JP2003500043A - Use of microemulsion in fermentation process - Google Patents

Abstract

  (57) [Summary] The present invention relates to the use of an O / W emulsion in a fermentation process, comprising at least water, an emulsifier and an oil phase, which are (a) fatty acid alkyl esters, and / or (b) triglycerides of plant origin. Containing one or more selected compounds] and having an average droplet size in the range of 1 to 100 nm.

Description

Detailed Description of the Invention

[0001]     (Technical field)   The present invention relates to the use of microemulsions in fermentation processes.

BACKGROUND OF THE INVENTION Microbiological processes are increasingly used in the synthesis of complex natural substances and other organic compounds. Such processes include conversion / conversion under anaerobic or aerobic conditions involving microorganisms, particularly bacteria or fungi.
Various terms that are not always clearly distinguished from each other (eg biotransformation, biotransformation, fermentation) are used by experts in microbiological processes. "fermentation"
The term is used herein for the process by which microorganisms (preferably bacteria) are used for the conversion or synthesis of chemical compounds.

A key element in the development and optimization of fermentation processes is, in particular, the reaction medium in which the microbiological transformation takes place. This reaction medium, which is usually an aqueous solution or dispersion, has a particular influence on the yield and efficiency of the process. Microorganisms require bound forms of carbon, nitrogen and certain trace elements (e.g. calcium, iron, phosphorus or zinc) as nutrients to enable successful metabolism to the desired product. . Furthermore, the temperature and pH must be kept constant within a certain, usually narrow range. For more details, see the W. Crueger / A. Crueger manual "Biotechnolo.
gie-Lehrbuch der angewandten Mikrobiologie "[2nd edition 1984, R. Oldenbourg
Verlag]. Chapter 5 of this manual is particularly relevant to the basics of fermentation. That is, this reference is also specifically related to the disclosure of the present invention.
In addition to high-energy sugars and their derivatives, natural fats and oils and their derivatives (eg glycerol, glycerides, fatty acids or fatty acid esters) are additionally used as nutritional substances for microorganisms in many processes. It goes without saying that the culture medium must not contain components that can adversely affect the metabolism of the microorganism.

[0004] For example, German patent application DE 37 38 812 A1 describes a microbial process for producing α, ω-dicarboxylic acids, wherein the strain Candida trop
The icalis bacterium converts methyl laurate to the desired dicarboxylic acid. This conversion occurs in aqueous medium at pH 6.0 and a temperature of 30 ° C. In addition to microorganisms, the medium includes glucose as an energy source, ethoxylated sorbitan monooleate as an emulsifier, yeast extract, corn steep liquor and inorganic N and P.
Contains source. Methyl laurate is then added to the medium. In this document,
There is nothing that indicates the type of emulsion produced in the fermentor, ie the emulsion to which methyl laurate is added. European Patent Application Publication EP05359
39A1 describes a method for producing ω-9-polyunsaturated fatty acids, in which a suitable microorganism is used in an aqueous culture medium to reduce sugars as energy sources and inorganic or organic nitrogen sources. In the presence, as well as in the presence of fatty acid methyl esters, the desired polyunsaturated fatty acids are produced.

However, other known methods use only fatty compounds of the type described above as an energy source. This is especially from an economical point of view, since such fatty compounds are usually cheaper than sugars, starches and similar compounds. Park et al., "Journal of Fermentation and Bioengineering" [Volume 82, No.
2, 183-186, 1996] describe a fermentation process for producing tylosin, in which microorganisms of the strain Streptomyces fradiae were used in an aqueous medium, with rapeseed oil as the sole carbon source. It is present in a starting amount of about 60 g / L.

