Concentration of docosahexaenoic acid by enzymatic alcoholysis with different acyl-acceptors, using tert-butanol as reaction medium

Abstract

The aim of this work was to produce docosahexaenoic acid (DHA)-enriched acylglycerols through the alcoholysis of tuna oil (24-26% DHA) using ethanol, dodecanol and isobutanol as the acyl-acceptors. The alcoholysis reaction was catalyzed using Thermomyces lanuginosus lipase (Lipozyme TL IM) and was carried out both in solvent-free medium and using tert-butanol to increase lipase stability. Studies were carried out to determine the influence of the reaction time and the lipase/oil ratio. The tuna oil’s DHA content was trebled (from 26 to 78 wt%) using isobutanol as the acyl acceptor while carrying out the alcoholysis reactions in solvent-free medium. However, under these conditions, the lipase was partially deactivated given that the conversion rate decreased by around 80% after catalyzing six successive reactions using the same lipase batch. With tert-butanol as the reaction medium, the lipase was more stable but the resulting DHA concentrations were lower: 56% with isobutanol and dodecanol (59% with dodecanol in solvent-free medium) and 42.5% with ethanol (47.5 % without solvent).