Selective hydrolysis of polyunsaturated fatty acid-containing oil with Geotrichum candidum lipase

Polyunsaturated fatty acids (PUFA), especially docosahexaenoic acid (DHA) acid eicosapentaenoic acid (EPA), can be concentrated in glycerides by hydrolyzing tuna oil with Geotrichum candidum lipase, the main components in the resulting oil being triglycerides. The reaction mechanism of this selective hydrolysis was investigated. Although the lipase acted well on the esters of oleic, linoleic, and alpha-linolenic acids, it did not affect the esters of gamma-linolenic acid, arachidonic acid, EPA, and DHA as much. The action of PUFA-glycerides was mono- > di- > triglycerides. Furthermore, the condensation of PUFA-partial glycerides and PUFA occurred even in the presence of a large amount of water, and the partial glycerides converted to the triglycerides by transacylation. These results suggested that the PUFA-rich triglycerides were accumulated in the glyceride fraction by the following mechanism: The PUFA-partial glycerides generated by the hydrolysis were converted to PUFA-triglycerides by condensation and transacylation reactions. As the PUFA-triglycerides formed were the poor substrates of lipase, they were accumulated in the reaction mixture.