Also, the oxygen content in the medium or fermentation broth plays an important role in the fermentation process. In the aerobic process, oxygen acts as a substrate. The important factor is
Is the transfer of oxygen from the gas phase to the liquid phase containing the microorganisms sufficient for a particular process? An important parameter is the specific exchange surface, which is usually measured indirectly by the oxygen transfer coefficient k _La (see Crueger, Chapter 5, p. 71 et seq.). The adjustment of the optimum oxygen input is usually done by stirring the fermentation broth, which mixes oxygen or air with the liquid, so that gas exchange takes place at the interface. However, the considerable mechanical input of energy by vigorous agitation, as is done by Park et al., Can even destroy some of the culture, thus reducing the yield of the process. Furthermore, dead microorganisms may be further decomposed, and the resulting decomposition products may lead to poisoning of the culture, making economic production impossible. G.
From the study of Goma and JLRols [Biotech.Let., Vol.13, No.1, p.7-12, 1991],
The use of soybean oil in fermentation processes to produce antibiotics can lead to an improvement in the oxygen transfer coefficient k _La , which can lead to an increase in overall process yield for the same energy input (stirring). It is known.

DISCLOSURE OF THE INVENTION Here, the problem to be solved by the present invention is that, on the one hand, an inexpensive carbon source can be used and, on the other hand, it is subject to unacceptable severe mechanical stress due to stirring. It was to improve the fermentation process so that an adequate supply of oxygen to the microorganisms was guaranteed without exposing the microorganisms. We sought to find a way to minimize the mechanical input of energy in the fermentation process without any yield loss. It would be preferable for the yield to increase despite the reduction in energy input.

It has now been found that the use of special fine droplet oil-in-water (o / w) emulsions solves the above problems.

In a first aspect, the present invention is the use of an o / w emulsion in a fermentation process, the emulsion comprising at least water, an emulsifier and an oil phase, the oil phase comprising (a) a fatty acid alkyl An ester, and / or (b) a triglyceride of vegetable origin, containing one or more compounds from the group consisting of: Emulsion having a droplet size of 1-100 nm.

BEST MODE FOR CARRYING OUT THE INVENTION The emulsions of the present invention are distinguished in particular by the fineness of their droplets. This is a macroscopically uniform, at least two immiscible liquids as well as at least one nonionic or one ionic surfactant (preferably containing two hydrophobic residues). They are so-called microemulsions, which are defined as a mixture that is, and is optically clear, often of low viscosity and thermodynamically stable. The formation of microemulsions involves the condition where the oil / water interfacial tension is close to zero. In addition to at least one nonionic surfactant, usually other cosurfactants must be added to achieve this particular emulsion form. Reference "Introduction to Colloid and Surface Chemistry" [DJ Shaw,
Butterworth, 1992, p.269-270]. The droplet size of the emulsions used according to the invention is in the range 1-100 nm, preferably in the range 10-80 nm, and more specifically in the range 10-30 nm. The fineness of the oil droplets leads to a large surface between the oil phase and the water phase, thus providing a rapid contact between the microorganisms present in the water phase and the oil phase containing the nutrients. Also, the large surface facilitates gas (especially oxygen and CO ₂ ) exchange. In addition, the viscosity of the emulsion and thus of the whole fermentation medium is reduced. As a result, the stirring rate of the fermentation medium can be significantly reduced, which can increase the yield of the fermentation process.

According to the invention, the microemulsion is added to an aqueous fermentation medium containing microorganisms and optionally other auxiliaries and additives. The details of this process, and more specifically the rate and amount of emulsion addition, depend on the fermentation process and microbial strain selected and can be adapted by the expert to suit a particular situation.

In addition to water, microemulsions contain an oil phase, which contains compounds from the group consisting of (a) fatty acid alkyl esters, or (b) natural vegetable oils and their derivatives. Groups (a) and (b) are hydrophobic, water-insoluble or substantially water-insoluble compounds that act as nutrients (ie, energy sources) for the bacteria used in the fermentation process. Not only can it be a starting material (substrate) for the product obtained by bioconversion.

