Patent Application
20080242879
This application claims priority under 35 U.S.C. Section 119 of European Patent Application No. 07006847.3 filed Apr. 2, 2007, the contents of which are incorporated herein in its entirety.
This invention relates to a process for enriching polyunsaturated fatty acid (hereinafter “PUFA”) acyl groups in a fatty acid ester mixture which contains PUFA acyl groups and other fatty acid acyl groups, comprising the steps of preparing a fatty acid ester mixture containing PUFA acyl groups and other fatty acid acyl groups, contacting this mixture with a lipase and with water, the water having a pH above 7 and containing a metal salt which forms poorly soluble salts with free fatty acids in water at a pH above 7 and the lipase having a negative selectivity for PUFA acyl groups, so that the other fatty acid acyl groups are hydrolytically split off from the fatty acid ester mixture more rapidly than the PUFA acyl groups, and separating the second fatty acid ester mixture enriched with PUFA acyl groups.
In the context of the present invention, a fatty acid is a saturated or unsaturated, branched or unbranched aliphatic carboxylic acid. Fatty acids can be saturated, mono-unsaturated, di-unsaturated or at least tri-unsaturated.
In the context of the present invention, fatty acids as such are also referred to as free fatty acids. By comparison, the expression “fatty acid acyl group” in the context of the present invention means the single-bonded residue which is obtained by removal of the H atom from the COOH group. Accordingly, fatty acid acyl groups occur, for example, in free fatty acids. They also occur in esters of fatty acids, for example, esters with glycerol, the so-called glycerides.
A fatty acid glyceride is an ester of glycerol and one, two, or three fatty acids. If only one OH group of the glycerol is esterified with a fatty acid, the ester is known as a monoglyceride. If two OH groups of the glycerol are each esterified with a fatty acid, the ester is known as a diglyceride. If all three OH groups of the glycerol are each esterified with a fatty acid, the ester is known as a triglyceride.
In the context of the present invention, the initials “PUFA” stand for “polyunsaturated fatty acid”, i.e. a fatty acid which is at least tri-unsaturated.
An omega-3-fatty acid is an at least tri-unsaturated fatty acid and is thus a PUFA. An omega-3-fatty acid has a double bond between the third and fourth carbon atoms counting from the methyl end, the methyl C atom being counted as the first C atom. Special omega-3-fatty acids are EPA ((all-Z)-5,8,11,14,17-eicosapentaenoic acid) and DHA ((all-Z)-4,7,10,13,16,19-docosahexaenoic acid).
In the prior art, PUFA glycerides, i.e. glycerides in which PUFA acyl groups make up a large proportion of all the fatty acyl groups present, are produced in particular by one of the following two processes:
Process (1), the enzymatic triglyceride synthesis, is described, for example, in EP-A 0 528 844.
Process (2) or the selectivity of lipases for PUFAs in the hydrolysis of glycerides is disclosed in several patent applications, cf. for example WO 97/19601, WO 95/24459, WO 96/37586, WO 96/37587, EP-A 0 741 183, WO 96/26287, WO 00/73254, WO 04/043894, WO 00/49117 and WO 91/16443.
The following is known from the prior art on enzyme selectivities for PUFAs. Most lipases and phospholipases have a negative selectivity for PUFAs by comparison with other fatty acids typically present in vegetable and fish oils. By “negative selectivity” is meant that the lipases hydrolytically split off the other fatty acid groups from glycerides more rapidly than the PUFA acyl groups. Accordingly, the enzymatic enrichment of PUFAs generally proceeds via a modification of the other “non-PUFA” fatty acids. This can be done by esterification, transesterification, or hydrolysis of esters.
Negative selectivities for PUFAs are described, for example, for Candida and Mucor lipases. Some enzymes, for example, those isolated from cold water fish, have a positive selectivity for PUFAs.
The microfungus Thermomyces lanugenosus was formerly known as Humicola lanuginosa. For this reason, there are a large number of scientific treatises on lipase from Thermomyces under the name of Humicola. The lipase from Thermomyces is distinguished in particular by an activity optimum in the alkaline pH range and by high stability, even at a pH of 12 to 13. The enzyme is used in detergents. The articles Biotechnology and Bioengineering 48 (1), 1995; pages 7848 and Biotechnology and Bioengineering 48 (3), 1995; pages 190-196 provide a good overview of the properties of Thermomyces lipase.
Lipase from Thermomyces lanugenosus is commercially obtainable, for example, as a liquid preparation with the name Lipozym® TL 100 L or Lipolase® 100 L, from Novozymes A/S, Bagsvaerd, Denmark.
