Lipase-catalyzed esterification of glycerol and n-3 polyunsaturated fatty acid concentrate in organic solvent

Enzymatic synthesis of glycerides from glycerol and n-3 polyunsaturated fatty acid in organic solvent was studied. Optimal conditions for glyceride synthesis by lipases were established. Of the commercially available lipases that were investigated, lipase PS-30 fromPseudomonas sp. and lipase IM-60 fromMucor miehei resulted in the highest extent of esterification. Isooctane and hexane were particularly useful organic solvents in glyceride synthesis. The water content in the reaction mixture was of primary importance. For lipase PS-30 and lipase IM-60, optimal water contents were 5 and 1%, respectively. Lipases PS-30 and IM-60 manifested contrasting positional specificities in glyceride synthesis. Glycerides containing predominantly eicosapentaenoic acid and docosahexaenoic acid can be easily synthesized.     

Lipase-catalyzed synthesis of kojic acid esters in organic solvents

Kojic acid is an inhibitor of bacteria, viruses, and fungi. It is used for inhibiting the browning effect of tyrosinase in the food and cosmetic industries. To improve its lipophilic properties, Pseudomonas cepacia lipase and Penicillium camembertii lipase were used for catalyzing the esterification of kojic acid to synthesize kojic acid monolaurate and kojic acid monooleate. These products showed a 69.5% inhibitory effect on tyrosinase in hydrophobic organic solvent. The yields of kojic acid esters were affected by enzymes, substrates, organic solvent, and temperature. Lauric and oleic acids were the best substrates for esterification among various fatty acids tested. CaCl₂ and MnCl₂ stimulate Pseudomonas cepacia lipasecatalyzed esterification by 7.0%. On the contrary, MgCl₂, SrCl₂, and ZnCl₂ inhibited the reaction. The best pH of buffer for lipase pretreatment was pH 6.0. Pseudomonas and Penicillium lipases can be reused for the synthesis of kojic acid esters. After reaction at 40°C for 10 d, the Penicillium and Pseudomonas lipases still retained 57.0% and 92.0% of their initial activities, respectively.     

Lipase-catalyzed esterification of oleic acid and methanol in hexane—A kinetic study

The kinetics of immobilized lipase-catalyzed esterification of oleic acid and methanol in hexane were investigated. The reaction follows Michaelis-Menton kinetics as observed from the relationship of initial rate of the reaction, both as a function of enzyme and of substrate concentration. Inhibition by excess of methanol has been identified. The kinetic constants have been measured for the reaction in the absence of any significant external diffusional limitations. The kinetics of the enzymatic reaction are suggested to agree with a Ping-Pong Bi Bi mechanism.     

Lipase-catalyzed esterification of lactic acid with straight-chain alcohols

Enzymatic synthesis of esters of lactic acid and straight-chain alcohols with different chain lengths (C₆–C₁₈) were investigated in batch reactions with hexadecanol (C₁₆) as the model alcohol. Cyclohexane was the best solvent for higher ester yields, and the best biocatalyst was the immobilized Candida antarctica lipase B (Novozym 435) as well as the textile-immobilized Candida sp. lipase. A method was established to obtain ester yields in the range of 71 to 82% for the different alcohols, and the most favorable conditions for the esterification reaction using Novozym 435 were an equimolar ratio of lactic acid to alcohol, each at a concentration of 120 mM each; a 50°C reaction temperature; 190 rpm shaking speed; and the addition of 100 mg molecular sieves (4 Å) for drying. The ester yield increased with increasing lipase load, and a yield of 79.2% could be obtained after 24 h of reaction at 20 wt% of Novozym 435. The immobilized Candida sp. lipase prepared in the laboratory also could be used to produce esters of lactic acid and straight-chain alcohols, but it had a much lower activity than Novozym 435 with a temperature optimum of 40°C.     

