The enzymatic synthesis of glycerides from glycerol and oleic acid in organic solvent was studied, and the optimal conditions for glyceride synthesis by lipases were established. Of the commercially available lipases that were investigated, Candida rugosa lipase and porcine pancreas lipase resulted in the highest extent of esterification. Iso-octane and hexane were particularly useful organic solvents in glyceride synthesis. The water content in the reaction mixture was of primary importance. For C. rugosa lipase and porcine pancreas lipase, the optimal water contents were 5 and 1%, respectively. Candida rugosa lipase and porcine pancreas lipase manifested contrasting positional specificities in glyceride synthesis.Esters of glycerol with FA occur naturally in fats and oils, and they are widely used for edible and industrial purposes. The modification of fats and oils and the production of glycerides from glycerol and FA promise the development of new oil and fat compounds that possess new properties in comparison with the original materials. Conventional esterification of glycerol to produce MG, DG, and TG by chemical catalysts requires high temperatures and leads to dark-colored products and undesired by-products (1).Using enzymes to catalyze these reactions is superior to using conventional chemical methods owing to their mild reaction conditions, high catalytic efficiency, and inherent selectivity, which result in much purer products. The use of lipolytic enzymes to catalyze the esterification reaction has been investigated by many workers (2-8). Lipases are present in high activity in the reserve tissue of many oilseed plants (9). Some lipases catalyze only the hydrolysis reaction of fats and oils, whereas others show catalytic activity on both the hydrolysis and esterification reactions.In this study, the synthesis of glycerides from glycerol and oleic acid in organic solvent by lipases was studied, and the effects of process parameters such as organic solvents, water content, glycerol content, and temperature were investigated.
EXPERIMENTAL PROCEDURESMaterials. Nonspecific Candida rugosa lipase and 1,3-positional specific porcine pancreas lipase (PPL), oleic acid, and glycerol were purchased from Sigma Chemical Co. (St. Louis, MO). All solvents used in this work were of analytical grade and were obtained from Merck (Darmstadt, Germany).Esterification reaction. Reaction mixtures for glyceride synthesis from glycerol and oleic acid consisted of: glycerol, 2 g (about 20 mmol); oleic acid, 0.5 g (about 2 mmol); water, 150 µL; and n-hexane, 3 mL. Reaction mixtures were placed in 50-mL Erlenmeyer flasks with silicone-capped stoppers to prevent evaporation of the reactants. The reaction was started by the addition of 0.1 g lipase in the form of dry powder. The suspension that resulted was agitated on an orbital shaker at 200 rpm at 30°C. At various times during incubation, 0.2 mL of the reaction mixture was withdrawn and analyzed by TLC and GC.Estimation of the degree of synthesis. The reaction was stopped by add...