Esterification reactions catalysed by surfactant-coated Rhizopus arrhizus lipase

Abstract

The esterification activity of microbial lipase (triacyl glycerol hydrolase, E.C. 3.1.1.3) in water-organic biphasic solvent system has been investigated. The lipase produced from Rhizopus arrhizus NCM997 strain by solid-state fermentation, using rice bran as substrate, exhibited novel capability of catalyzing esterification reaction. The partially purified lipase was coated with nonionic surfactant (Span 60). The esterification activity of the enzyme was found to be optimum at 30°C and pH 6.5, and isooctane was the best solvent for esterification. Surfactant-coated lipase showed enhanced esterification activity compared to native enzyme. Among the substrates tested, palmitic acid and glycerol gave maximum conversion of 74.02%. Effect of initial water activity has been investigated using different salts of varying water activity. The maximum conversion (85.75%) of ester was obtained with salts having less water activity (LiCl; aw. 0.12). Thus, this surfactant-coated microbial lipase in organic solvent (isooctane) has a good potential of biocatalysis.