Steryl and stanyl esters of fatty acids by solvent-free esterification and transesterification in vacuo using lipases from Rhizomucor miehei, Candida antarctica, and Carica papaya.

Sitostanol has been converted in high to near-quantitative extent to the corresponding long-chain acyl esters via esterification with oleic acid or transesterification with methyl oleate or trioleoylglycerol using immobilized lipases from Rhizomucor miehei (Lipozyme IM) and Candida antarctica (lipase B, Novozym 435) as biocatalysts in vacuo (20-40 mbar) at 80 degrees C, whereas the conversion was markedly lower at 60 and 40 degrees C. Corresponding conversions observed with papaya (Carica papaya) latex lipase were generally lower. High conversion rates observed in transesterification of sitostanol with methyl oleate at 80 degrees C using Lipozyme IM were retained even after 10 repeated uses of the biocatalyst.

In vitro test for the effectiveness of antioxidants as inhibitors of thiyl radical-induced reactions with unsaturated fatty acids.

Attacks of thiyl radicals on the double bonds of unsaturated fatty acids lead to stereomutation (cis-, trans-isomerization without double-bond migration) and addition reactions (thioether formation). On the basis of these findings, an in vitro test system has been developed which allows the study of the effectiveness of specific antioxidants in preventing thiyl radical-induced attacks on unsaturated fatty acids. The test involves thermal treatment of a mixture of oleic (cis-9-octadecenoic) acid and 1-tetradecanethiol with the antioxidant, followed by measurement of the extent of formation of the products of stereomutation and addition (i.

High-yield preparation of wax esters via lipase-catalyzed esterification using fatty acids and alcohols from crambe and camelina oils.

Fatty acids obtained from seed oils of crambe (Crambe abyssinica) and camelina (Camelina sativa) via alkaline saponification or steam splitting were esterified using lipases as biocatalysts with oleyl alcohol and the alcohols derived from crambe and camelina oils via hydrogenolysis of their methyl esters. Long-chain wax esters were thus obtained in high yields when Novozym 435 (immobilized lipase B from Candida antarctica) and papaya (Carica papaya) latex lipase were used as biocatalysts and vacuum was applied to remove the water formed. The highest conversions to wax esters were obtained with Novozym 435 (> or =95%) after 4-6 h of reaction, whereas with papaya latex lipase such a high degree of conversion was attained after 24 h.

Papaya (Carica papaya) lipase with some distinct acyl and alkyl specificities as compared with microbial lipases.

Lipase from papaya (Carica papaya) latex (CPL), Candida antarctica lipase B (Novozym 435, NOV) and Rhizomucor miehei lipase (Lipozyme IM 20, LIP) were used as biocatalysts for the esterification of caprylic acid with straight-chain saturated C(4)-C(18) alcohols and unsaturated C(18) alcohols, such as cis-9-octadecenyl (oleyl, C(18:1), n-9), cis-6-octadecenyl (petroselinyl, C(18:1), n-12), cis-9,cis-12-octadecadienyl (linoleyl, C(18:2), n-6), all-cis-9,12,15-octadecatrienyl (alpha-linolenyl, C(18:3), n-3) and all-cis-6,9,12-octadecatrienyl (gamma-linolenyl, C(18:3), n-6) alcohols. With CPL, highest activity was found in the esterification of octanol and decanol, whereas both NOV and LIP showed a broad chain-length-specificity for the alcohols. CPL, as opposed to the microbial lipases, strongly discriminated against all the saturated long-chain ( > C(12)) and unsaturated C(18) alcohols.

Fatty acid steryl, stanyl, and steroid esters by esterification and transesterification in vacuo using Candida rugosa lipase as catalyst.

Sterols (sitosterol, cholesterol, stigmasterol, ergosterol, and 7-dehydrocholesterol) and sitostanol have been converted in high to near-quantitative yields to the corresponding long-chain acyl esters via esterification with fatty acids or transesterification with methyl esters of fatty acids or triacylglycerols using lipase from Candida rugosa as biocatalyst in vacuo (20-40 mbar) at 40 degrees C. Neither organic solvent nor water is added in these reactions. Under similar conditions, cholesterol has been converted to cholesteryl butyrate and steroids (5alpha-pregnan-3beta-ol-20-one or 5-pregnen-3beta-ol-20-one) have been converted to their propionic acid esters, both in moderate to high yields, via transesterification with tributyrin and tripropionin, respectively.

Antioxidants eliminate stereomutation and thioether formation during lipase-catalyzed thioesterification and transthioesterification for the preparation of uniform cis- and trans-unsaturated thioesters.