A comparison between lipase-catalyzed esterification of oleic acid with glycerol in monolayer and microemulsion systems

Lipase-catalyzed synthesis-esterification of oleic acid with glycerol-was carried out in L2 microemulsions and in monolayers. The microemulsions were based on isooctane as a nonpolar component and various water-glycerol mixtures as polar component. The substrate, oleic acid/sodium oleate, constituted the microemulsion surfactant. The lipase resides mainly in the water pools. Monolayers of oleic acid/sodium oleate were formed on subsolutions of glycerol and water, and the enzyme solution was injected under the compressed monolayers. Thus, the arrangement of the reactants at the oil-water interface of the microemulsion can be regarded as analogous to that at the airwater interface of the monolayer. The microemulsion structure was characterized by self-diffusion nuclear magnetic resonance. It was found that the higher the glycerol-to-water ratio, the lower are the water D-values. The reactions in microemulsions generally gave a low degree of oleic acid conversion. The yield increased with increasing glycerolto-water ratio. Monoglycerides were the main product, and no triglyceride could be detected. The monolayer experiments gave a somewhat higher degree of conversion, with tri- and diglycerides being the major reaction products. The reason why triglycerides are formed in monolayer experiments but not in microemulsions is believed to be due to an unfavorable partitioning of the diglyceride in the microemulsion systems. Once formed, the diglyceride will partition into the hydrocarbon domain and become inaccessible for reaction with the enzyme-O-acyl intermediate at the oil-water interface. In addition, the interfaces in the two systems are different. The monolayer interface is static, whereas the microemulsion interface is highly dynamic, and this difference may also influence the product patterns.     

Synthesis of propylene glycol monoesters of docosahexaenoic acid and eicosapentaenoic acid by lipase-catalyzed esterification in organic solvents

Propylene glycol monoesters (PGM) of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are potentially health-beneficial water-in-oil emulsifiers useful in the food industry. These esters were synthesized enzymatically to overcome the problems associated with chemical processes. The products were analyzed by gas chromatography. The immobilizedMucor miehei lipase was found to be the best enzyme for the synthesis of both propylene glycol monoesters of EPA and DHA among nine lipases tested. The anhydrous enzyme and hydrophobic organic solvents were favored for the production of both monoesters. The yields of monoesters were also affected by temperature, pH memory, fatty acid/propylene glycol ratio, and reaction time. The yields of PGMDHA and PGMEPA with 50 mM fatty acid and 225 mM propylene glycol as substrates in 1 mL solvent mixture (hexane/t-butyl alcohol=9:1), catalyzed by Lipozyme IM-20 (50 mg) at 40°C for 24 h, were 47 and 49 mM, respectively. The enzyme still retained over 60% of its original activity after 10 d of batch-type operation (1 d per cycle) at 40°C for the synthesis of both PGMDHA and PGMEPA.     

Lipase-catalyzed incorporation of oleic acid into melon seed oil

The ability of lipase PS30 (Pseudomonas sp.) to modify the fatty acid profile of melon seed oil by incorporation of oleic acid (18:1n-9) was investigated. The transesterification was carried out in hexane in an orbital shaking water bath at 55°C for 24 h with methyl oleate (70% pure) as acyl donor. Oleic acid content increased from 13.5% to 53%, and linoleic acid (18:2n-6) content decreased from 65% to 33%. The incorporation of oleic acid into melon seed oil by Pseudomonas sp. lipase helped balance the fatty acid profile of the oil in terms of monounsaturated (18:1n-9) and essential fatty acids (18:2n-6).     

Enzymatic esterification of glycerol I. Lipase-catalyzed synthesis of regioisomerically pure 1,3-sn-diacylglycerols

Regioisomerically pure 1,3-sn-diacylglycerols are conveniently prepared in high yields (>80%) and in large quantities by enzymatic esterification of glycerol in the presence of various 1,3-selective lipases(Chromobacterium viscosum, Rhizopus delemar, Rhizomucor miehei) and a variety of different acyl donors like free fatty acids, fatty acid alkyl esters and vinyl esters. All reactions are carried out in aprotic organic solvents of low water content, namelyn-hexane, diethyl ether or tBuOMe. The creation of an artificial interphase between the solvent-immiscible hydrophilic glycerol and the hydrophobic reaction media by the adsorption of glycerol onto a solid support prior to use was essential for the success of these transformations. The effects of reaction conditions and the regioselectivities of the lipases on the product yields are described in detail.     

