Enrichment of DHA from tuna oil in a packed bed reactor via lipase-catalyzed esterification

A packed-bed reactor (length 6.5 cm; id 4.65 mm) has been used to enrich docosahexaenoic acid (DHA) via the lipase-catalyzed esterification of the fatty acid from tuna oil with ethanol. Lipozyme RM IM (from Rhizomucor miehei) was used for the esterification reaction because of its ability to discriminate between different fatty acids, and several reaction parameters, including the temperature, molar ratio of substrates, and water content were explored as a function of residence time. In this way, the optimum conditions for the enrichment process were determined to be a temperature of 20 °C, a molar ratio of 1:5 (i.e., fatty acid to ethanol), and a water content of 1.0 % (based on the total substrate weight). Under these conditions, a residence time of 90 min gave a DHA concentration of 70 wt% and a DHA recovery yield of 87 wt% in the residual fatty acid fraction.