The lipase-catalyzed preparation of acyl thioesters from unsaturated fatty acids and alkanethiols is accompanied by the formation of geometrical isomers via stereomutation and of thioether derivatives via addition at the olefinic bond, both induced by thiyl radicals. Therefore, a method was developed in order to inhibit radical generation by the addition of antioxidants and thus prevent the formation of geometrical isomers and thioether derivatives during the lipase-catalyzed preparation of unsaturated acyl thioesters. In the presence of antioxidants such as 2,6-di-t-butyl-4-methylphenol (BHT) and octyl gallate thioesterification of oleic and elaidic acids with 1-tetradecanethiol as well as transthioesterification of methyl linoleate with 1-tetradecanethiol led to the corresponding geometrically uniform thioesters without radical-induced side reactions.

Specificity of papaya lipase in esterification with respect to the chemical structure of substrates.

Esterification, catalyzed by papaya (Carica papaya) lipase (CPL), was studied with various alcohols and carboxylic acids under competitive conditions. Acids studied were straight-chain saturates of different chain lengths, with octanoic acid as the reference. Alcohols chosen were aliphatic straight-chain, branched, secondary, tertiary, terpene, and aromatic alcohols of different chain lengths, using 1-hexanol as the reference.

Substrate selectivity of various lipases in the esterification of cis- and trans-9-octadecenoic acid.

The substrate selectivity of numerous commercially available lipases from microorganisms, plants and animal tissue towards 9-octadecenoic acids with respect to the cis/trans configuration of the C=C double bond was examined by the esterification of cis- and trans-9-octadecanoic acid (oleic and elaidic acid respectively) with n-butanol in n-hexane. A great number of lipases studied, e.g.

Solubilization and partial purification of constituents of acyl-CoA elongase from Lunaria annua.

All the constituent enzymes of acyl-CoA elongase, i.e., beta-ketoacyl-CoA synthase, beta-ketoacyl-CoA reductase, beta-hydroxyacyl-CoA dehydrase and trans-2-enoyl-CoA reductase, have been solubilized from a 15,000 x g particulate fraction from developing seeds of honesty (Lunaria annua) using Triton X-100.

Biotransformation of alkylglycerols in plant cell cultures: production of platelet activating factor and other biologically active ether lipids.

Plant cells in culture are capable of incorporating exogenous 1-O-alkyl-sn-glycerols into various neutral and ionic ether lipids. 1-O-Alkyl-2-acyl-sn-glycero-3-phosphocholines, the major class of compounds thus formed, are used for the preparation of platelet activating factor (PAF) in high yields. Similarly, the prochiral 2-O-alkyl-sn-glycerols are transformed to chiral 2-O-alkyl glycerophospholipids from which compounds can be obtained that exhibit antiviral activity in plant and animal cells.

Biosynthesis of triacylglycerols containing very long chain monounsaturated acyl moieties in developing seeds.

Particulate (15,000g) fractions from developing seeds of honesty (Lunaria annua L.) and mustard (Sinapis alba L.) synthesize radioactive very long chain monounsaturated fatty acids (gadoleic, erucic, and nervonic) from [1-(14)C]oleoyl-CoA and malonyl-CoA or from oleoyl-CoA and [2-(14)C]malonyl-CoA.

Lipase from Brassica napus L. discriminates against cis-4 and cis-6 unsaturated fatty acids and secondary and tertiary alcohols.

Lipase (EC 3.1.1.

Assay for triacylglycerol lipase by a rapid thin-layer chromatographic technique.

A rapid and accurate assay for lipase-catalyzed hydrolysis of radioactively labeled triacylglycerols has been developed. Aliquots of reaction mixtures are applied directly, i.e.

Biosynthesis and biotransformation of ether lipids.

Some naturally occurring as well as synthetic ether lipids are biologically active. In certain cases, the effects of these substances are enhanced, in others, they are inhibited by compounds that were isolated from natural sources or prepared by chemical synthesis. The biotransformation of natural or "unnatural" ether lipids in microorganisms, plant or animal tissue also can lead to substances that elicit biological effects.

Lipid biosynthesis in developing mustard seed: formation of triacylglycerols from endogenous and exogenous Fatty acids.

Cotyledons of developing mustard (Sinapis alba L.) seed have been found to synthesize lipids containing the common plant fatty acids and very long-chain monounsaturated (icosenoic, erucic, and tetracosenic) and saturated (icosanoic, docosanoic, and tetracosanoic) fatty acids from various radioactive precursors. The in vivo pattern of labeling of acyl lipids, either from fatty acids synthesized ;endogenously' from radioactive acetate or malonate, or from radioactive fatty acids added ;exogenously', indicates the involvement of the following pathways in the biosynthesis of triacylglycerols.