Lipase‐catalyzed esterification of cinnamic acid and oleyl alcohol in organic solvent media

The esterification of cinnamic acid (CA) and oleyl alcohol (OA) in organic solvent media by immobilized lipase Novozym 435 was optimized in terms of selected parameters, including the logarithm of the 1‐octanol/water partition coefficient of the organic solvent (log P, 0.29–4.5), initial water activity (a_w, 0.05–0.75), agitation speed (0–200 rpm), temperature (35–65 °C) and ratio of substrates (CA/OA, 1.0:0.5–1.0:6.0). The results showed that the more hydrophobic solvent mixtures and lower initial a_w values resulted in a higher enzymatic activity and bioconversion yield. The most appropriate solvent medium and initial a_w value was the mixture of iso‐octane/2‐butanone (85:15, v/v) and 0.05, respectively. The results also showed that an agitation speed of 150 rpm and a reaction temperature of 55 °C were optimal for the reaction system. The activation energy (E_a) of the esterification reaction was calculated as 43.6 kJ mol^?1. The optimal ratio of CA to OA was 1.0:6.0, with the absence of any inhibition by OA. Using the optimized conditions, the maximum enzymatic activity was 390.3 nmol g^?1 min^?1, with a bioconversion yield of 100% after 12 days of reaction. In addition, the electrospray ionization‐mass spectroscopy analysis confirmed that the major end product of the esterification reaction was oleyl cinnamate. Copyright © 2005 Society of Chemical Industry     

Kinetic studies on immobilised lipase esterification of oleic acid and octanol

The present work investigates the reaction kinetics of immobilised lipase esterification of oleic acid and octanol, in a solvent-free system. Lipase from Rhizomucor miehei was immobilised on a hydrophobic support. The initial reaction rate was investigated as a function of octanol concentration and temperature, and the reaction kinetics were described in terms of the Michaelis–Menten mechanism. Evaluating K_m, V_max and k_cat/K_m as a function of temperature, it was found that K_m was minimum and k_cat/K_m was maximum at 40°C while V_max was maximum at 50°C. Furthermore, applying the Ping Pong Bi Bi mechanism yielded good results for this two-substrate system.     

Catalyzed esterification of oleic acid

Conclusions It has been shown that the effectiveness of certain divalent metal salts as esterification catalysts can be quantitatively compared and that for the Group II B series their effectiveness is inversely proportional to their ionic volume. The rates of esterification using these metal salts are not as great as for strong acids, but it is probable that the mechanism is similar and that the metal salts act as acids in the general sense. The rates of esterification differ appreciably for different primary polyols. It is also probable that these differences are related to the comparative acidity or basicity of the alcohols. It would be particularly desirable to investigate the activity of the catalysts in different alcohols. It is possible that infrared studies might show formation of a complex between the catalyst and either the alcohol or the acid or both. A number of possibilities may be formulated; at present we lack critical evidence to distinguish between them and this area provides a fruitful field for further research. Presented at the spring meeting, American Oil Chemists' Society, New Orleans, La., April 20–22, 1959.     

