Enrichment of docosahexaenoic acid from tuna oil via lipase-mediated esterification under pressurized carbon dioxide

• The pressurized CO2 was effective reaction medium for the enrichment of DHA via esterification of tuna oil fatty acid and ethanol.
• DHA was enriched in residual fatty acid by discriminative characteristic of Lipozyme RM IM against DHA.
• The pressurized CO2 prepared at 25 °C, and 8.3 MPa was the most effective.
• DHA concentration and recovery yield at an optimum condition were 75.8% and 81%, respectively.

This study focused on the use of pressurized CO2 as a reaction medium for the enrichment of docosahexaenoic acid (DHA) from tuna oil fatty acids via lipase-mediated esterification. Of the three lipases tested, Lipozyme RM IM from Rhizomucor miehei was selected for further study. Enzyme loading, water addition, and reaction time were also explored. Near-supercritical CO2, prepared at 25 °C and 8.3 MPa, was the most effective reagent tested for enriching DHA from the residual fatty acid fraction. In addition to near-supercritical CO2, optimal conditions included addition of 0.2 wt% (based on total substrates) water, enzyme loading of 5 wt% (based on total substrates), and a reaction time of 18 h. The DHA concentration and recovery yield for the residual fatty acid fraction under these optimal conditions were 75.8 wt% and 81 wt%, respectively.

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