Concentration of docosahexsaenoic acid from tuna oil by a combination of solvent crystallization and lipase-catalyzed ethanolysis

Abstract

The docosahexaenoic acid (DHA) was concentrated from tuna oil fatty acid using solvent crystallization combined with lipase-catalyzed ethanolysis. In the first step, solvent crystallization was carried out to concentrate DHA from tuna oil fatty acid using acetonitrile as a solvent. The optimal conditions of solvent crystallization were the crystallization temperature of −40°C and the fatty acid to solvent ratio of 1:8 (w/v). This step increased the DHA content in the original tuna oil fatty acid from 22% up to 61%. In the second step, lipase-catalyzed ethanolysis was conducted with DHA-enriched fatty acid from the first step using Lipozyme RM IM (from Rhizomucor miehei) as a biocatalyst. The optimum conditions of this second step were the reaction temperature of 20°C and the molar ratio of 1:1 (fatty acid to ethanol). Overall, DHA enrichment with purity of 85% was obtained by the two step processes.