Bleach composition

Abstract: The bleaching activity of an enzymatic bleach composition comprising a C₁-C₄ alkanol oxidase and a C₁-C₄ alkanol is improved by addition of a C₁-C₄ aldehyde oxidase having a lower K m than the C₁-C₄ alkanol oxidase.

Description: The present invention relates to a bleach composition and to its use in detergent compositions. More particularly, it relates to a bleach composition comprising a hydrogen peroxide precursor which comprises a C₁-C₄ alkanol oxidase and a C₁-C₄ alkanol. Such bleach compositions are described in British patent application 2,101,167. They are advantageously used in detergent compositions for fabric washing in which they may effectively provide a low-temperature enzymatic bleach system. In the wash liquor, the alkanol oxidase enzyme catalyses the reaction between dissolved oxygen and the alkanol to form an aldehyde and hydrogen peroxide. In order to obtain a significant bleach effect at low wash temperatures, e.g. 15-55°C, the hydrogen peroxide must be activated, using a bleach activator. The preferred bleach activator used to that end is tetraacetyl ethylene diamine (TAED), which yields peracetic acid upon reacting with the hydrogen peroxide, the peracetic acid being the actual bleaching species. It is essential in using such bleach compositions that they are essentially free of catalase activity, because catalase efficiently catalyses the decomposition of the hydrogen peroxide formed by the alkanol oxidase enzyme. Therefore, the alkanol oxidase enzyme must be thoroughly purified in order to liberate it from any contaminating catalase activity. As catalase is abundantly present in all naturally occurring micro-organisms serving as a source for alkanol oxidase, this purification process is essential and it must be carried out extensively, which adds to the cost of the bleaching compositions. The problem of catalase contamination may be overcome by using a catalase-free micro-organism as the source of alkanol oxidase. This approach has been described in European patent applications 242,007 and 244,920. European patent application 242,007 discloses the preparation of catalase-free methanol oxidase by aerobic fermentation of a methylotrophic catalase-negative yeast, which is allowed to grow in a nutritive medium in the presence of an inducing substrate and another source of carbon. The molar ratio of inducing substrate to other carbon source is such that the yeast and the methanol oxidase do not suffer from any harmful effects from the oxidation of the inducing substrate. European patent application 173,378 relates to the production of oxidoreductases by means of recombinant-DNA techniques. It discloses bleaching compositions containing, inter alia, aldehyde oxidase and a suitable substrate for the aldehyde oxidase. However, even when using catalase-free preparations of the alkanol oxidase enzyme, the bleaching performance of such enzymatic bleach compositions, especially in domestic washing machines of the European type, has not been as good as expected. It is therefore an object of the present invention to provide an enzymatic bleach composition of the aforementioned kind, having improved bleaching properties. It has now been found that the drawbacks of the known enzymatic bleach compositions containing a C₁-C₄ alkanol oxidase and a C₁-C₄ alkanol may be overcome by the bleach composition of the present invention, which is characterised in that it further comprises a C₁-C₄ aldehyde oxidase having essentially no substrate specificity for nitrogen-containing aromatic heterocyclic compounds, the K m of the aldehyde oxidase for the aldehyde resulting from oxidation of the alkanol being lower than that of the alkanol oxidase for said alkanol. Aldehyde oxidases (EC 1.2.3.1) are known in the art. They catalyse the reaction between an aldehyde, oxygen and water to form a carboxylic acid and hydrogen peroxide. Aldehyde oxidases of animal origin not only act upon aldehydes, but also upon various nitrogen-containing aromatic heterocyclic compounds. For the purpose of the present invention, aldehyde oxidases having a greater substrate specificity are used. Such aldehyde oxidases can be obtained from bacteria, for example, described in the European patent application 091,810. It will be evident that the aldehyde oxidase must also be essentially free of catalase activity, since this enzyme would efficiently decompose any hydrogen peroxide formed. To obtain a catalase-free aldehyde oxidase preparation, the enzyme can be purified according to known methods, for instance as described in the British patent application 2,101,167. Alternatively, the enzyme could be produced from a genetically modified or engineered catalase-free micro-organism. Although the applicants do not wish to restrict the present invention by a specific explanation of the observed results, it is believed that the aldehyde oxidase enzyme improves the performance of a detergent composition comprising an alkanol, an alkanol oxidase and a bleach activator by preventing the build-up of inhibiting concentrations of aldehyde. Supportive for this idea is the finding that certain chemical compounds which are known to