The other lipases used in the following Examples are also commercially obtainable. The lipase from Geotrichum candidum was self-produced.
In the following, U stands for “unit” and is an indication of the activity of enzymes. 1 U is the reaction of 1 μmol substance per minute under certain, defined reaction conditions.
Determining the activity of lipase from Thermomyces lanugenosus is carried out as follows (for Novozymes A/S by the method for Lipozym® and Lipolase®): the release of butyric acid from glycerol tributyrate is determined at 30° C./pH 7. A 0.16 M tributyrin solution is used for this purpose and butyric acid is titrated with NaOH at a constant pH. 1 unit corresponds to the activity which releases 1 μmol butyric acid from tributyrin per minute.
Fish oils consist essentially of triglycerides containing a mixture of saturated, mono- and poly-unsaturated fatty acids, more particularly with a high proportion of 5×- and 6×-unsaturated fatty acids, which may be used as a health-promoting food supplement. Since the highly unsaturated fatty acids in particular are health-promoting, there is an advantage in enriching them. This can be done, for example, by selective removal of the non-highly unsaturated fatty acids from the triglycerides, for example through selective enzymatic hydrolysis with lipases.
Owing to their large number of double bonds, PUFAs are highly temperature and oxidation-sensitive. Isomers can easily be formed through migration of the double bonds while peroxides and polymers can easily be formed through oxidation. Where polyunsaturated fatty acids are used in food supplements and pharmaceutical products, it is important to avoid such secondary products in the production process. Particularly in the production of highly enriched PUFAs from fish oils, which are particularly interesting, for example, for administration in the form of capsules, a loss of quality of the end product rapidly occurs through thermal enrichment processes.
A typical working-up process known from the prior art is the distillation-based fractionation of, generally, PUFA ethyl esters which are obtained from the fish oils by chemical transesterification. In this process, the PUFA esters are exposed to severe heat stress by—partly—repeated fractionation.
An alternative process is urea fractionation. Although this process does not involve significant heat stress, it is attended by a serious danger in the formation of toxic secondary products which contaminate the PUFAs.
An alternative method to the enrichment of PUFAs is low-temperature enzymatic fractionation. For example, PUFAs can be enriched in the form of their glycerides or their ethyl esters. The enrichment can be carried out by selective hydrolysis, selective synthesis, or selective transesterification.
However, after the selective enzymatic reaction, there remains the problem of separating the various fractions (for example fatty acid and glycerides) which, generally, are completely soluble in one another. The reaction mixtures from the enzymatic enrichment are generally separated by distillation in a second step. This separation also exposes the PUFAs to heat stress with the risk of a loss of quality.
European patent application 06023997 discloses a single-stage process for the production of zinc ricinoleate in which castor oil is hydrolyzed in the presence of suitable enzymes, preferably lipases, and at the same time reacted with zinc oxide in aqueous solution to form zinc ricinoleate.
WO 2005/007864 discloses a process for the production of carboxylic acid salts and, more particularly, a process for the enzymatic hydrolysis of fish oils in alkaline medium in the presence of calcium salts, the calcium salts of the PUFAs present in the fish oils being obtained.
WO 2005/00784 discloses that the most suitable enzyme for the alkaline hydrolysis of esters is lipase from Thermomyces lanugenosus. This lipase was specially developed for detergent applications and shows high activity at alkaline pH values. The lipase is capable of producing soaps (i.e. metal salts) from esters in a one-step reaction in the presence of, for example, Ca(OH)2 or Mg(OH)2. The soaps can then be isolated from the reaction solution by filtration.
WO 07/119811 discloses a method for production of a condensed PUFA oil, which comprises performing an alcoholysis reaction of a PUFA-containing oil-and-fat with a lipase in the presence of at least one compound selected from magnesium oxide, magnesium hydroxide, calcium oxide and calcium hydroxide and a small quantity of water and separating a glyceride fraction.
In principle, most enzymes are capable of catalyzing an ester hydrolysis under alkaline conditions, at least for a short time. Thermomyces lipase has the best price/performance ratio of all commercially obtainable lipases.
By way of the present invention, it has now also been discovered that Thermomyces lipase has a negative selectivity for PUFAs.
The use of alkaline hydrolysis for enriching PUFAs is also not described in the prior art.
The problem to be addressed by the present invention was to provide a process which would enable the PUFA acyl groups present in a mixture of fatty acid glycerides containing PUFA acyl groups to be enriched without exposure to heat stress.
