Enzymatic fractionation and enrichment of n−9 PUFA

Abstract

AbstractA single‐cell oil from a Mortierella alpina mutant (TGM17 oil) contains n−9 PUFA: 14.3 wt% 6,9‐octadecadienoic acid (18∶2n−9; n−9 LnA) and 17.1 wt% Mead acid (20∶3n−9; MA). Lipase screening indicated that Pseudomonas aeruginosa lipase acted strongly on n−9 LnA and weakly on MA, and Candida rugosa lipase acted weakly on the two PUFA. Hence, fractionation and enrichment of the two FA were conducted with the lipases. The first step was selective hydrolysis of IGM17 oil with P. aeruginosa lipase. The hydrolysis fractionated the oil into FFA containing 20.4 wt% n−9 LnA and 6.3 wt% MA, and acylglycerols containing 10.7 wt% n−9 LnA and 23.7 wt% MA. The FFA fraction was used for preparation of n−9 LnA‐rich FFA. After removal of saturated FA, the FFA were esterified with lauryl alcohol (LauOH) using C. rugosa lipase. Two selective esterifications increased the n−9 LnA content to 54.0 wt% with 38.2% recovery of the initial content of TGM17 oil. The acylglycerol fraction obtained in the hydrolysis with P. aeruginosa lipase was used for preparation of MA‐rich FFA. The acylglycerol fraction was hydrolyzed under alkaline conditions, and saturated FA were eliminated by urea adduct fractionation. Two selective esterifications of the FFA with LauOH increased the MA content to 60.2 wt% with 53.5% recovery. Thus, the two‐step enzymatic process was effective for fractionation and enrichment of n−9 LnA and MA.