Regioselective incorporation of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) into phosphatidylcholine (PC) was carried out using enzymatic and chemical synthesis. Incorporation at the sn-1 position was successfully achieved by lipase-catalysed esterification of 2-palmitoyl-lysophosphatidylcholine (LPC), although in most cases, the enzymes incorporated EPA and DHA at lower rates than other fatty acids. For the incorporation of DHA, Candida antarctica lipase B was the only useful enzyme, while incorporation of EPA was efficiently carried out using either this enzyme or Rhizopus arrhizus lipase. The highest yields in the lipase-catalysed reactions were obtained at the lowest water activity (close to 0). However, by carrying out the reactions at a higher water activity of 0.22, more EPA and DHA were incorporated. Esterification of 2-palmitoyl-LPC with pure EPA at this water activity converted 66 mol-% of LPC to PC using Rhizopus arrhizus lipase as catalyst. When the fatty acid was DHA and the catalyst Candida antarctica lipase B, 45 mol-% of PC was obtained. For incorporation of EPA and DHA at the sn-2 position, phospholipase A(2) was used, but the reaction was very slow. Chemical coupling of 1 -palmitoyl-LPC and EPA or DHA was more efficient, resulting in complete conversion of LPC.
- Industriell bioteknik