Synthesis of wax ester through triolein alcoholysis: Choice of the lipase and study of the mechanism

Eight microbial lipases and one animal tissue lipase were tested for their ability to support alcoholysis between triolein and stearyl alcohol to produce wax ester. The lipases from Alcaligenes sp. and Chromobacterium viscosum were shown to produce the best ester yield (about 53%); however, the reaction was catalyzed in a shorter length of time using the lipase from Alcaligenes sp. (5 h) as compared to the lipase from C. viscosum (200 h). The lipases from Mucor javanicus, Mucor miehei, and Pseudomonas fluorescens showed 35% ester yield within 150 h. The other lipases, i.e., the lipases extracted from porcine pancreas, Candida rugosa, Rhizopus javanicus, and Rhizopus niveus showed only low catalytic activity (less than 20%). The lipase from Alcaligenes sp. was used for further investigations on the mechanism of the reaction. A regioselectivity toward the sn-1,3-positions of the acylglycerols was shown during the first hours of reaction. After 5 h when ester synthesis and triolein consumption stopped, the continuous evolution of the concentration of monoolein and diolein isomer forms was ascribed to isomerization reactions.