Separation of saturated fatty acids from docosahexaenoic acid-rich algal oil by enzymatic ethanolysis in tandem with molecular distillation.

Abstract

Algal oil, rich in docosahexaenoic acid (DHA) and an environmentally sustainable source of ω‐3 fatty acids, is receiving increasing attention. In the present study, a novel approach combining ethanolysis with a 1,3‐specific immobilized lipase (Lipozyme® TL IM) and molecular distillation was investigated to increase the DHA content of algal oil. Algal oil with a 45.94% DHA content was mixed with ethanol, pumped into a column filled with Lipozyme® TL IM, and then circulated for 4 hr at room temperature. The ethanol was then recycled by vacuum distillation. At an evaporator temperature of 150°C, the residue was separated by molecular distillation into a heavy component enriched with DHA glycerides (in the form of triglyceride (TG), diglyceride (DG), and monoglyceride (MG)) and a light component enriched with palmitic acid (PA) and DHA ethyl ester (EE). As a result, 76.55% of the DHA from the algal oil was present in the heavy component, whose DHA content was 70.27%. DHA‐MG was collected in the heavy component mostly in the form of 1‐MG. Lipozyme® TL IM appeared to specifically target PA rather than DHA at the sn‐1(3) position. The Lipozyme® TL IM allowed 90.03% of the initial DHA yield to be retained after seven reaction cycles. Therefore, an eco‐friendly and simple method for increasing the DHA content in algal oil has been developed.