Lipase-catalyzed reactions involving thia fatty acids and ester derivatives

Enzymatic hydrolysis of synthetic methyl 5-, 9-, and 12-thiastearates in aqueous media withCandida cyclindracea or porcine pancreatic lipases gave the corresponding fatty acids in 70–100% yield. Hydrolysis of the 3- and 4-positional isomers gave only 15–25% of the free thia fatty acids, suggesting discrimination against these isomers by lipases. No lipolysis was achieved with methyl 2-thialaurate under a range of reaction conditions. Esterification of the 3-, 4-, 5-, 9-, and 12-thiastearic acids withn-butanol inn-hexane using Lipozyme (immobilizedRhizomucor miehei) as the biocatalyst gave the corresponding butyl esters in 80–95% yield. Interesterification (acyl exchange) of triolein with methyl 9-thiastearate in the presence of Lipozyme showed the incorporation of 9-thiastearoyl chain at only one of the α-positions of triolein. In the case of methyl 2-thialaurate, no lipase-catalyzed acyl exchange reaction was possible. This study showed that the position of the sulfur atom in thia fatty esters affects the lipase-catalyzed hydrolysis and interesterification reactions.     

Enzymatic esterification of glycerol II. Lipase-catalyzed synthesis of regioisomerically pure 1(3)-rac-monoacylglycerols

Regioisomerically pure 1(3)-rac-monoacylglycerols are conveniently prepared in high yields (>75%) and in multigram quantities by enzymatic esterification of glycerol in the presence of various lipases(Chromobacterium viscosum, Rhizopus delemar, Rhizomucor miehei) with a variety of different acyl donors, such as free fatty acids, fatty acid alkyl esters, vinyl esters and triacylglycerols, as well as natural fats and oils. All reactions are carried out in aprotic organic solvents with low water content, namelyn-hexane, diethyl ether, tBuOMe or mixtures of these solvents. Essential for the success of these transformations were the following two factors. First, the creation of an artificial interphase between the solvent-immiscible hydrophilic glycerol and the hydrophobic reaction medium by its adsorption onto a solid support. Second, a facile system for the separation of the desired monoacylglycerol from the reaction mixture, coupled with the continuous recycling of acyl donor and undesirable by-products.     

Esterification of oleic acid with glycerol in the presence of sulfated iron oxide catalyst

Esterification of oleic acid with glycerol was investigated in view of the reaction kinetics, using “superacidic” sulfated iron oxide catalysts. A series of different sulfate contents were prepared and characterized by a multitude of techniques prior to their use as catalysts. The sulfated iron oxide reaction was carried out with equivalent amounts of reactants in the temperature range of 180–240°C. Effects of the sulfate content and the catalyst amount on reaction kinetics at different temperatures were evaluated.     

Kinetics of lipase catalyzedenantioselective esterification of racemic ibuprofen in isooctane

The kinetics of Candida rugosa lipase catalyzed esteritlcation of racemic ibuprofen with n-butanol in isooctane was studied. The kinetic study was carried out with the addition of 0.1% and 2% (by volume) of water for enzyme activation respectively when celite was added into isooctane for enzyme dispersion. The specific initial rate for S-ibuprofen can be fitted with the Ping Pong Bi Bi mechanism with dead-end competitive inhibition by the alcohol. The time courses of the enantioselective esteriflcation of the two ibuprofen enantiomers with different initial substrate concentrations and water contents were simulated with a model in which both effects of enzyme inactivation by long term reaction and reversed hydrolytic reaction under high water content were taken into consideration.     

Lipase-catalyzed esterification of citronellol with lauric acid in supercritical carbon dioxide/co-solvent media

Direct esterification of citronellol and lauric acid catalyzed by immobilized lipase B from Candida antarctica was performed in supercritical carbon dioxide with different organic solvents and ionic liquids serving as co-solvents. The highest concentration of citronellol laurate after 1 h of reaction performance (3.95 mmol/g substrates) was obtained in SC CO₂ with ethyl methylketone serving as a co-solvent. The optimal temperature and pressure for citronellol laurate synthesis in SC CO₂/EMK medium was determined to be 60 °C and 10 MPa.     

