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In the study of enzyme catalyzed kinetic resolution of racemates, it is imperative to assay how the optical yield varies with chemical conversion. In this paper, a method using one-time injection to determine enantiomeric excess and conversion of the stereoselective esterification of racemic ibuprofen with n-butanol catalyzed by lipase was developed with a commercially available HPLC CSP column Regis(S, S) Whelk-01. In the linear range of detector, all peak areas of products and substrates are proportional to their concentrations. Because the total mole concentration remains unchanged (equal to the initial value of ibuprofen) in the reaction process, the conversion could be calculated from the peak areas, provided the ratio of response factors was known. The calibration curves of two ibuprofen enantiomers with racemic ibuprofen as external standard were overlapped, indicating fiR = fiS. By investigating the variation of peak areas of products and substrates against conversion (determined by external standard), the ratio of peak area-concentration response factor of ibuprofen butyl ester to that of unreacted ibuprofen was determined to be 1 through linear regressions, from which the conversion could be directly determined by the self normalization of the peak areas. With a mobile phase of IPA/hexane/HAc/triethylamine (15/85/0.2/0.05, V/V, flow rate 0.4 mL/min), the resolution of ibuprofen enantiomers was sufficient for precise enantiomeric purity determination.
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PMID:[Chiral HPLC determination of conversion and enantiomeric excess of enzyme catalyzed stereoselective esterification of racemic ibuprofen]. 1132 81

Lipase catalyzed esterification reactions between lactic acid and several fatty acids have been studied. Difficulties arise in esterifying lactic acid because of the potential for this substance to act both as an acyl donor and as a nucleophile. These difficulties were minimized via strategies which greatly increased the yield of the desired ester. Use of the companion fatty acid in excess with respect to lactic acid in an apolar solvent (n-hexane) in which the lactic is not completely dissolved has been employed to minimize the potential for lactic acid to act as an acyl donor in a self-polymerization reaction.Beneficial and sinergistic effects of both silica gel and molecular sieves on conversion to the desired product are described. However, careful control of the amount of molecular sieves used is required. This fact is a consequence of two opposing effects of this material: i.e. adsorption of both lactic acid and water from the reaction mixture. For reaction between caprylic and lactic acids, use of an excessive amount of enzyme reduces the extent of conversion to 2-O-caproyl-lactic acid.A very pure ester of the L-enantiomer (optical rotation of [alpha]D(25) = -23.5) can be prepared in n-hexane using a four fold excess of caprylic acid and Candida antarctica lipase. Optimum reaction conditions lead to 35% yield of 2-O-caproyl-lactic acid, a result which is close to the maximum yield that can be enantioselectively obtained from commercial grade lactic acid (68 mole per cent monomer).
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PMID:Part III. Direct enzymatic esterification of lactic acid with fatty acids. 1142 29

Enzymatic acidolysis of borage oil (BO) or evening primrose oil (EPO) with eicosapentaenoic acid (20:5n-3; EPA) was studied. Of the six lipases that were tested in the initial screening, nonspecific lipase PS-30 from Pseudomonas sp. resulted in the highest incorporation of EPA into both oils. This enzyme was further studied for the influence of enzyme load, temperature, time, type of organic solvent, and mole ratio of substrates. The products from the acidolysis reaction were analyzed by gas chromatography (GC). The highest incorporation of EPA in both oils occurred at 45-55 degrees C and at 150-250 enzyme activity units. One unit of lipase activity was defined as nanomoles of fatty acids (oleic acid equivalents) produced per minute per gram of enzyme. Time course studies indicated that EPA incorporation was increased up to 26.8 and 25.2% (after 24 h) in BO and EPO, respectively. Among the solvents examined, n-hexane served best for the acidolysis of EPA with both oils. The effect of the mole ratio of oil to EPA was studied from 1:1 to 1:3. As the mole ratio of EPA increased, the incorporation increased from 25.2-26.8 to 37.4-39.9% (after 24 h). The highest EPA incorporations of 39.9 and 37.4% in BO and EPO, respectively, occurred at the stoichiometric mole ratio of 1:3 for oil to EPA.
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PMID:Structured lipids via lipase-catalyzed incorporation of eicosapentaenoic acid into borage (Borago officinalis L.) and evening primrose (Oenothera biennis L.) oils. 1180 16

Enzymatic synthesis of monoglycerides by glycerolysis of oil and fats in microaqueous solvent-free media was investigated by using lipase from pseudomonus fluorescens (PFL). Initial eutectic point(IEP) was substituted for melt point of oil and fats in Critical Temperature Theory. By investigating the glycerolysis under different IEP, it is showed that there is a relationship between composition of the oils and the yield of monoglycerides: Y = -0.0006 X3 + 0.0592 X2 - 0.8909 X + 26.753(13% < X < 76.5%), here X is the contents(W/W) of saturated fatty acid residue (C16 + C18) in the oils, Y is the yield of monoglycerides at 40 degrees C. The optimum isothermal reaction conditions for a system which IEP is 40 degrees C are: 40 degrees C, 3%-4.5% (W/W) water in glycerol, dosage of lipase is 500 u/g oil when the mole ratio of glycerol to oil is 2.5:1. The highest yield of monoglycerides is 81.4% in 48 h by means of programming temperature reaction.
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PMID:[Enzymatic synthesis of monoglycerides in microaqueous media by using lipase from Pseudomonus fluorescens]. 1197 7