react with aldehydes, such as semicarbazide, are also capable of improving the performance of the known alkanol oxidase based bleaching compositions. However, the addition of catalytic amounts of aldehyde oxidase according to the present invention is much to be preferred to the addition of substantial amounts of a highly reactive chemical compound like semicarbazide. The bleach compositions according to the present invention are advantageously used in detergent compositions, which may be in any suitable physical form. In view of the presence of the alkanol, the detergent composition is most often an aqueous or non-aqueous liquid, paste or gel. To that end, the bleach composition can contain the usual compounds of a detergent composition, such as surfactants, builders, other enzymes, such as proteolytic, amylolytic, cellulolytic and lipolytic enzymes and perfumes. Suitable surfactants or detergent-active compounds are soap or non-soap anionics, nonionics, cationics, amphoteric or zwitterionic compounds. Examples thereof are given in the British patent application 2,101,167. The quantity of alkanol oxidase to be employed in compositions according to the invention should be at least sufficient to provide, after dilution or dissolution of the composition with water and interaction with the alkanol, sufficient hydrogen peroxide to bleach standard tea-stained fabric. The amount of alkanol oxidase will depend on its specific activity and the activity of any residual catalase that may be present, but by way of example it can be stated generally that the detergent composition according to the invention will contain from 10 to 1000, preferably from 20 to 500 units alkanol oxidase per g or ml of the detergent composition, a unit of enzyme activity being defined as the quantity required to convert 1 µmole of substrate per minute under standard conditions. When the composition is then diluted 100 times by addition to water to provide a medium suitable for washing and bleaching fabrics, the medium will contain from 0.1 to 10, preferably from 0.2 to 5 units of enzyme per ml which, on interaction with the alkanol substrate also present, will produce sufficient hydrogen peroxide to bleach standard tea-stained fabric. The amount of aldehyde oxidase will equally depend on its specific activity and purity. The detergent composition according to the present invention contains preferably from 10 to 1000, more preferably from 20 to 500 units aldehyde oxidase per g or ml of the composition. Upon dissolution or dilution 100 times by addition of water, the wash medium will then contain from 0.1-10, preferably 0.2-5 units/ml. As a substrate for the alkanol oxidase, the bleach composition of the present invention comprises a C₁-C₄ alkanol, preferably a primary alkanol. The especially preferred alkanol is ethanol. The quantity of the alkanol to be employed should be at least sufficient to provide, after dilution of the composition with water and interaction with the alkanol oxidase, sufficient hydrogen peroxide to bleach standard tea-stained fabric. A suitable quantity of alkanol forms from 2 to 25%, preferably 5 to 20% and most preferably 5 to 12% by weight of the composition. The quantity of hydrogen peroxide precursor containing alkanol oxidase, aldehyde oxidase and the alkanol in the composition, which is sufficient on dilution of the composition with water to bleach standard tea-stained fabric, should be such that, when the composition is diluted with 100 times its weight of water, the enzyme and substract will reaction, at a temperature of 40°C and a pH of 9, to yield hydrogen peroxide at a concentration of at least 2 mM. Preferably, the alkanol oxidase, aldehyde oxidase and the alkanol are present in sufficient quantity to yield under these conditions hydrogen peroxide at a concentration of at least 5 mM, most preferably 20 mM or even higher. Compositions according to the invention will also preferably contain a bleach activator to enable hydrogen peroxide generated at a low temperature of for example 15°-55°C to bleach soiled fabric. Bleach activators are conventionally organic compounds having one or more acyl reactive acyl residues, which at relatively low temperatures react with hydrogen peroxide causing the formation of organic peracids, the latter providing for a more effective bleaching action at lower temperatures than hydrogen peroxide itself. The best known organic activator of practical importance is N,N,N′,N′-tetraacetyl ethylenediamine (TAED). Examples of other organic bleach activators are other N-acyl substituted amines, for example tetraacetyl methylene diamine, carboxylic acid anhydrides, for example succinic, benzoic and phthalic anhydrides; carboxylic acid esters, for example sodium acetoxy benzene sulphonate, sodium p-sulphonated phenyl benzoate; acetates, such as glucose pentaacetate and xylose tetraacetate, and acetyl salicylic acid. Organic bleach activators can be employed in compositions according to the invention at a concentration of from 0.1 to 10%, preferably from 0.5 to 5% by weight. It is also possible to use as bleach activators heavy metal ions of the transition series, such as cobalt, which catalyse