Lipase-catalyzed transesterification in organic solvent : effects of water and solvent, thermal stability and some applications

Abstract The lipase-catalyzed transesterification of tributyrin with various alcohols in a heterogeneous system was investigated using powdered enzyme suspended in numerous organic solvents. There is an optimum water content, (H 2 O) op , where the enzyme shows the maximal activity and its value is affected by the hydration of the enzyme and the substrate, coagulation of the enzyme, the nature (water-miscible/immiscible) of the solvent and the water equilibrium between the enzyme and the substrate solution. In a water-restricted environment, Pseudomonas lipases were very stable and showed enzymatic activities, parts of which were restored by water supplementation. This suggests that a thermally azeotropic dehydration plays a part in the thermoinactivation of the enzyme in organic solvents. The catalytic activity of the enzyme was predominantly determined by the polarity and the structure of the solvent, and the dehydration of the enzyme by the solvent. The reactivity of an aliphatic primary alcohol bearing a straight chain was dependent on the nature of the solvent and differed from that for enzymatic hydrolysis of the corresponding alkyl butyrate in aqueous solution. Investigations of the transesterification with 2-alkanol confirmed a synthetic strategy of the optically active esters and optical resolution of the alcohol.