Upgrading of Farmed Salmon Oil Through Lipase-Catalyzed Hydrolysis

Upgrading of farmed salmon oil obtained from by-products was carried out by lipase-catalyzed hydrolysis to increase omega 3 polyunsaturated fatty acids (PUFA) content. The lipases tested were from Penicillium camembertii (PC), Rhizomucor javanicus (RJ), Rhizopus niveus (RN), Rhizopus delemar (RD), Burkholderia cepacia (BC), Rhizopus oryzae (RO), Candida rugosa (CR) and Rhizomucor miehei (RM). The lipases from PC, RJ and RN had lower hydrolysis degrees (HDs) compared to the rest of the lipases. The lipase from CR had the highest HD after 24 h (91.89%). Moreover, CR lipase was the most effective one in concentrating omega 3 PUFA. The final value was increased from 13.77% to 27.81% (wt%). The changes in omega 3 PUFA content were significantly different among the lipases although the HD values were similar at the end of the reactions, which was believed to be caused by the substrate specificities of the lipases. The investigation of the relationship between HD and hydrolysis resistant value (HRV) for eicosapentaenoic acid (EPA, 20:5), docosahexaenoic acid (DHA, 22:6) and oleic acid (OA, 18:1) revealed that the fatty acid (FA) selectivity of the lipases were significantly different. CR lipase had the highest preference for hydrolyzing OA selectively over EPA and DHA. The reaction conditions, i.e. presence of surfactants, sonication, buffer-to-oil ratio, enzyme load, did not affect the selectivity. Investigation of the reaction conditions revealed that it was possible to obtain ~2.15-fold of the original omega 3 PUFA content by hydrolysis of salmon oil in the presence of CR lipase (4%, based on oil weight) with a bufferto-oil ratio of 2:1 (v/v) at 37 o C for 4 h.