mathis Pad Steam Range ("pad-steamer") according to the manufacturer's instructions.
Vat Yellow 2 reduced to a blue color on both types of fabric. The color change for Vat Red 13 upon reduction was not as significant as that of Vat Yellow 2, suggesting partial reduction of the dye.
The two dyes were re-oxidized at three different conditions:
1) B&R pH 7 buffer with 0.25% w/w H.sub.2 O.sub.2 at 50.degree. C. for 1 minute
2) B&R pH 7 buffer at 50.degree. C. for 1 minute
3) B&R pH 7 buffer plus 8.3 mg of Myceliophthora thermophila laccase per liter at 50.degree. C. for 1 minute
For (1) 60 ml of a stabilized 50% H.sub.2 O.sub.2 solution was added to 12 liters of B&R buffer immediately before the fabric was passed through a wash box in the pad steamer according to the manufacturer's instructions. For (3) 32 ml (100 mg) of Myceliophthora thermophila laccase was added to 12 liters of B&R buffer immediately before the fabric entered the wash box in the pad steamer. The pH in the oxidation bath was pH 7.0 and time through the bath was 1 minute.
The pH and temperature conditions for re-oxidation of the two vat dyes were based on optimal conditions for the Myceliophthora thermophila laccase.
Soaping
Sodium dodecyl sulfate (SDS) was used for the soaping step. A 150 ml volume of an 80 g of SDS per liter stock solution was added to wash box 2 in the pad-steamer containing 12 liters of water yielding a final concentration of 1 g of SDS per liter.
Soaping took place near the boiling point for approximately 1 minute. During soaping the isolated molecules of vat pigments reorient and associate into a more crystalline form, often producing a significantly different shade along with improved fastness to light and washing. Soaping should also remove any remaining leuco dye and surface dye.
The fabrics were finally passed through a hot rinse (1 minute at 80.degree. C.) and a cold rinse (1 minute at 20.degree. C.) in wash boxes 3 and 4 of the pad-steamer according to the manufacturer's instructions. All dyed fabrics were air dried overnight before measuring K/S values, wash fastness, rub fastness and light fastness.
Evaluation of color fastness
Upon dyeing, the color and color fastness properties of the dyed fabrics were evaluated. The parameters "L", "a", and "b" and K/S were used to quantify color and color strength and are well known to persons of ordinary skill in the art of color science. See, for example, Billmeyer and Saltzman, Principles of Color Technology, Second Edition, John Wiley & Sons, New York, 1981, pages 59, 63, and 183. Color fastness is an important parameter for evaluation of dyed textiles and there are many standard methods known in the art for evaluating color fastness properties (see e.g. AATCC Technical Manual, Vol. 71, American Association of Textile Chemists and Colorists, Research Triangle Park, N.C., 1996). Color fastness was evaluated with respect to wash fastness, light fastness, and crock fastness as described below.
Wash fastness evaluation (W).
The AATCC Color Fastness to Laundering Test Method 61-2A (1989) was followed. CIEL*a*b* measurements were made on the original dyed and then washed samples using a Macbeth ColorEye 7000 Spectrophotometer (Macbeth, New Windsor, N.Y.), set with large area view, 10.degree. observer, D.sub.65 illuminant, and average of two measurements, according to the manufacturer's instructions. (See, for example, Billmeyer and Saltzman, Principles of Color Technology, Second Edition, John Wiley & Sons, New York, 1981, page 63, for an explanation of this color coordinate system).
A gray scale rating was assigned based on the value of the CIEL*a*b* total color difference (.DELTA.E*=(.DELTA.L*+.DELTA.a*+.DELTA.b*).sup.0.5) between the dyed and the washed samples (AATCC Gray Scale Ranking Table, AATCC, Research Triangle Park, N.C., see also Table 22).
Light fastness evaluation.