The problem stated above is solved by the following process according to the invention. The present invention relates to a process for enriching PUFA acyl groups in a first fatty acid ester mixture which contains PUFA acyl groups and other fatty acid acyl groups, comprising:
The following processes are particular embodiments of the process according to the invention:
The present invention also relates to the use of a lipase for enriching PUFA acyl groups in a first fatty acid ester mixture containing PUFA acyl groups and other fatty acid acyl groups, the enrichment being carried out by the process according to the invention or by a process which is a particular embodiment of the present invention.
More particularly, a process is provided in which:
More particularly, a process has been developed in which the selective hydrolysis is directly carried out in the presence of an extractant, so that the enriched PUFA ester fraction can be directly isolated after the reaction.
Suitable lipases are any lipases which have a negative selectivity for PUFAs. Lipases with a high activity under alkaline reaction conditions are preferred. Thermomyces lanugenosus lipase is particularly preferred. The lipase is preferably used in free form.
Suitable PUFA-containing fatty acid ester mixtures are, in particular, fish oils, enriched glycerides, PUFA-containing ethyl esters, and already concentrated PUFA ethyl esters.
The water to oil ratio (w/w) may be freely selected and, more particularly, is in the range from 10:1 to 1:10 (oil=fatty acid ester mixture).
Preferred metal salts are divalent hydroxides, oxides or carbonates. Ca(OH)2 or Mg(OH)2 are particularly preferred.
The quantity of metal salts used, based on the non-PUFA part of the ester, is preferably 0.3 to 1.5 mol divalent salt per mol non-PUFA fatty acid bound in the ester (corresponds stoichiometrically to 0.6 to 3 times the quantity).
The process of the invention is carried out at temperatures which range from 20 to 60° C., and preferably 25 to 45° C.
The process according to the invention is preferably carried out as a batch reaction, preferably in an inert atmosphere at normal pressure.
The extractant may either be directly introduced into the reaction or used for extraction after the hydrolysis step.
Preferred extractants are water-immiscible solvents such as, for example, alkanes, ethers, etc. Iso-octane, octane, heptane and hexane are particularly preferred.
The ratio of extractant to oil phase (w/w) may be 1:1 to 10:1.
Working up may be carried out, for example, by separation, more particularly by sedimentation and decantation, centrifugation, or coalescence separation using a separator.
Other possible working-up methods include removal of the solvent in vacuo at temperatures of <100° C. and preferably <80° C.
The following examples are illustrative of the invention and should not be construed as limiting in any manner whatsoever.
10 g mackerel oil and 10 g water were introduced into a flask and heated with stirring to 45° C. or 60° C. Various enzymes were then added in a quantity of at most 1% free enzyme (commercial enzyme preparation) or 3% immobilized enzyme, after which the mixtures were incubated with stirring. Samples were taken during the reaction and the conversion was determined by measurement of the acid value. From a conversion of >40% degree of hydrolysis the fatty acid composition of the fatty acids released was analyzed. The content of glyceride-bound omega-3-fatty acids (mainly EPA and DHA present) was calculated from these data. Enzymes which did not achieve a conversion of 40% over a reaction time of 24 h were not further evaluated. The content of omega-3 fatty acids in the starting oil was 37.6%.
Alcaligenes sp.
Aspergillus niger
Candida antarctica A
Candida antarctica A
Candida antarctica B
Candida antarctica B
Candida cylindracea
Candida rugosa
Pseudomonas fluorescens
Rhizomucor miehei
Rhizopus oryzae
Rhizopus niveus
Thermomyces lanugenosus
Thermomyces lanugenosus
Coupled with good hydrolysis activity, the lipases from the organism Candida (except for lipase B from Candida antarctica) and Alcaligenes above all showed good negative selectivity for PUFAs. Thermomyces lanugenosus lipase both in free and in immobilized form also showed good selectivity and, at the same time, a good hydrolysis rate. All the enzymes tested showed slight negative selectivity for PUFAs.
10 g menhaden oil and 10 g water were introduced into a flask and heated with stirring to 45° C. or 60° C. Various enzymes were then added in a quantity of at most 1% free enzyme (commercial enzyme preparation) or 3% immobilized enzyme, after which the mixtures were incubated with stirring. Samples were taken during the reaction and the conversion was determined by measurement of the acid value. From a conversion of >40% degree of hydrolysis, the fatty acid composition of the fatty acids released was analyzed. The content of glyceride-bound omega-3-fatty acids (mainly EPA and DHA present) was calculated from these data. Enzymes which did not achieve a conversion of 40% over a reaction time of 24 h were not further evaluated. The content of omega-3 fatty acids in the starting oil was 38.0%.
