The preparation of concentrates of eicosapentaenoic acid and docosahexaenoic acid by lipase-catalyzed transesterification of fish oil with ethanol

The objective of this study was to investigate the use of lipases as catalysts for producing concentrates of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from fish oil as an alternative to conventional chemical procedures. Transesterification of fish oil with ethanol was conducted under anhydrous solvent-free conditions with a stoichiometric amount of ethanol. Among the 17 lipases tested, the results showed thai Pseudomonas lipases bad the highest activity toward the saturated and monounsaturated fatty acids in the fish oil, much lower activity toward EPA and DHA and, at the same time, good tolerance toward the anhydrous alcoholic conditions. With 10 wt% of lipase, based on weight of the fish oil triacylglycerol substrate (15% EPA and 9% DHA initial content), a 50% conversion into ethyl esters was obtained in 24 h at 20 degrees C, in which time the bulk of the saturated and monounsaturated fatty acids reacted, leaving the long-chain n-3 polyunsaturated fatty acids unreacted in the residual mixture as mono-, di-, and triacylglycerols. This mixture comprised approximately 50% EPA + DHA. Total recovery of DHA and EPA was high, over 80% for DHA and more than 90% for EPA. The observed fatty acid selectivity, favoring DHA as a substrate, was most unusual because most lipases favor EPA.