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 c atalysts for producing concentrates of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from fish oil as an alternative to convent ional chemical procedures. Transesterification of fish oil with ethano l was conducted under anhydrous solvent-free conditions with a stoichi ometric amount of ethanol. Among the 17 lipases tested, the results sh owed thai Pseudomonas lipases bad the highest activity toward the satu rated and monounsaturated fatty acids in the fish oil, much lower acti vity toward EPA and DHA and, at the same time, good tolerance toward t he anhydrous alcoholic conditions. With 10 wt% of lipase, based on wei ght of the fish oil triacylglycerol substrate (15% EPA and 9% DHA init ial 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 monounsat urated fatty acids reacted, leaving the long-chain n-3 polyunsaturated fatty acids unreacted in the residual mixture as mono-, di-, and tria cylglycerols. This mixture comprised approximately 50% EPA + DHA. Tota l 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 subst rate, was most unusual because most lipases favor EPA.