Lipases are extracellular peripheral proteins that act at the surface of lipid emulsions stabilized, typically, by phospholipids. At a critical composition lipase activity toward substrates in phospholipid monolayers is discontinuously switched on by a small increase in substrate mole fraction. This occurs in part because lipase binding is inhibited by phospholipids. Binding of the lipase cofactor, colipase, is also inhibited by phospholipids. The initial rate of colipase binding increases abruptly at a substrate mole fraction that is approximately half the critical composition for lipase activity and just above that in substrate-phospholipid complexes. Moreover, complex collapse areas show an approximately 1:1 correlation with phospholipid excluded areas determined from an analysis of colipase adsorption rates. Thus, complexes inhibit colipase binding rate. Additionally, the switching of lipase activity likely occurs when uncomplexed substrate becomes the majority species in the interface. Lipase substrates, e.g. diacylglycerols, are typically the same lipids generated in the cytoplasmic surface of the plasma membrane of stimulated cells. As colipase binding is nonspecific and complexes involving lipase substrates form on the basis of lipid-lipid interactions alone, complexes should form in the plasma membrane of stimulated cells and may regulate protein translocation to the membrane.
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PMID:Regulation of lipases by lipid-lipid interactions: implications for lipid-mediated signaling in cells. 1259 38

Screening of five commercially available lipases for the incorporation of capric acid (CA) into docosahexaenoic acid single cell oil (DHASCO) indicated that lipase PS-30 from Pseudomonas sp. was most effective. Of the various reaction parameters examined, namely, the mole ratio of substrates, enzyme amount, time of incubation, reaction temperature, and amount of added water, for CA incorporation into DHASCO, the optimum conditions were a mole ratio of 1:3 (DHASCO/CA) at a temperature of 45 degrees C, and a reaction time of 24 h in the presence of 4% enzyme and 2% water content. Examination of the positional distribution of fatty acids on the glycerol backbone of the modified DHASCO with CA showed that CA was present mainly in the sn-1,3 positions of the triacylglycerol (TAG) molecules. Meanwhile, DHA was favorably present in the sn-2 position, but also located in the sn-1 and sn-3 positions. The oxidative stability of the modified DHASCO in comparison with the original DHASCO, as indicated in the conjugated diene values, showed that the unmodified oil remained relatively unchanged during storage for 72 h, but DHASCO-based structured lipid was oxidized to a much higher level than the original oil. The modified oil also attained a considerably higher thiobarbituric acid reactive substances value than the original oil over the entire storage period. However, when the oil was subjected to the same process steps in the absence of any enzyme, there was no significant difference (p > 0.05) in its oxidative stability when compared with enzymatically modified DHASCO. Therefore, removal of antioxidants during the process is primarily responsible for the compromised stability of the modified oil.
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PMID:Synthesis of structured lipids via acidolysis of docosahexaenoic acid single cell oil (DHASCO) with capric acid. 1513 33

Structured triacylglycerols (ST) enriched in eicosapentaenoic acid (EPA) in position 2 of the triacylglycerol (TAG) backbone were synthesized by acidolysis of a commercially available EPA-rich oil (EPAX4510, 40% EPA) and caprylic acid (CA), catalyzed by the 1,3-specific immobilized lipase Lipozyme IM. The reaction was carried out in a packed bed reactor (PBR) operating in two ways: (1) by recirculating the reaction mixture from the exit of the bed to the substrate reservoir (discontinuous mode) and (2) in continuous mode, directing the product mixture leaving the PBR to a product reservoir. By operating in these two ways and using a simple kinetic model, representative values for the apparent kinetic constants (kX) for each fatty acid (native, Li or odd, M) were obtained. The kinetic model assumes that the rate of incorporation of a fatty acid into TAG per amount of enzyme, rX (mole/(h g lipase)) is proportional to the extent of the deviation from the equilibrium for each fatty acid (i.e., the difference of concentration between the fatty acid in the triacylglycerol and the concentration of the same fatty acid in the triacylglycerol once the equilibrium of the acidolysis reaction is reached). The model allows comparing the two operating modes through the processing intensity, defined as mLt/(V[TG]0) and mL/(q[TG]0), for the discontinuous and continuous operation modes, respectively. In discontinuous mode, ST with 59.5% CA and 9.6% EPA were obtained. In contrast, a ST with 51% CA and 19.6% EPA were obtained when using the continuous operation mode. To enhance the CA incorporation when operating in continuous mode, a two-step acidolysis reaction was performed (third operation mode). This continuous two-step process yields a ST with a 64% CA and a 15% EPA. Finally, after purifying the above ST in a preparative silica gel column, impregnated with boric acid, a ST with 66.9% CA and 19.6% EPA was obtained. The analysis by reverse phase and Ag+ liquid chromatography of the EPA-enriched ST demonstrated that the CA was placed in positions 1 and 3 and the EPA was occupying position 2 of the final ST.
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PMID:Production of structured lipids by acidolysis of an EPA-enriched fish oil and caprylic acid in a packed bed reactor: analysis of three different operation modes. 1529 28