Light fastness (L) was measured following the AATCC Light Fastness Test Method 16 (1993), Option E. Dyed swatches (4 cm.times.4 cm) were stapled to the black side of a Fade-O-Meter Test Mask No. SL-8A (Atlas Electric Devices Co., Chicago, Ill., Part No. 12-7123-01). The mask was placed in a Suntest CPS+(Slaughter Machinery Company, Lancaster, S.C.) and exposed to a Xenon light source at an irradiance of 756 W/m.sup.2 for 20 hours according to the manufacturer's instructions.
.DELTA.E* and gray scale ratings were generated as described above, except only single measurements were made on the exposed fabric face.
Crock fastness evaluation.
The AATCC Color Fastness to Crocking Test Method 8-1989 was followed for dry crock (DC) and wet (WC) crock fastness.
Wet AATCC crock cloth squares were prepared by pressing each water-saturated crock cloth between AATCC blotting paper under an 18 g weight for 5 seconds to yield approximately 65.+-.5% moisture.
A visual rating (5=best) was assigned by three separate observers using the AATCC Chromatic Transference Scale (AATCC, Research Triangle Park, N.C.) while viewing the samples in a Macbeth SpectraLight II light box (Macbeth, Newburgh, N.Y.) under daylight. The average rating was determined.
All data were analyzed using statistical techniques available through SAS JMP Version 3.2 software (SAS Institute, Inc., Cary, N.C.) in two steps: (1) Shapiro-Wilk W test for normality was applied at a 5% level. (2) Tukey-Kramers comparison of all pairs was applied.
For wash and light fastness, the visual gray scale (GS) data were preferred for comparison because GS is the industry standard. Where the GS data failed to meet the demand for normality, the .DELTA.E* (or dE) values were analyzed instead (given that their distribution was normal).
The results of the effect of Myceliophthora thermophila laccase on the four parameters (K/S, wash fastness, light fastness and crock fastness) are shown below in Tables 4-7.
TABLE 4______________________________________Statistical analysis of Vat Yellow 2/TF400M dataVAT YELLOW 2 ON TF400M TEST.fwdarw. Shapiro-Wilk Tukey-KramerPARA- W test for comparison ofMETER.dwnarw. normality all pairs Comments______________________________________K/S 420 nM Failed No significant Comparison of all differences pairs conducted in spite of nonnormality, to get an indication for this important parameter.dE WASH Passed No significant -- differencesGREY SCALE Failed -- dE Wash analyzedWASH insteaddE LIGHT Passed No significant -- differencesGRAY SCALE Failed -- dE Light analyzedLIGHT insteadDRY CROCK Failed -- Data indicates no significant differencesWET CROCK Failed -- Data indicates no significant differences______________________________________
TABLE 5______________________________________Statistical analysis of Vat Yellow 2/TF428 dataVAT YELLOW 2 ON TF428 TEST.fwdarw. Shapiro-Wilk Tukey-KramerMEASURE- W test for comparison ofMENT.dwnarw. normality all pairs Comments______________________________________K/S 420 nM Passed Peroxide -- significant better than Enzyme and ControldE WASH Passed No significant -- differencesGRAY SCALE Failed -- dE Wash analyzedWASH insteaddE LIGHT Passed Peroxide -- significantly better than Enzyme and ControlGRAY SCALE Failed -- dE Light analyzedLIGHT insteadDRY CROCK Failed -- Data indicates no significant differencesWET CROCK Passed Peroxide and See discussion Control below significantly better than Enzyme______________________________________
TABLE 6______________________________________Statistical analysis of Vat Red 13/TF400M dataVAT RED 13 ON TF400M TEST.fwdarw. Shapiro-Wilk Tukey-KramerMEASURE- W test for comparison ofMENT.dwnarw. normality all pairs Comments______________________________________K/S 540 nM Passed Enzyme and -- Peroxide significant better than ControldE WASH Passed No significant differencesGRAY SCALE Failed -- dE Wash analyzedWASH insteaddE LIGHT Passed No significant -- differencesGRAY SCALE Failed -- dE Light analyzedLIGHT insteadDRY CROCK Passed No significant -- differencesWET CROCK Passed No significant -- differences______________________________________
TABLE 7______________________________________Statistical analysis of Vat Red 13/TF428 dataVAT RED 13 ON TF428 TEST.fwdarw. Shapiro-Wilk Tukey-KramerMEASURE- W test for comparison ofMENT.dwnarw. normality all pairs Comments______________________________________K/S 540 nM Passed Enzyme -- significantly better than Control and PeroxideGRAY SCALE Passed No significant --WASH differencesdE Wash Passed Enzyme -- significantly better than peroxide and controldE LIGHT Passed No significant -- differencesGRAY SCALE Failed -- dE Light analyzedLIGHT insteadDRY CROCK Passed Peroxide -- significantly better than Enzyme and ControlWET CROCK Passed Peroxide No significant significantly differences between better Enzyme/Control than Control and Enzyme/Peroxide______________________________________
K/S is a measure of color strength on fabric where a higher K/S corresponds to a darker dyed fabric. K/S was measured at the .lambda..sub.MAX for each dye, i.e., 420 nm for Vat Yellow 2, and 540 nrm for Vat Red 13.
