Concentration of docosahexaenoic acid from tuna oil via a two lipase-catalyzed reaction.

Docosahexaenoic acid (DHA) was concentrated successfully in the glyceride fractions from tuna oil via a two-step enzyme reaction involving hydrolysis and ethanolysis. In the first step, Candida rugosa lipase-catalyzed hydrolysis was carried out to concentrate DHA in the glyceride fractions. The DHA content in the glyceride fraction after hydrolysis increased from 30% in the initial tuna oil to 46%. In the second step, Lipozyme RM IM-catalyzed ethanolysis was conducted with the reaction mixture from the first step to further concentrate DHA in the glyceride fraction. In this step, the reaction mixture obtained from the first step was employed directly in Lipozyme RM IM-catalyzed ethanolysis without additional steps needed to remove free fatty acid. Finally, DHA was concentrated from an initial content of 30% in the tuna oil to 68.4% in the glyceride fractions via a novel two-step enzyme reaction strategy.