Acyl Group Migrations in 2-Monoolein

Acyl migration in 2-monoolein dissolved in solvents under conditions common in lipid modification reactions has been studied. The effects on acyl migration of solvent, incubation temperature, water activity, polar additives and solid additives have been investigated. Extensive acyl migration occured in aliphatic hydrocarbons and water-miscible alcohols under dry conditions. The acyl migration rate could be decreased in several nonpolar solvents by adding a small amount of water or an alcohol. Increasing water activity had no effect in isooctane, but decreased the acyl migration rate dramatically in methyl tert-butyl ether and methyl isobutyl ketone. Several commonly used enzyme supports catalysed acyl migration, showing that supports with surface charges could catalyse acyl migration.     

Studies on the lipozyme-catalyzed synthesis of butyl laurate

The effects of temperature, speed of agitation, enzyme concentration, etc., on butyl laurate synthessis using Mucor miehei lipase (Lipozymetrade mark) have been studied. Although the soluble enzyme was quite thermcstable in aqeous solution, it deactivated rapidly at and above 40 degrees C in the presence of butanol. This enzyme immobilized on an anion-exchange resin (Lipozymetrade mark) showed enhanced stability (as compared to the soluble form) to denaturation by butanol under the same conditions. The denaturation of M. miehei lipase was found to be a function of the butanol concentration in the aqueous phase, and rapid denaturation takes place at the concentration corresponding to its saturation at that temperature. (c) 1995 John Wiley & Sons, Inc.     

Conversion of Soybean Oil to Biodiesel Fuel Using Lipozyme TL IM in a Solvent-free Medium

The conversion of soybean oil to biodiesel fuel was investigated in the presence of a lipase from Thermomyces lanuginosus (commercially called Lipozyme TL IM) in a solvent-free medium. The lipase was inactivated when more than 1.5 molar equivalent of methanol was added to the oil mixture. To fully convert the oil to its corresponding methyl esters, the reaction was performed successfully by a three-step addition of 1 molar equivalent of methanol and under the optimized conditions (40°C, 150 rpm, 10% enzyme quantity based on oil weight), the maximum methyl ester (ME) yield was 98% after 12 h reaction. By-product glycerol had a negative effect on enzymatic activity and iso-propanol was found to be effective for glycerol removal, in the presence of which lipase expressed relatively high activity and more than 94% of the ME yield was maintained after being used repeatedly for 15 batches.     

Biocatalysed synthesis of sn-1,3-diacylglycerol oil from extra virgin olive oil

Enzymatic synthesis of sn-1,3-diacylglycerols (sn-1,3-DAG) in two steps without isolation of the intermediates was investigated. Firstly ethanolysis of extra virgin olive oil (EVO) using immobilized non-regiospecific lipase from Candida antarctica (Novozym 435) was carried out to obtain glycerol (Gly) and fatty acid ethyl esters (FAEE). In the second step the ethanolysis products have been re-esterificated testing different sn-1,3-regiospecific lipases, both immobilized and non-immobilized, in different reaction media, that is in the presence of solvents or in a solvent-free system, for different times, at different temperatures (12, 25 and 40 °C). The lipase from Rhizomucor miehei (Lipozyme IM) has been the most effective among the sn-1,3-specific lipases screened.     

Influence of water activity on the synthesis of triolein catalyzed by immobilized Mucor miehei lipase

The influence of the thermodynamic activity of water (a(w))on the synthesis of triolein catalyzed by Mucor miehei lipase was investigated. Its effect on the equilibrium and on the rates of the different reactions present, esteification and mono- and diglyceride isomerization, was evaluated through measurements made in controlled water activity atmosphere. The apparent equilibrium constants were measured from the concentration of the different species as a function of the intial glycerol-to oleic-acid ratio using all the values at once with a multi-response nonlinear regression technique. Rate constants were determined from kinetic measurements and non-linear regression uning the variation of the concentration of all significant species in the system. Except for the synthesis of diolein from monoolein, which shows a maximum for a(w) approximately 0.5, the apparent rate constants of the various reactions are not significantly affected by the value of the water activity. The equilibrium is shifted to-ward the synthesis of triolein for low values of a(w), indicating that in the design of a process for triglyceride synthesis, using M. miehei lipase as a catalyst, the water activity can be lowered to extreme values to favor the synthesis, without any sacrifice on the productivity of the process. (c) 1995 John Wiley & Sons, Inc.     

Kinetic study of the lipase-catalyzed synthesis of triolein

The kinetics of the synthesis of triolein catalyzed by immobilized Mucor miehei lipase were studied. Equilibrium constants for the synthesis of mono-, di-, and triolein were calculated from the equilibrium compositions for different initial ratios of glycerol and oleic acid by means of multiresponse regression. The 1,3-specific lipase can catalyze the synthesis of triolein because the ester enzymatically formed with the primary alcohol isomerizes, through acyl migration, to an ester on the secondary hydroxyl. The freed primary hydroxyl may then undergo further enzymatic conversion. The rates of isomerization depend on the concentration of oleic acid. (c) 1993 Wiley & Sons, Inc.     