Solvent polarity influences product selectivity of lipase-mediated esterification reactions in microaqueous media

Esterification reactions were evaluated by using lipases fromRhizomucor miehei (Lipozyme IM20) andPseudomonas cepacia (PS-30) with equimolar levels (1.77 mmol) of undecanoic acid and glycerol or 1,3-propanediol (1,3-PD) or 1,2-propanediol (1,2-PD) in organic solvents of log P (partition coefficient between 1-octanol/water) values of (−0.33–4.5. Reaction yields (percentage of esterified undercanoate) with glycerol ranged from 1.4 to 72%, with greatest yields observed in solvents of log P 4.0–4.5 for Lipozyme, whereas the PS-30 lipase was similarly effective (27–38% yield) over the full range of solvent polarities. For both enzymes, as solvent apolarity increased, so did the extent of acylation of glycerol in the final product mixture. Reaction yields with 1,3-PD ranged from 8.1 to 64% for Lipozyme and from 18 to 84% for PS-30 lipase, with greatest yields observed for both enzymes in solvents of log P values in the range 1.2–5.0. For both lipases, the shift to greater solvent apolarity was accompanied by an increased molar ratio of diacylated-1,3-PD/monoacylated-1,3-PD in the product mixture. Reaction yields with 1,2-PD ranged from 2.5 to 45% for Lipozyme and from 12 to 52% for PS-30 lipase, with greatest yields observed in solvents of log P values in the ranges 1.4–1.9 and 1.4–4.5, respectively. The shift to greater solvent apolarity was accompanied by an increased molar ratio of diacylated-1,2-PD: monoacylated-1,2-PD in the product mixture, except for Lipozyme in the three most apolar solvents (log P of 3.5–4.5) in which there was a general attenuation of activity. These results suggest the existence of a solvent polarity influence on reaction product selectivity in multiproduct reactions, which can be partially explained on the basis of differential solvation and extraction properties of solvents.     

表面活性剂包衣的固定化脂肪酶在有机介质中催化酯化反应

以大孔吸附树脂为载体,将来源于Candidarugosa的脂肪酶用吸附法固定化后用谷氨酸双十二烷基酯核糖醇进行包衣,用于在有机溶剂中催化月桂酸和月桂醇的酯化反应。结果表明,AB 8型大孔吸附树脂为最佳载体,最适有机溶剂为异辛烷,酶固定化后再包衣,酶的比活较未包衣前提高了60%—90%。     

Lipase-catalyzed synthesis of lysophosphatidylcholine using organic cosolvent for in situ water activity control

Lysophosphatidylcholines (LPC) were synthesized from l-α-glycerophosphatidylcholine (GPC) by lipase-catalyzed esterification in a solvent-free system. Adding small amounts of a water-mimicking solvent such as dimethylformamide (DMF) to the reaction media significantly enhanced the reaction rate and the product yield. The role of solvent was studied with regard to changes in substrate solubility, the water activity of the reaction system, and the water content of the enzyme. Whereas the solubility of GPC was virtually unaffected by the addition of DMF at controlled water activity, it was considerably affected by water activity. DMF itself lowered the water activity of the system and deprived Lipozyme IM of water. The LPC production was also controlled by varying the initial water content of the enzyme. When two kinds of controls were employed together, a synergistic effect was observed and a 90% conversion was achieved. As a result, an operating window was suggested for LPC production, including water activity of Lipozyme IM and concentration of DMF as two parameters.     

Enzymatic esterification of dihydroxystearic acid

Dihydroxystearic acid (DHSA) ester was synthesized enzymatically to overcome the problems associated with chemical processes. Immobilized enzyme, Lipozyme IM and Novozym 435, were employed as catalysts in the esterification reaction between DHSA and monohydric alcohol. Various factors that may affect the esterification reaction were studied, such as initial water content (a _w ), organic solvent, substrate concentration and the influence of alcohol chain length. It was found that the percent conversion was higher in organic solvents with log P (the logarithm of the partition coefficient of solvent in octanol/water system) from 2.0 to 4.0. The reaction was not affected by a _w from 0.09 to 0.96. Increasing the mole ratio of alcohol to acid above 2.0 did not increase the percent converions of ester. The ester was identified by Fourier transform infrared and ¹³C nuclear magnetic resonance spectroscopy.