Kinetics and mechanism of lipase catalyzed monoacylglycerols synthesis

Monoacylglycerols are increasingly used in several industrial applications as effective and cheap emulsifiers. In the present work monostearin synthesis has been studied, using lipase as a biocatalyst of the esterification reaction of stearic acid with (R,S)-1,2-O-iso-propylidene glycerol (solketal). The lipase from Candida antarctica (CaL B) was immobilized in AOT/isooctane water in oil microemulsions. Optimization of the reaction conditions have shown that the highest production (80% in 30 min) could be achieved at 40 degrees C, in microemulsions with relatively low water content (w(o) = 8). Kinetic studies have shown that the esterification reaction of stearic acid with solketal catalyzed by CaL B occurs via the ordered bi-bi mechanism, in which inhibition by the acid was identified. Moreover, at high fixed solketal concentrations a negative cooperativity is pronounced, which means that binding of the alcohol lowers the affinity of the enzyme for binding of the acid. Values of all kinetic parameters have been determined. (C) 2013 Elsevier B.V. All rights reserved.