Lipase catalyzed modification of fish oil to incorporate capric acid

Abstract

Immobilized lipase, IM60, from Rhizomucor miehei, was used as a biocatalyst for the incorporation of capric acid (C10:0) into menhaden fish oil concentrate containing 34.7 mol% eicosapentaenoic acid (20:5n-3) and 34.4 mol% docosahexaenoic acid (22:6n-3). Transesterification (acidolysis) was performed in hexane and solvent-free media. Tocopherol content was analyzed before and after enzymatic modification. Products were analyzed by gas liquid chromatography. After 24 h incubation in hexane, there was an average of 31.1±4.6 mol% incorporation of C10:0 into fish oil, while 20:5 and 22:6 were reduced to 12.6±3.1 and 13.7±4.4, respectively. The solvent-free reaction produced an average of 28.8±4.7 mol% capric acid incorporation; 20:5 and 22:6 decreased to 16.1±5.7 and 13.5±3.0 mol%. The effect of incubation time, substrate mole ratio, enzyme load, and added water were also studied. Generally, as enzyme load, mole ratio, and incubation time increased, mol% capric acid incorporation also increased. Time course of reaction indicated that the highest C10:0 incorporation occurred at 72 h, for both the reaction in hexane (33.5 mol%) and the solvent-free reaction (36.0 mol%). The highest C10:0 incorporation for the substrate mole ratio reaction occurred at a mole ratio of 1:8 in hexane (50.7 mol%) and the solvent-free reaction (36.7 mol%). Although the highest C10:0 incorporation (31.8 and 48.6 mol%) occurred at an enzyme load of 15% in hexane and 20% for the solvent-free reaction respectively, the values were not significantly different (P<0.05) after 5% enzyme load. Mol% incorporation of C10:0 declined with increasing amounts of water. At 1% added water, high C10:0 incorporation was achieved for the reaction in hexane (39.3 mol%) and the solvent-free reaction (26.0 mol%). Pancreatic lipase catalyzed sn-2 positional analysis was performed on the fish oil before and after enzymatic modification. Fish oil containing capric acid was successfully produced and may be beneficial in certain food and nutritional applications.