Suitable esters of group (a) are derived in particular from saturated, unsaturated, straight-chain or branched-chain fatty acids containing a total of 7 to 23 carbon atoms. In other words, these are the compounds of formula (I) below:

Embedded image R ¹ —COO—R ² (I) [wherein, R ¹ is a C _6-22 alkyl group, and R ² is a C _1-4 alkyl group]. Methyl and ethyl groups are preferred. Methyl esters are particularly preferred as component (a). Esters of formula (I) or methyl esters can be obtained in a known manner, for example by transesterification of triglycerides with methanol and subsequent distillation. Suitable fatty acids include caproic acid, heptanoic acid, caprylic acid, pelargonic acid, capric acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid,
Pentadecanoic acid, palmitic acid, heptadecanoic acid, stearic acid, nonadecanoic acid, arachidic acid and behenic acid. Representative examples of unsaturation include, for example, lauroleic acid, myristoleic acid, palmitoleic acid, petroselaidic acid, oleic acid,
Elaidic acid, ricinoleic acid, linoleic acid, linoleic acid, linolenic acid, gadoleic acid, arachidonic acid and erucic acid. Mixtures of the methyl esters of these acids are also suitable. It is particularly preferred to use a microemulsion containing a methyl ester from the group consisting of methyl oleate, methyl palmitate, methyl stearate and / or methyl pelargonate. But for example flaxseed oil,
Methyl based on natural fatty acid mixtures obtained from coconut oil, palm oil, palm kernel oil, olive oil, castor oil, rapeseed oil, sesame oil, soybean oil or sunflower oil (in the case of rapeseed oil and sunflower oil, new and old plants) Esters can also be used.

Suitable group (b) compounds are natural oils of vegetable origin. These are essentially triglyceride mixtures in which glycerol is always completely esterified by relatively long chain fatty acids. Particularly suitable vegetable oils are selected from the group consisting of peanut oil, coconut oil, linseed oil, palm oil, olive oil, palm kernel oil, castor oil, rapeseed oil, sesame oil, soybean oil and sunflower oil.

Peanut oil comprises, on average based on fatty acids, 54% by weight oleic acid, 24% by weight linoleic acid, 1% by weight linolenic acid, 1% by weight arachidic acid, 10% by weight palmitic acid and It contains 4% by weight of stearic acid and has a melting point of 2-3 ° C. Flaxseed oil is usually 5% by weight palmitic acid, 4% by weight stearic acid,
It contains 22% by weight of oleic acid, 17% by weight of linoleic acid and 52% by weight of linolenic acid, an iodine value of 155 to 205, a saponification value of 188 to 196 and about −.
It has a melting point of 20 ° C. Coconut oil is about 0.2-1 wt% hexanoic acid, 5-8 wt% octanoic acid, 6-9 wt% decanoic acid, 45-51 wt% lauric acid,
16-19% by weight myristic acid, 9-11% by weight palmitic acid, 2-3% by weight stearic acid, less than 0.5% by weight behenic acid, 8-10% by weight oleic acid and up to 1% by weight. Linoleic acid of is contained as a fatty acid component. This is 7.
It has an iodine number of 5 to 9.5, a saponification number of 0.88 to 0.90 and a melting point of 20 to 23 ° C. Olive oil is high in oleic acid [Lebensmittelchem.Ge
richtl.Chem., 39, 112-114, 1985]. Palm oil contains about 2% by weight myristic acid, 42% by weight palmitic acid, 5% by weight stearic acid, 41% by weight oleic acid, 10% by weight linoleic acid as the fatty acid component. Normally palm kernel oil has the following composition with respect to its fatty acid spectrum: 9% by weight caproic acid / caprylic acid / capric acid, 50% by weight lauric acid, 15% by weight myristic acid, 7% by weight palmitic acid. 2% by weight stearic acid, 15% by weight oleic acid and 1% by weight linoleic acid. Rapeseed oil is typically about 48% by weight erucic acid,
15% by weight oleic acid, 14% by weight linoleic acid, 8% by weight linolenic acid, 5
It contains, by weight, eicosenoic acid, 3% by weight palmitic acid, 2% by weight hexadecenoic acid and 1% by weight docosadienoic acid as fatty acid components. Rapeseed oil from new plants is relatively rich in unsaturated components. The usual fatty acid component here is 0
0.5% by weight erucic acid, 63% by weight oleic acid, 20% by weight linoleic acid, 9
% Linolenic acid, 1% eicosenoic acid, 4% palmitic acid, 2% hexadecenoic acid and 1% docosadienoic acid. 80 in castor oil
~ 85% by weight consists of glycerides of ricinoleic acid. Castor oil is about 7
It contains wt.% Oleic acid glyceride, 3 wt.% Linoleic acid glyceride and about 2 wt.% Palmitic and stearic acid glycerides. 55-65% by weight of the total fatty acids in soybean oil are polyunsaturated acids, more specifically linoleic acid and linolenic acid. Similarly for sunflower oil, its normal fatty acid spectrum is as follows, based on total fatty acids: about 1% by weight myristic acid, 3-10% by weight palmitic acid, 14-65% by weight. Oleic acid and 20
~ 75 wt% linoleic acid.

