Novel lipase-catalyzed synthesis of structured lipids from DHA-enriched glycerides and capric acid.

Structured lipids were successfully synthesized via a novel two-step enzymatic process. In the first step, docosahexaenoic acid (DHA) was enriched from tuna oil in the glyceride fractions by consecutive lipase-catalyzed reactions, hydrolysis, and ethanolysis. Following these processes, the DHA concentration increased from 26.7 mol% in the initial tuna oil to 66.2 mol% in the glyceride fraction. DHA-enriched glycerides were isolated from the reaction mixture obtained after the consecutive enzyme reactions using molecular distillation. In the second step, capric acid was incorporated into the hydroxyl groups of glycerides, which comprise monoacylglycerol, diacylglycerol, and triacylglycerol, to synthesize structured lipids via lipase-catalyzed esterification under vacuum. The optimum conditions for the synthesis of structured lipids were a temperature of 60 °C, an enzyme loading of 5%, and a vacuum of 5 mmHg. Consequently, the triacylglycerol content increased from 17.8% in the DHA-enriched glycerides to 85.6% in the final product.