Enrichment of docosahexaenoic acid from fish oil by two step enzyme reactions

Abstract: Docosahexaenoic acid (DHA) is one of important polyunsaturated fatty acids in human. Many medical studies demonstrated that this fatty acid has various biological activities, such as improved cardiovascular and immune functions and reduction of cancer, and diabetes. In this study, we enriched DHA from the tuna oil with 30% DHA content via a two-step enzyme reaction, hydrolysis and ethanolysis. Two different lipases, which are Lipase OF (from Candida rugosa) and Lipozyme RM IM (from Rhizomucor miehei), were employed for the hydrolysis and the ethanolysis, respectively. In the first step, Lipase OF-catalyzed hydrolysis was carried out to enrich DHA in the glyceride fraction containing monoglyceride, diglyceride, and triglyceride. The DHA content in the glyceride fraction was approximately 50% after hydrolysis. In the second step, Lipozyme RM IM-catalyzed ethanolysis with the reaction mixture from the first step was carried out to further enrich DHA in the glyceride fraction. The reaction mixture employed in this reaction was directly used in the ethanolysis without any additional step for the removal of free fatty acid. After the ethanolysis, we obtained the enrichment with ca. 70% DHA content under the optimum conditions.