Miniemulsion as efficient system for enzymatic synthesis of acid alkyl esters

The aim of this work is to devise an efficient enzymatic process for the production of linear alkyl esters in aqueous miniemulsion systems. The esterification reactions of linear alcohols and carboxylic acids were performed with three different enzymes, commercial Amano lipase PS from Pseudomonas cepacia, Lipase type VII from Candida rugosa, and lyophilized Fusarium solani pisi cutinase expressed in Saccharomyces cerevisiae SU50. The miniemulsion system shows a high potential for the synthesis of linear alkyl esters, for example, hexyl octanoate, which could be synthesized with an ester yield of 94% using Amano lipase PS. Even with hydrophilic alcohols as ethanol, ethyl decanoate could be obtained with a concentration of 0.45 M and a yield of 62% using F. s. pisi cutinase as catalyst. High esterification rates for ethyl- and hexyloleate in miniemulsion showed a significant shift in cutinase selectivity towards longer chain length carboxylic acids. The stepwise addition of the alcohol led to an increase of the esterification yield. Moreover, increasing the amount of dispersed organic phase, mainly consisting of the substrates, led to a significant increase of the final ester concentration (e.g., concentration of 1.4 M for ethyl decanoate for the esterification with Amano Lipase PS).