For Vat Yellow 2, no difference in K/S values for the three treatments on the cotton TF400M fabric was observed. On the cotton TF428 fabric, which is a thicker fabric, peroxide performed significantly better than the Myceliophthora thermophila laccase and the control.
The difference observed between the two types of fabric may be that Vat Yellow 2 is re-oxidized by air on the thin fabric by the time it reaches the oxidation bath. However, on the thick fabric, oxygen from the air would not have enough time to diffuse into the fabric and oxidize the dye. Therefore, an effect of peroxide on the thick dye was seen. These results suggest that re-oxidation of Vat Yellow 2 by the Myceliophthora thermophila laccase occurred at too low a rate to be detectable under the conditions tested.
For Vat Red 13, a distinct effect of the Myceliophthora thermophila laccase on both fabrics was observed. On the TF400M fabric, the laccase and peroxide performed equally well, and significantly better than the control. On the TF428 fabric, the laccase treatment resulted in a significantly higher K/S value compared to the peroxide and control treatments. No effect of peroxide was seen.
In summary the results indicated that the Myceliophthora thermophila laccase had a significant effect on the K/S values for Vat Red 13, where it performed (at least) as good as peroxide. For Vat Yellow 2, peroxide was significantly better than the Myceliophthora thermophila laccase (and the control) on the thick fabric (TF428), whereas none of the treatments had any significant effect on the thin fabric (TF400M).
Wash fastness and light fastness.
Wash fastness for Vat Red 13 on the cotton TF428 fabric treated with the Myceliophthora thermophila laccase was significantly better when the dE wash values were compared. The difference disappeared when the GS wash ratings were compared because the same GS wash rating can cover a relatively large span of dE wash values as shown below in the ATCC Gray Scale Ranking Table (Table 8).
TABLE 8______________________________________AATCC Gray Scale Ranking TableConversion of dE values to Gray Scale Rating______________________________________Delta 0 0.4 1.25 2.1 2.95 4.1 5.8 8.2 11.6 13.6(dE)Gray 5 4-5 4 3-4 3 2-3 2 1-2 1 <1Scale(GS)______________________________________
For Vat Yellow 2 on the cotton TF428 fabric, peroxide performed significantly better than the the Myceliophthora thermophila laccase and control.
Crock fastness.
With respect to crock fastness, the results indicated a tendency that peroxide performed better than the Myceliophthora thermophila laccase. For Vat Yellow 2 on the cotton TF428 fabric, both peroxide and the control performed significantly better than the Myceliophthora thermophila laccase in the wet crock test. For Vat Red 13 on the cotton TF428 fabric, peroxide increased dry crock fastness significantly compared to the control, whereas laccase performed "in between" without showing significant differences compared to peroxide and the control.
These results suggested that more dye is bound to the surface of the fabric when re-oxidizing with the Myceliophthora thermophila laccase than with peroxide.
The overall results can be summarized as follows:
Myceliophthora thermophila laccase had a significant effect on the K/S values for Vat Red 13, where it performed (at least) as good as peroxide. For Vat Yellow 2, peroxide was significantly better than the Myceliophthora thermophila laccase (and control) on the thick fabric (TF428), whereas none of the treatments had any significant effect on the thin fabric (TF400M).