All the above numerical data on the fatty acid component of triglycerides depend on the quality of the raw material and can therefore vary. Especially preferred are microemulsions containing the nutrients of group (b) selected from coconut oil, sunflower oil and / or rapeseed oil.

An important constituent of the microemulsions used according to the invention is the emulsifier and the emulsifier system used. Preference is given to using nonionic emulsifiers, more particularly ethoxylated fatty alcohols and fatty acids, as emulsifiers.

The fatty alcohol ethoxylates in the teachings of the present invention have the formula (II) below:

Embedded image R ³ —O— (CH ₂ CH ₂ O) _n —H (II) [wherein, R ³ is a linear or branched saturated or unsaturated alkyl group containing 6 to 24 carbon atoms. And n is a number from 1 to 50]. Particularly preferred are compounds of formula (II) in which n is a number from 1 to 35, more specifically a number from 1 to 15. Other particularly preferred compounds of the formula (II) is a compound in which R ³ is an alkyl group containing 16 to 22 carbon atoms.

The compounds of formula (II) are obtained in a known manner by reaction of fatty alcohols with ethylene oxide under pressure, optionally in the presence of acid or base catalysts. Typical examples thereof are capron alcohol, capryl alcohol, 2-ethylhexyl alcohol, caprin alcohol, lauryl alcohol, isotridecyl alcohol, myristyl alcohol, cetyl alcohol, palmitoleyl alcohol, stearyl alcohol, isostearyl alcohol, oleyl alcohol,
Elaidyl alcohol, petroselinyl alcohol, linoleyl alcohol, linolenyl alcohol, eleostearyl alcohol, aralkyl alcohol, gadreyl alcohol, behenyl alcohol, erucyl alcohol and brassidyl alcohol, and for industrial use based on, for example, fats and oils Methyl ester or Roelen
Is an industrial mixture of the above alcohols obtained in the high-pressure hydrogenation of aldehydes derived from the oxo synthesis of ## STR3 ## and as a monomer fraction in the dimerization of unsaturated fatty alcohols. Industrial fatty alcohols containing 12 to 18 carbon atoms (eg,
Palm oil, palm oil, palm kernel oil or tallow fatty alcohol) are preferred.