Alcaligenes sp.
Aspergillus niger
Candida antarctica A
Candida antarctica A
Candida antarctica B
Candida antarctica B
Candida cylindracea
Candida rugosa
Pseudomonas
fluorescens
Rhizomucor miehei
Rhizopus oryzae
Rhizopus niveus
Thermomyces
lanugenosus
Thermomyces
lanugenosus
Coupled with good hydrolysis activity, the lipases from the organism Candida (except for lipase B from Candida antarctica) and Alcaligenes above all showed good negative selectivity for PUFAs. Thermomyces lanugenosus lipase both in free and in immobilized form also showed good selectivity and an adequate hydrolysis rate. All the enzymes tested showed slight negative selectivity for PUFAs.
10 g tuna oil and 10 g water were introduced into a flask and heated with stirring to 45° C. or 60° C. Various enzymes were then added in a quantity of at most 1% free enzyme (commercial enzyme preparation) or 3% immobilized enzyme, after which the mixtures were incubated with stirring. Samples were taken during the reaction and the conversion was determined by measurement of the acid value. From a conversion of >40% degree of hydrolysis, the fatty acid composition of the fatty acids released was analyzed. The content of glyceride-bound omega-3-fatty acids (mainly EPA and DHA present) was calculated from these data. Enzymes which did not achieve a conversion of 40% over a reaction time of 24 h were not further evaluated. The content of omega-3 fatty acids in the starting oil was 39.6%.
Alcaligenes sp.
Aspergillus niger
Candida antarctica A
Candida antarctica A
Candida antarctica B
Candida antarctica B
Candida cylindracea
Candida rugosa
Pseudomonas fluorescens
Rhizomucor miehei
Rhizopus oryzae
Rhizopus niveus
Thermomyces lanugenosus
Thermomyces lanugenosus
Coupled with good hydrolysis activity, lipases from the organism Candida (except for lipase B from Candida antarctica) above all showed good negative selectivity for PUFAs. Thermomyces lanugenosus lipase both in free and in immobilized form also showed good selectivity and, at the same time, a good hydrolysis rate. All the enzymes tested showed slight negative selectivity for PUFAs. This selectivity is more pronounced with DHA-rich tuna oil than with the EPA-rich fish oils.
Batches of 100 mg CLA methyl ester (CLA=conjugated linoleic acid), 0.9 ml water and 15 Mg(OH)2 were each weighed into 16 Eppendorf cups. The reactions were initiated by addition of a lipase or esterase, as listed in the Table. The samples were incubated on a shaker at 30° C. After 5 h, quantities of 3 mg Mg(OH)2 and more lipase were added. The batches were incubated on the laboratory shaker for a total of 24 h at 30° C. After 24 h, the incubation was terminated. The batches were completely frozen without product separation. All batches were freeze-dried, the soaps formed were acid-ligested and the fatty acids released were extracted with iso-octane. After silylation, the fatty acids obtained were analyzed by gas chromatography. The conversions of the enzymatic hydrolases were determined by comparison of the peak areas of the free acids formed with mono-, di- and triglycerides still present.
Thermomyces
Candida antarctica B
Rhizomucor miehei
Candida antarctica A
Candida cylindracea
Rhizopus javanicus
Porcine pancreas
Aspergillus niger
Candida rugosa
Mucor javanicus
Pseudomonas fluorescens
Rhizopus oryzae
Pseudomonas sp.
Chromobacterium viscosum
Fusarium oxysporum
Penicilium camenberti
Result: All lipases showed activity under the alkaline reaction conditions. Most of the lipases tested achieved a degree of hydrolysis of >80%. Thermomyces lanugenosus lipase showed a particularly good activity/cost profile.
Batches of 10 g castor oil, 1.35 g zinc oxide and 50 g water were each weighed into 14 closable vessels. Various enzymes (see Table below) were added to the batches. The batches were incubated for 24 h at 30° C. in a shaking incubator. After termination of the reaction, a sample of the zinc ricinoleate formed was taken and the water phase was removed by centrifuging. The samples were analyzed by gas chromatography for their content of zinc soaps and glycerides. To this end, 20 mg of the zinc ricinoleate samples were incubated for 30 mins. at 80° C. with 1 ml BSTFA/MSTFA [6:1] mixture and then analyzed in a DB5 HT column. The results were evaluated via the peak area. Zinc soaps were analyzed in the form of the free acids. The content of ricinoleic acid in the castor oil used and hence in the zinc soaps formed amounted to about 88%. The zinc soaps are referred to simply as zinc ricinoleate in the following.
