Comparative Fatty Acid Selectivity of Lipases in Esterification Reactions with Glycerol and Diol Analogues in Organic Media

Reaction selectivity of Pseudomonas cepacia, Rhizomucor miehei, and Candida antarctica B lipases was assessed in multicompetitive esterification reaction mixtures containing an homologous series of n-chain even carbon number fatty acid (FA; C4C18) substrates and a single alcohol cosubstrate (glycerol, 1,2-propanediol (1,2-PD), or 1,3-propanediol (1,3-PD)) in tert-butyl methyl ether at water activity of 0.69 or 0.90 and a reaction temperature of 35 °C. For P. cepacia lipase, the ordinal patterns of FA selectivities observed were, with glycerol, C8 > C10, C6, C16 > other FA; with 1,2-PD and 1,3-PD, C16 > C8 > C14 > other FA. For R miehei lipase, the ordinal patterns of FA selectivities observed were, with glycerol, C8 > C12 > C10, C14 > other FA; with 1,2-PD and 1,3-PD, C8 > C12 > other FA. For C. antarctica B lipase, the ordinal patterns of FA selectivities observed were, with glycerol, C8 > C10, C6, C12 > other FA; with 1,2-PD, C8 > C10, C6 > other FA; and with 1,3-PD, C8 > C10 > C6 > other FA. The differences in selectivity among FA ranged up to 16-fold, depending upon the lipase and alcohol cosubstrate used. These findings represent intrinsic and substratemodulated features of FA selectivities that are of particular relevance to the use of lipases for acylglycerol synthesis reactions.