The fatty acid ethoxylates which can also be used as emulsifier or as emulsifier component are preferably represented by the following formula (III):

Embedded image R ⁴ —CO ₂ (CH ₂ CH ₂ O) _m H (III) [wherein, R ⁴ is a linear or branched alkyl group containing 12 to 22 carbon atoms, and m is 5 to 50, preferably 15 to 35]. Typical examples are lauric acid, isotridecanoic acid, myristic acid, palmitic acid,
Palmitoleic acid, stearic acid, isostearic acid, oleic acid, elaidic acid, petroselinic acid, linoleic acid, linolenic acid, eleostearic acid, arachidic acid, gadoleic acid, behenic acid and erucic acid, and, for example, pressurization of natural fats and oils. Addition product of 20 to 30 mol of ethylene oxide to a technical mixture of the acid obtained in the hydrolysis or in the reduction of the aldehyde derived from Roelen's oxo synthesis. Preference is given to using the addition product of 20 to 30 mol of ethylene oxide to C _16-18 fatty acids.

Partial glycerides that can also be used as emulsifiers are preferably represented by the following formula (IV):

[Chemical 5] [In the formula, COR ⁵ is a linear or branched acyl group containing 12 to 22 carbon atoms, and x, y and z are both 0 or 1 to 50, preferably 15 to 3
It is a number of 5]. Typical examples of partial glycerides suitable for the purpose of the present invention include lauric acid monoglyceride,
Coconut oil fatty acid monoglyceride, palmitic acid monoglyceride, stearic acid monoglyceride, isostearic acid monoglyceride, oleic acid monoglyceride and tallow fatty acid monoglyceride, and these and 5 to 50 mol, preferably 2
It is an addition product with 0 to 30 mol of ethylene oxide. COR ⁵ is 16-18
Preference is given to using monoglycerides or industrial mono / diglyceride mixtures which are rich in monoglycerides (IV), which are straight-chain acyl groups containing 1 carbon atom.

Other suitable emulsifiers are, for example, nonionic surfactants from at least one of the following groups: (i) 2 to linear fatty alcohols containing 8 to 22 carbon atoms, Addition products of -30 mol ethylene oxide and / or 0-5 mol propylene oxide; (ii) glycerol monoesters and diesters and sorbitan monoesters and diesters of saturated and unsaturated fatty acids containing 6 to 22 carbon atoms; These ethylene oxide adducts; (iii) alkyl mono- and oligoglycosides containing 8 to 22 carbon atoms in the alkyl group and their ethoxylated analogues; (iv) to castor oil and / or hydrogenated castor oil, 15 -60 mol ethylene oxide addition product; (v) polyol ester, especially polyglycerol Stells, such as polyglycerol polyricinoleate or polyglycerol poly-12-hydroxystearate (mixtures of compounds from several of these groups are also suitable); (vi) to castor oil and / or hydrogenated castor oil, (Vii) linear, branched, unsaturated or saturated C _6/22 fatty acids, ricinoleic acid and 12-hydroxystearic acid, and glycerol, polyglycerol,
Partial esters based on pentaerythritol, dipentaerythritol, sugar alcohols (eg sorbitol) and polyglucosides (eg cellulose); (viii) wool wax alcohols; (ix) polyalkylene glycols.

Addition products of ethylene oxide and / or propylene oxide of fatty acids to glycerol mono- and diesters and sorbitan mono- and diesters or to castor oil are known commercial products. These are homolog mixtures whose average degree of alkoxylation corresponds to the ratio between the substrate undergoing the addition reaction and the amount of ethylene oxide and / or propylene oxide.

It is particularly preferred to use an emulsifier of group (iii), ie an alkyl glycoside. Alkyl and alkenyl oligoglycosides are known nonionic surfactants of formula (V) below:

Embedded image R ⁶ O— [G] _p (V) [wherein R ⁶ is an alkyl and / or alkenyl group containing 4 to 22 carbon atoms, and G is 5 or 6 carbon atoms. Is a sugar unit containing p is a number from 1 to 10]. These can be obtained by related methods of manufacturing organic chemistry. Biermann et al. Review paper [Starch / Staerke 45, 281 (1993)], B. Salka [Cosm.Toil. 108, 89 (1993)]
And J. Kaehre et al. [SOEFW-Journal, No. 8, 598 (1995)] are cited as representative examples of detailed literature available for this subject.