Wash fastness for Vat Red 13 on the cotton TF428 fabric treated with the Myceliophthora thermophila laccase was significantly better when the dE Wash values were compared. The difference disappeared when the GS wash figures were compared because the same GS wash figure can cover a relatively large span of dE wash values.
Light fastness for Vat Yellow 2 on cotton TF428 fabric was significantly better when treated with peroxide.
With respect to crock fastness the tendency was that peroxide performed better than the Myceliophthora thermophila laccase.
Example 6
Effect of pre-treating fabric with Myceliophthora thermophila laccase
Cotton TF428 fabric (desized, scoured, and bleached) was pretreated with recombinant Myceliophthora thermophila laccase solution (Example 1) and then dyed with Vat Blue 1 to determine the effect on depth of color on the fabric when the fabric was pretreated with the laccase.
A Vat Blue 1 dye liquor was prepared by suspending 2 g of Vat Blue 1 in 100 ml of water at 50.degree. C., followed by 4 g of sodium hydroxide and 6 g of sodium dithionite. After 10 minute "vatting," the suspension was transferred to 900 ml of water containing 1 g of sodium hydroxide, 2 g of sodium dithionite, and 1 g of the penetration agent, Primasol FP (BASF, Charlotte, N.C.), to prepare the dye liquor.
Fabric swatches (4 in..times.6 in.) were pretreated by immersion in 5 g of Tergitol 15-S-12 as wetting agent for 15-20 minutes with either no laccase or 25 mg of Myceliophthora thermophila laccase per liter.
Swatches of the laccase pretreated and untreated fabric was then immersed in the dye liquor for 15 seconds (called a "dip"), squeezed to 100% WPU under 1.5 bar of pressure, then oxidized in air for 2 minutes. This procedure was repeated either two or five times. After the last dip, the swatches were left to dry at room temperature overnight, and then were soaped separately for four minutes in warm water (70.degree. C.) containing 2 g of AATCC Standard detergent per liter. After soaping the swatches were rinsed in water, and dried at room temperature overnight. Four replicates of all swatches were prepared.
K/S (color strength) was measured on the dried dyed swatches using a Macbeth ColorEye 7000 Spectrophotometer set with large area view, D.sub.65 (daylight) illuminant, and 10.degree. observer according to the manufacturer's instructions. A total of six measurements were made, three on each side of the swatch.
The K/S value as a function of the number of dips and laccase treatment is shown in Table 9. A higher K/S (darker color) was obtained for laccase-treated fabric than for the controls.
TABLE 9______________________________________K/S for Laccase Treated and Control Indigo Dyed Fabrics Number of DipsLaccase Dose (mg/L) 2 5______________________________________ 0 7.13 12.725 9.75 16.4______________________________________
Example 7
Oxidation of Reduced (leuco) Sulfur Black 1 with Myceliophthora thermophila Laccase
A stock solution of Sulfur Black 1 was prepared by dissolving the dye in deionized water to a concentration of 1% w/v. Sulfur Black 1 (at 10-100 ppm) was reduced with sodium dithionite in water at 23.degree. C. using approximately an equal molar amount. Due to the instability of sodium dithionite stock solution (0.5 M), the actual initial concentration of sodium dithionite in solution was estimated from the reduction extent of Sulfur Black 1. The re-oxidation was studied in solutions in which no excess sodium dithionite was present. Both the reduction and the following re-oxidation of Sulfur Black 1 were monitored on a Shimadzu UV160U spectrophotometer in a 1-cm quartz cuvette.
