Synthesis of DHA-enriched triglyceride through glycerolysis: Process parameters and reuse of partially inactivated lipase

Docosahexaenoic acid (DHA)-enriched triglyceride products are valued by pharmaceutical and health and wellness industry. Enzymatic synthesis is an efficient method for producing DHA-enriched triglyceride. In this presented study, enzymatic synthesis conditions were optimized as follows: molar ratio of DHA ethyl ester (DHA-EE) to glycerol 3:1; lipase loading 6.4% (with respect to the DHA-EE mass); reaction temperature 108 °C; reaction time 13.6 h. Under these conditions, the yield of triglyceride reached 97.00 ± 0.61%. Catalytical activity of lipase reduced to 80% after 10 cycles, which was defined as inactivated lipase. Increasing lipase loading to 8.0% (catalytical activity equal to original lipase) can’t convert DHA-EE to triglyceride. However, DHA triglycerides can be achieved by using 4.0% inactivated lipase plus 3.2% original lipase (catalytical activity equal to original lipase). Analysis of the reaction kinetics showed that inactivated lipase cannot reach the activation energy (47.94 kJ/mol) required for the reaction system, but inactivated lipase plus original lipase can. A triglyceride content of 95.44 ± 0.54% was achieved using 4.0% inactivated lipase plus 3.2% original lipase, which was no significant difference with original lipase. This present study provided a technical solution to reuse the partially inactivated lipase and may reduce the prime cost of producing DHA-enriched triglyceride. • DHA-enriched triglyceride was synthesized by partially inactivated lipase plus original lipase. • The reaction condition was optimized using response surface. • Analysis of the reaction kinetics showed that the inactivated lipase tended to synthesize mono- and diglycerides. • This present study provides a technical solution to reuse the partially inactivated lipase.