These alkyl and / or alkenyl oligoglycosides can be derived from aldoses or ketose (preferably glucose) containing 5 or 6 carbon atoms. That is, the preferred alkyl and / or alkenyl oligoglycosides are alkyl and / or alkenyl oligoglucosides. General formula (V)
The index p in indicates the degree of oligomerization (DP), ie the distribution of mono and oligoglycosides, and is a number from 1 to 10. The value p of a given alkyl oligoglycoside is the quantity measured and calculated by analysis, which is a fraction, although the p of a given compound must always be an integer and will in particular take values from 1 to 6. Is normal. Preference is given to using alkyl and / or alkenyl oligoglycosides having an average degree of oligomerization p of 1.1 to 3.0. Less than 1.7, especially 1.2-1.
Alkyl and / or alkenyl oligoglycosides with a degree of oligomerization between 4 are preferred from the application point of view. The alkyl or alkenyl group R ⁶ is 4 to
It can be derived from a primary alcohol containing 11 and preferably 8 to 10 carbon atoms. Representative examples thereof are butanol, capron alcohol, capryl alcohol, caprin alcohol and undecyl alcohol, and the alcohols obtained, for example, in the hydrogenation of industrial fatty acid methyl esters or in the hydrogenation of aldehydes derived from Roelen's oxo synthesis. Is an industrial mixture of. C ₈
Alkyl oligoglucosides having a chain length of ~ C ₁₀ (DP = 1 to 3) [These are obtained as the first fraction in the separation of industrial C _8-18 coconut oil fatty alcohols by distillation and 6% by weight as impurities. Less than C ₁₂ alcohol], as well as alkyl oligoglucosides based on industrial C _9/11 oxo alcohols (DP
= 1-3) is preferable. Further, the alkyl or alkenyl group R ⁶ has 12 to 22
It can also be derived from primary alcohols containing 1, preferably 12 to 14 carbon atoms. Typical examples thereof are lauryl alcohol, myristyl alcohol, cetyl alcohol, palmitoleyl alcohol, stearyl alcohol, isostearyl alcohol, oleyl alcohol, elaidyl alcohol, petroselinyl alcohol, aralkyl alcohol, gadreyl alcohol, behenyl alcohol, erucyl alcohol. , Brassil alcohol, and industrial mixtures of these alcohols obtained as described above. Alkyl _{oligoglucosides} based on hydrogenated C _12/14 coconut oil alcohols with DP of 1 to 3 are preferred. When the alkyl glycosides of formula (V) are used as emulsifiers, it may be advantageous to use with them small amounts of polyhydroxycarboxylic acids (preferably citric acid) as compounding aids. In such a case, the polyhydroxy acid is used in an amount of 0.1-3.0% by weight, preferably 0.1-1.0% by weight.

The microemulsion used according to the invention is preferably 20-90% by weight.
, More preferably 30-80% by weight, most preferably 30-60% by weight of water. The balance up to 100% by weight is constituted by the oil phase and the emulsifier and optionally other auxiliaries and additives. The oil phase itself is preferably 10-8.
0% by weight, more preferably 20-70% by weight, most preferably 25-55% by weight
Present in an amount of. In a preferred embodiment, the oily phase contains only component (a) or (b) or a mixture of these components. The use of emulsions containing an oil phase and an aqueous phase in a 1: 1 weight ratio is particularly preferred. The emulsifier or emulsifier system is preferably 10
-50% by weight, more preferably 15-45% by weight, most preferably 20-40% by weight.

