Concentration of eicosapentaenoic acid by selective esterification using lipases

The aim of this work was to increase the content of EPA in FFA extracts from a commercial oil (43.1% EPA) and from Phaeodactylum tricornutum oil, a single-cell oil, by selective enzymatic esterification. Initially, the FFA extract was esterified with lauryl alcohol using nine lipases. All the lipases concentrated EPA in the unesterified FFA fraction. The criterion used to choose the best lipase was maximization of the dimensionless effectiveness factor (F_AE). This factor grouped the concentration factor (ratio between the EPA concentrations in the FFA fractions before and after esterification) with EPA recovery in the final FFA fraction. Experiments were carried out to correlate F_AE and the degree of esterification (ED, percentage of initial FA converted to lauryl esters). Lipase AK from Pseudomonas fluorescens was the most effective for concentrating EPA. Studies, of the optimal temperature, substrate molar ratio, solvent/substrate ratio, and treatment intensity (product of the lipase mass and the reaction time) were also carried out using the lipase. The maximum F_AE was obtained when the ED was 60%: EPA concentration was 72%, and recovery was 73%. Finally, this lipase was used to concentrate EPA from a FFA extract from P. tricornutum (23% EPA). The content of EPA in the unesterified FFA fraction increased to 71% at 78% ED (recovery of EPA, 75.5%). Comparison of the results of obtained with the two FFA extracts seemed to indicate that the selectivity of Lipase AK for EPA depended on the content of EPA, with higher contents of EPA in the initial FFA mixture reducing the selectivity for EPA.