peroxide decomposition, optionally together with a special type of chelating agent for said heavy metal such as are described in U.S. patent 3,156,654. Instead of or in addition to the above-mentioned bleach activators, the compositions according to the present invention might comprise an enzymatic bleach activator system in the form of an esterase and/or lipase enzyme, capable of generating peracids from glycerides and hydrogen peroxide, such as described in the European patent application 253,487, for example. The invention will be further illustrated by means of the following non-limiting Examples. Examples 1-4 The bleaching activity of liquid detergent compositions according to the present invention was tested using a liquid detergent having the following formulation: wt.% Linear Alkyl Sulphonate 7.4 Groundnut Fatty Acid 0.8 C₁₃-C₁₅ 7EO Nonionic 2.2 Caustic Soda 1.2 KOH 0.4 Glycerol 5.6 Sodium Tetraborate.10 aq 3.1 Sodium Tripolyphosphate 23.0 Sodium Carboxymethylcellulose 0.1 Enzyme - Alcalase 2.34 L 0.5 Minors 0.6 Water to 100.0 A wash liquid was prepared by dissolving 10 g of the above formulation in 1 litre water of 14°FH and supplementing the solution with the following additives to the given concentrations: ethanol (20 mM), TAED (0.8 mM) and borax 10 (10 mM). The enzyme or enzyme combinations given in Table I were added to a series of closed 250 ml polyethylene flasks containing 25 ml wash liquor and a piece of 5 x 5 cm of BC-1 test cloth. The flasks were incubated for 45 minutes at 40°C in a shaking bath at a frequency of 5 Hz. After the wash, the BC-1 test cloth reflection was measured at 450 nm and compared with a control cloth washed in the absence of bleaching enzymes. The methanol oxidase used was completely free from catalase activity, as described in European patent application 0,244,920. It was obtained by harvesting yeast cells cultured as described in EP-A-0,244,920, centrifuging the cells and freeze-drying the material of the centrifuge pellet. The result of this procedure is rather generally suitable for adding to the compositions of the invention, and the dry composition can have an activity level of e.g. 0.7U/mg or more. Aldehyde oxidase as described in European patent application 0,091,810 was obtained from Kyowa Hakko Kogyo Co. Ltd. It was produced from a Pseudomonas sp. No. 6233 FERM P-6467. The enzyme was separated from accompanying catalase activity by selective precipitation with polyethyleneimine (J. Jendrisak, J. Cell. Bioch., Suppl. 11c, 116 (1987)), followed by affinity chromatography (IMAC method, E. Sulkowski, Trends in Biotechnology 3 , 1-7 (1985)). The ratio of catalase units/aldehyde oxidase units of the final preparation was lower than 0.1. The results of the bleaching tests are shown in Table I. Example Methanol Oxidase Aldehyde Oxidase AR (U/ml) (U/ml) 1 0.6 - 5.2 2 1.2 - 4.8 3 0.6 0.3 6.0 4 0.6 0.6 7.2 It is apparent from Table I that increasing the amount of methanol oxidas does not result in an improved bleaching performance. The further addition of aldehyde oxidase, however, results in a significantly improved action. The methanol oxidase used here had a Km for methanol of about 7.2 mM, while the Km of the aldehyde oxidase for acetaldehyde was about 0.12 mM. Examples 5-8 The examples 1-4 were repeated, using the following liquid detergent stock solution: wt.% Linear Alkyl Sulphonate 7.2 Linear Ether Sulphate 2.4 C₁₄-C₁₅ 3EO Nonionic 2.4 Zeolite 20.0 Polymer - Sokalan CP5 3.0 Citric Acid 1.5 Enzyme - Savinase 8.0 L 0.6 Glycerol 8.0 Sodium Tetraborate.10 aq 5.7 Calcium Chloride 0.15 Minors 0.8 Water to 100.0 The results of the bleaching tests are given in Table II. Example Methanol Oxidase Aldehyde Oxidase AR (U/ml) (U/ml) 5 0.6 - 5.2 6 1.2 - 4.8 7 0.6 0.3 5.8 8 0.6 0.6 6.6 Table II confirms the results which are shown in Table I for a phosphate-containing detergent composition. The addition of aldehyde oxidase effects a clear increase in bleaching performance of the zeolite-containing liquid detergent composition.

Claims: Bleach composition comprising a hydrogen peroxide precursor, which comprises a C₁-C₄ alkanol oxidase and a C₁-C₄ alkanol, said composition being essentially free of catalase, characterized in that it further comprises a C₁-C₄ aldehyde oxidase having essentially no substrate specificity for nitrogen-containing aromatic heterocyclic compounds, the K m of the aldehyde oxidase for the aldehyde resulting from oxidation of the alkanol being lower than that of the alkanol oxidase for said alkanol. Bleach composition according to claim 1, further comprising a bleach activator. Bleach composition according to claim 2, wherein the bleach activator is tetraacetyl ethylene diamine. Bleach composition according to any of the preceding claims, comprising methanol oxidase, ethanol and aldehyde oxidase. Detergent composition comprising a bleach composition according to any of the preceding claims.

Inventors: APPEL ADRIANUS CORNELIS MARIA, HAVERKAMP JOHAN, HORA JIRI, APPEL, ADRIANUS CORNELIS MARIA, HAVERKAMP, JOHAN, HORA, JIRI
Applicants: UNILEVER NV, UNILEVER PLC, UNILEVER N.V.
Application year: 1989
Main classification: C11D3
IPC codes: C11D7, D06L3, C12S11, C11D3