Optically active form of alpha-cyano-3-phenoxybenzyl (CPB) alcohol, building block of pyrethroid insecticides, was synthesized as its acetate by the combination of anion-exchange resin (D301)-catalyzed transcyanation between m-phenoxybenzaldehyde (m-PBA) and acetone cyanohydrin (AC), and lipase (from Alcaligenes sp.)-catalyzed enantioselective transesterification of the resulting cyanohydrin with vinyl acetate. Through optimizing technological conditions, the catalyzing efficiency was improved considerably compared to methods previously reported. Concentrations of CPB acetate were determined by gas chromatograph. The enantio excess (e.e.) values of CPB acetate were measured by NMR (nuclear magnetic resonance) method. Effects of solvents and temperatures on this reaction were studied. Cyclohexane was shown to be the best solvent among the three tested solvents. 55 degrees C was the optimal temperature for higher degree of conversion. External diffusion limitation was excluded by raising the rotational speed to 220 r/min. However, internal diffusion could not be ignored, since the catalyst (lipase) was an immobilized enzyme and its particle dimension was not made small enough. The reaction rate was substantially accelerated when the reactant (m-PBA) concentration was as high as 249 mmol/L, but decreased when the initial concentration of m-PBA reached to 277 mmol/L. It was also found that the catalyzing capability of recovered lipase was high enough to use several batches. Study of the mole ratio of AC to m-PBA showed that 2:1 was the best choice. The strategy of adding base catalyst D301 was found to be an important factor in improving the degree of conversion of the reaction from 20% to 80%. The highest degree of conversion of the reaction has reached up to 80%.
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PMID:Optimization of technological conditions for one-pot synthesis of (S)-alpha-cyano-3-phenoxybenzyl acetate in organic media. 1568 1

China has richly and inexpensive fat and oils from animal and plants, but these resources could not get effectively utilization. In order to make the best of these resources, lipase-catalyzed acidolysis of lard with caprylic acid to produce functional lipid in solvent free system was investigated. Of the five lipases that were tested in the initial screening, immobilized lipase TL IM fromca T. languginosa resulted in the highest incorporation of capry lic acid into lard. This enzyme was further studied for the effect of enzyme load, substrate ratib, reaction time, reaction temperature and added water content on the incorporation of caprylic acid into lard. HPLC analyzed the products from the acidolysis reaction. The highest incorporation was attained at 20% enzyme load. Time course studied suggest that the incorporation of caprylic acid into lard was increased up to 38.77 mol% after 24h. Desirable mole ratio of substrates was 1:2 (lard: caprylic acid), caprylic acid incorporation up to 30.95 mol%. In the range of 45 - 60 degrees C , temperature had no significant effect on enzyme activity and caprylic acid incorporation changed little. When temperature was above 60 degrees C, incorporation of caprylic acid into lard was decreased. The highest incorporation of caprylic acid into lard 35.76 mol% was attained when added water content was 2.5%.
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PMID:[Production of functional lipids by lipase-catalyzed acidolysis of lard in solvent free system]. 1610 82

Lipase (triacylglycerol acylhydrolase [EC 3.1.1.3.]) was extracted from the microsomal fraction of cotyledons of dark grown seedlings of Canola (Brassica napus L. cv Westar) by treatment with Triton X-100. The enzyme was partially purified by chromatography on Sephacryl S-300 and DEAE Bio-Gel and was stable when stored at -20 degrees C in 50% (v/v) glycerol. The lipase aggregated readily but the distribution of species present in solution could be controlled by nonionic detergents. A species with an apparent M(r) of about 250,000 was obtained by gel filtration chromatography in the presence of 1% (v/v) Triton X-100. Lipase activity was optimal near neutral pH, and the reaction approached maximum velocity at a concentration of 0.5 to 1 millimolar emulsified triolein. The reaction rate responded linearly to temperature up to about 40 degrees C and the hydrolytic process had an activation energy of 18 kilocalories per mole. Microsomal lipase lost about 20% and 80% activity when heat-treated for 1 hour at 40 degrees C and 60 degrees C, respectively. At appropriate concentrations, the detergents Triton X-100, n-octyl-beta-d-glucopyranoside, (3-[(3-cholamidopropyl-O-dimethylammonio]-1-propanesulfonate, cetyl trimethylammonium bromide, and sodium dodecyl sulfate all inhibited lipase activity. n-Octyl-beta-d-glucopyranoside, however, was stimulatory in the 2 to 8 millimolar concentration range. The inhibitory effects of Triton X-100 were reversible.
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PMID:Properties of Solubilized Microsomal Lipase from Germinating Brassica napus. 1666 80


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