According to the invention, the described microemulsions can be used in all types of fermentation processes. Any type of process known to the expert can be used, such as batch or fed-batch fermentation and continuous fermentation. Moreover, any fermentation system known to the expert can be used. For more information on this, see Crueger (pages 50-70). Moreover, the use of microemulsions is not limited to a particular microorganism. On the contrary, the emulsion can be used for fermentatively producing or converting any compound known to the expert.
The conventional fermentation process (Crueger No. 197-242) used primarily in the synthesis of antibiotics.
(See page), the emulsion described, in microbial conversion (bioconversion),
It is also suitable for use in the conversion of, for example, steroids and sterols, antibiotics and pesticides or the production of vitamins (see Crueger pp. 254-273). However, the emulsions described are preferably used in fermentation processes for producing antibiotics (eg cephalosporins, tylosin or erythromycin).

Generally, the microemulsion is suitably added to an aqueous fermentation broth containing a microbial and nitrogen source and trace elements and optionally other auxiliaries, especially defoamers. Suitable nitrogen sources are, for example, peptone, yeast or malt extract, corn steep liquor, urea or lecithin. Trace elements are in the form of inorganic salts, for example:
It may be present in the form of sodium or potassium nitrate, ammonium nitrate, ammonium sulfate, iron sulfate and the like. It may be advantageous to add other additives (eg defoamers or nitrogen sources) to the microemulsion itself.

Examples Various microemulsions were prepared by mixing the starting materials. These compositions are shown in Table 1 below. Droplet size was measured using a Malvern Mastersizer 2000. These emulsions are suitable, for example, as the sole source of nutrients for the fermentation process and can be added directly to the aqueous fermentation broth.

[0030]

[Table 1]

─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Jean-Pierre Molitor             Federal Republic of Germany Day-40589 Düssel             Dolph, Am Neckessfeld 28 (72) Inventor Christian Duo             France, F-77310 Boissis le Lo             Wa, Boulevard de Seine No. 53 (72) Inventor Benoit Abriva             United States 45140 Cincinnati, Ohio             Tee, Loveland, Stonebridge Do             Live 9871 (72) Inventor Bent Logge             Federal Republic of Germany Day-40227 Düssel             Dolph, Linnie Strasse 46 F-term (reference) 4B065 AA01X AA57 BB09 BB10

Claims (10)

[Claims] 1. An oil phase containing at least water, an emulsifier, and (a) a fatty acid alkyl ester, and / or (b) a triglyceride of plant origin, containing one or more compounds selected from the group: In a fermentation process, characterized in that the emulsion has a droplet size of 1-100 nm. 2. Use according to claim 1, characterized in that fatty acid methyl ester is used as component (a). 3. Use according to claim 1 or 2, characterized in that an emulsion with an average droplet size of 10 to 80 nm, preferably 10 to 50 nm, is used. 4. An emulsion containing water in an amount of 20 to 90% by weight, preferably 30 to 80% by weight, more specifically 30 to 60% by weight, is used. Use according to any one of. 5. An emulsion containing an oil phase in an amount of 10 to 80% by weight, preferably 20 to 70% by weight, more specifically 25 to 55% by weight, is used. Use according to any of 4. 6. In an oil phase, the following formula (I): embedded image R ¹ —COO—R ² (I) [wherein R ¹ is a C _6-22 alkyl group and R ² is It is a methyl group] The emulsion containing fatty acid methyl ester shown by these is used, The use in any one of Claims 1-5 characterized by the above-mentioned. 7. The emulsion according to claim 1, wherein an emulsion containing methyl oleate, methyl palmitate, methyl stearate and / or methyl pelargonate in the oil phase is used. use. 8. Use according to any of claims 1 to 7, characterized in that an emulsion containing coconut oil, sunflower oil and / or rapeseed oil in the oil phase is used. 9. Use according to any of claims 1 to 8, characterized in that an emulsion containing an alkyl oligoglycoside is used as emulsifier. 10. Emulsion containing an emulsifier in an amount of 10 to 50% by weight, preferably 15 to 40% by weight, more specifically 20 to 35% by weight, is used. Use according to any one of.