Enrichment of EPA and DHA by enzymatic ethanolysis: Effects of lipases from Thermomyces lanuginosus, Rhizomucor miehei, Rhizopus oryzae and Candida antarctica

Abstract

This work attempts to achieve the enrichment of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in acylglycerols as well as biodiesel production by investigating the performance of various lipases in ethanolysis. The ethanolysis activities of five immobilized lipases in decreasing order were as follows: Lipozyme TL IM, Novozym 40086/Lipozyme RM IM, Novozym 435 and Rhizopus oryzae lipase immobilized on polypropylene (RO PP). EPA could be enriched to a certain content by Lipozyme TL IM, Novozym 40086, Lipozyme RM IM, and RO PP. The enrichment of DHA was achieved well by those four sn-1,3 regioselective lipases, and DHA contents in acylglycerols were the highest when Lipozyme TL IM and Novozym 40086 were used, reaching 2.87-fold and 2.81-fold of the initial content. However, Novozym 435 could not enrich EPA and DHA effectively. Fatty acid ethyl esters produced in this work contained abundant palmitic acid and palmitoleic acid, which could be ideal biodiesel considering their chain length. The competitive factors of five lipases towards DHA were all significantly higher than those towards EPA. When Lipozyme TL IM and Novozym 40086 achieved the maximum DHA contents, their DHA recoveries in acylglycerols reached 91.87% and 89.00%, respectively. The DHA recoveries were all significantly higher than the corresponding EPA recoveries in the reactions catalyzed by five lipases. Moreover, Lipozyme TL IM could be a potential lipase for the separation of EPA and DHA. This study may promote the full use of fish oil and broaden the application of lipases.