Modification of Stearidonic Acid Soybean Oil by Immobilized Rhizomucor miehei Lipase to Incorporate Caprylic Acid

Abstract Immobilized sn‐1,3 specific Rhizomucor miehei lipase (RML) was used to catalyze the incorporation of caprylic acid (C8:0) into high stearidonic acid (SDA, C18:4ω3) soybean oil (SDASO) to form structured lipids (SL). The effects of type of biocatalyst (Celite‐, octyl‐Sepharose‐, and Duolite‐immobilized RML) and reaction temperature (30, 40, 50, and 60 °C) on acidolysis and acyl migration were studied. Celite‐immobilized RML (C‐RML) at 50 °C maximized C8:0 incorporation and minimized acyl migration compared to other treatments. Optimal levels of substrate molar ratio (C8:0 to SDASO), incubation time, and enzyme load for SL synthesis by C‐RML at 50 °C was determined by response surface methodology to be 6:1, 24 h, and 20 % weight of substrates, respectively. This optimum treatment was scaled‐up in hexane or solvent‐free reaction media using SDASO or an SDA‐enriched acylglycerol mixture as substrate. This yielded various SL with C8:0 contents ranging from 17.0 to 32.5 mol% and SDA contents ranging from 20.6 to 42.3 mol%. When digested, these SL may deliver C8:0 for quick energy and SDA for heart health making them potentially valuable for medical and nutraceutical applications.