Thermomyces
Rhizomucor miehei
Candida antarctica B
Candida antarctica A
Aspergillus niger
Candida cylindracea
Fusarium oxysporum
Geotrichum candidum
Mucor javanicus
Penicilium roquefortii
Porcine Pancreas
Pseudomonas sp.
Rhizopus javanicus
Rhizopus oryzae
Result: Where castor oil was used, all the lipases tested showed a hydrolytic reaction under alkaline conditions through the presence of ZnO in the reaction mixture. From the above screening, lipases/esterases or phospholipases from Thermomyces, Rhizomucor, Candida cylindracea or rugosa, Fusarium, Geotrichum, Mucorand Rhizopus are particularly suitable for a one-step hydrolysis coupled with zinc soap formation. The list of hydrolases tested is by no means complete.
Batches of 1 g PUFA ethyl ester, 2 g iso-octane, 1 g water and 40 mg Ca(OH)2 were introduced into 10 stirred and closable vessels and stirred. The PUFA ethyl ester used had a total content of 69% eicosapentaenoic and docosahexaenoic acid. Quantities of 50 mg various commercial enzyme preparations from various organisms, as listed in the Table, were added to the batches. The batches were incubated with stirring for 24 h. After 5 h and 24 h, samples were taken and the iso-octane phase was separated by centrifuging from the aqueous phase and the solid phase consisting of calcium soaps. The iso-octane phase contained the unreacted ethyl esters which were analyzed by gas chromatography.
Thermomyces lanugenosus
Rhizomucor miehei
Candida cylindracea
Rhizopus javanicus
Porcine pancreas
Candida rugosa
Mucor javanicus
Pseudomonas fluorescens
Rhizopus oryzae
Fusarium oxysporum
Result: Under the reaction conditions selected, only Thermomyces lipase is capable of further enriching an already-enriched PUFA ethyl ester.
Batches of 5 g of the enriched PUFA ethyl ester from Example 6, 10 g iso-octane and 0.1 g Ca(OH)2 were each introduced into 2 reaction vessels. 1 g water was added to batch 1 and 5 g water to batch 2. The reaction was initiated by addition of 100 μl Thermomyces lanugenosus lipase (Lipozym TL 100, Novozymes). The batches were incubated with stirring for 48 h at room temperature. After 24 h and 48 h, samples were taken and the iso-octane phase was separated by centrifuging from the aqueous phase and the solid phase consisting of calcium soaps. The iso-octane phase contained the unreacted ethyl esters which were analyzed by gas chromatography.
Thermomyces lanugenosus lipase
Result: Good enrichment of the PUFA ethyl ester was achieved irrespective of the quantity of water added.
Batches of 20 g of a PUFA ethyl ester with a total content of 36.8% eicosapentaenoic acid and docosahexaenoic acid and 14 g Ca(OH)2 were each introduced into 5 reaction vessels. Iso-octane and water were added to the batches in variable quantities, as listed in the Table. The reaction was initiated by addition of 200 μl Thermomyces lanugenosus lipase (Lipozym TL 100, Novozymes). The batches were incubated with stirring for 48 h at room temperature. After 5 h, 24 h and 48 h, samples were taken and the iso-octane phase was separated by centrifuging from the aqueous phase and the solid phase consisting of calcium soaps. The iso-octane phase contained the unreacted ethyl esters which were analyzed by gas chromatography.
Result: A distinct enrichment of the PUFAs (EPA+DHA) in the ethyl ester phase was achieved in all batches. An increase in the water content in the hydrolysis mixture produced an increase in the hydrolysis rate and hence an improved enrichment per reaction time.
20 g of the PUFA ethyl ester from Example 8, 1.4 g Ca(OH)2 and 60 g water were introduced into a reaction vessel. The reaction was initiated by addition of 100 μl Thermomyces lanugenosus lipase (Lipozyrn TL 100, Novozymes). After a reaction time of 6 h, the mixture was extracted with 30 g iso-octane. After 30 mins. of extraction, the iso-octane phase was separated by centrifuging from the aqueous phase and the solid phase consisting of calcium soaps. The iso-octane phase contained the unreacted ethyl esters which were analyzed by gas chromatography. The extracted ethyl ester phase contained a total of 59.1% EPA and DHA.
| Number | Date | Country | Kind |
|---|---|---|---|
| 07006847.3 | Apr 2007 | EP | regional |