In water, Sulfur Black 1 has an UV-visible spectrum with a maximal absorbance wavelength (.lambda..sub.max) at 627 mn, whose absorption followed Beer's law (A .varies.[Sulfur Black 1]) in the range of 10-100 ppm Sulfur Black 1. For 100 ppm Sulfur Black 1, an A.sub.627 of 1.24.+-.0.05 was observed. The reduction of Sulfur Black 1 by sodium dithionite led to the bleaching of its black color. At low sodium dithionite concentrations, the reduction resulted in a decrease of A.sub.627 and the appearance of a new .lambda..sub.max at 753 nm (with pseudoisosbestic points at 565, 713 and 793 nm). As the concentration of sodium dithionite was increased, the pseudo-isosbestic points disappeared and a new .lambda..sub.max at 593 nm emerged. The band at 593 nm disappeared too when the concentration of sodium dithionite was further increased. The final reduced (leuco) Sulfur Black 1 had a spectrum whose residual absorption at .lambda.=600 nm was 3% of the initial A.sub.627 of the "native" Sulfur Black 1.
Upon depletion of sodium dithionite, reduced Sulfur Black 1 was re-oxidized by air as shown by the appearance of black color and the increase of A.sub.627. The time profile of A.sub.627 had two phases (FIG. 6). The initial phase was faster (.about.8.times.) and had a .DELTA.A.sub.627 equal to .about.30% of the final .DELTA.A.sub.627. For 12.5, 25, 50, and 100 ppm leuco Sulfur Black 1, the re-oxidation rate was proportional to the concentration of leuco Sulfur Black 1 for both phases. For 50 ppm leuco Sulfur Black 1, the initial re-oxidation rate was .about.0.1 .DELTA.A/min and the half-life (t.sub.1/2) was .about.0.8 min. The spectrum of the re-oxidized Sulfur Black 1 was similar to the initial spectrum of the native Sulfur Black 1, except that the absorbance for the former was about 63% of that for the latter, probably caused by an irreversible reductive transformation of .about.37% initial Sulfur Black 1.
When 0.4 .mu.M of recombinant Myceliophthora thermophila laccase, obtained as described in Example 1) was added at the beginning of the oxidation of leuco Sulfur Black 1, the initial rate and t.sub.1/2 increased and decreased respectively 2-fold. When the concentration of Myceliophthora thermophila laccase was increased to 0.8 .mu.M, the initial rate and t.sub.1/2 increased and decreased 4-fold, respectively (FIG. 6). The time profile of A.sub.627 became monophasic, in contrast to the biphasic profile of the uncatalyzed oxidation.
When Myceliophthora thermophila laccase was added after the first phase of the uncatalyzed oxidation of leuco Sulfur Black 1, an increase in reaction rate (of the second phase) was also observed (FIG. 6). With 0.4 and 0.8 .mu.M Myceliophthora thermophila laccase, the rate increased 3-fold and 6-fold, respectively.
The results demonstrated that, as for leuco vat dyes, oxidoreductases, such as Myceliophthora thermophila laccase, could catalyze the re-oxidation of the reduced Sulfur Black 1 by molecular oxygen.
The invention described and claimed herein is not to be limited in scope by the specific embodiments herein disclosed, since these embodiments are intended as illustrations of several aspects of the invention. Any equivalent embodiments are intended to be within the scope of this invention. Indeed, various modifications of the invention in addition to those shown and described herein will become apparent to those skilled in the art from the foregoing description. Such modifications are also intended to fall within the scope of the appended claims. In the case of conflict, the present disclosure including definitions will control.
Various references are cited herein, the disclosures of which are incorporated by reference in their entireties.

Number	Name	Date
3716325	Aspland	Feb 1973
3957424	Zeffren et al.	May 1976
4011042	Stitzel	Mar 1977
4036586	Rowe	Jul 1977
4131423	Kato	Dec 1978
4756037	McFadyen et al.	Jul 1988
5378246	Gurley	Jan 1995
5435809	Holst et al.	Jul 1995
5538517	Samain et al.	Jul 1996
5925148	Barfoed et al.	Jul 1999
5972042	Barfoed et al.	Mar 2000
6036729	Barfoed et al.	Mar 2000

Number	Date	Country
0504005	May 1995	EPX
2-104773	Apr 1990	JPX
6-316874	Nov 1994	JPX
8-127976	May 1996	JPX
9105839	May 1991	WOX
9533837	Dec 1995	WOX
9533836	Dec 1995	WOX

Enzymatic methods for dyeing with reduced vat and sulfur dyes

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