Incorporation of docosahexaenoic acid (DHA) into evening primrose (Oenothera biennis L.) oil via lipase-catalyzed transesterification

Six commercial lipases (Novozym 435 from Candida antarctica, Lipozyme IM from Mucor miehei, PS-30 from Pseudomonas sp., AP-12 from Aspergillus niger, AY-30 from Candida rugosa, and Novozym-677BG from Thermomyces lanuginosus) were tested for their ability to incorporate docosahexaenoic acid (DHA; 22:6ω3) into evening primrose oil. Among the enzymes examined, Novozym 435 from Candida antarctica was chosen over the other enzymes to catalyse the transesterification reaction owing to higher incorporation of DHA. As enzyme concentration, substrate mole ratio and incubation time increased, incorporation of DHA also increased. For the time course reaction, incorporation of DHA increased up to 25.2% after 24 h. The highest DHA incorporation (37.4%) occurred at a substrate mole ratio of 1:3 (evening primrose oil: DHA). The positional distribution of the various fatty acids, between the sn-1,3 and sn-2 positions on the glycerol backbone, was also determined. Evening primrose oil containing DHA was successfully produced and may be useful in certain food and nutraceutical applications.