Production of structured lipids by lipase-catalysed interesterification in an ultrafiltration membrane reactor

The application of membranes to the enzymatic production of structured lipids has been investigated using an ultrafiltration membrane reactor for a reaction between medium chain triacylglycerols (MCT) and n-3 polyunsaturated fatty acids from fish oil. Lipozyme IM was used as the biocatalyst. The incorporation of polyunsaturated fatty acids into MCT was increased by about 15% over 80 h by simultaneous separation of the released medium chain fatty acids compared to control.     

脂肪酶催化猪油与辛酸酸解制备功能性脂反应条件的优化

目的:探索有机溶剂体系中酶法酸解猪油与辛酸制备减热量型功能性脂的最佳反应条件。方法:采用响应曲面法中的3水平5因子2星点部分因子试验设计,评价酸解反应中的5个关键因素,即酶量、反应时间、反应温度、底物比率和水分添加量及其交互作用对辛酸插入率的影响,确定最佳反应条件。结果:建立了辛酸插入率对5个变量的一个2次多项式数学模型,该模型极显著(P<0.0001),拟合优度良好。通过主效应分析,得出每个因子对模型的贡献程度从大到小依次为反应温度(负效应)>底物比率>反应时间>酶量(在实验范围内,水分不影响辛酸插入率)。借助模型方程产生的等高线图及统计软件,分析得出最大辛酸插入率下各个因子的最适水平分别为酶量16%,反应时间36h,反应温度50℃,底物比率3.8,水分添加量5%。在此条件下辛酸插入率达到了50.5mol%,与模型预测值50.7mol%非常吻合。结论:应用响应曲面法对有机溶剂体系中酶法酸解猪油与辛酸制备减热量性脂的反应条件进行优化是合理可靠,科学迅速的,且有效的。     

Chemo-enzymatic preparation of copolymeric polythioesters containing branched-chain thioether groups

Branched-chain copolymeric polythioesters (PTE) were formed in good yield (∼87%) by chemoenzymatic reactions including thiyl radical-induced addition of 1,6-hexanedithiol to the >C=C< double bond of dimethyl 1,18-octadec-9-enedioate and transthioesterification of polyfunctional dimethyl 1,18-octadec-9-enedioate with bifunctional 1,6-hexanedithiol catalyzed by immobilized lipase from Rhizomucor miehei. The reactions were performed in vacuo at 80°C without a solvent. PTE was extracted from the reaction mixture using methyl-t-butylether and precipitated from i-hexane. The polymer structure of the i-hexane-insoluble PTE precipitate was elucidated by GPC/SEC showing an average molecular mass (M _w) of 1,857 Da corresponding to a molecular weight range of up to 24,000 Da and a maximum degree of polymerization of up to 50 monomer units. Chemical derivatization with TMSH demonstrated the formation of up to ∼58 mol% of a branched-chain thio(S)ether, i.e., dimethyl S-9-(6-mercaptohexylthio)-1,18-octadecanedioate, and small proportions (∼8 mol%) of a dimeric disulfide formed therefrom. The chemical structures of various low-molecular weight (<900 Da) reaction products formed by transthioesterification, addition reaction or disulfide formation of the reactants or reaction intermediates, e.g., 1,18-octadec-9-enedioic acid methyl(O)ester 6′-S-mercaptohexyl thio(S)ester, dimethyl S-9-(6-mercaptohexylthio)-1,18-octadecanedioate, were elucidated by GC–MS. Similarly, dimethyl S-9-(6-S-methylthiohexylthio)-1,18-octadecanedioate and dimethyl 11,18,19,26-tetrathia-10,27-di-(7-carboxymethyl-heptyl)hexatriacontane-1,36-dioate were detected in the reaction mixtures after derivatization with trimethylsulfonium hydroxide.     

Enzymatic deacylation of l,2-diacyl-sn-glycero-3-phosphocholines to sn-glycerol-3-phosphocholine

This research was undertaken to study the enzymatic deacylation of l,2-diacyl-sn-glycero-3-phosphocholines (sn-1,2-PC) to sn-glycerol-3-phosphocholine (GPC); this compound could be an useful intermediate in the synthesis of “structured” sn-1,2-PC, after re-acylations of the two sn-positions of the glycerol backbone. The enzymatic reactions represent a valid alternative to the chemical deacylation that can be simply obtained in alkaline conditions. High conversion were achieved using a lipase selective for the sn-1-position of sn-1,2-PC (Lipozyme IM, from Mucor miehei) together with a Phospholipase A₂ from hog pancreas, enzyme selective for the sn-2-position; the best results were obtained carrying out the enzymatic reaction in a microemulsion system.