Kinetic and mechanistic investigation of microwave-assisted lipase catalyzed synthesis of citronellyl acetate

Abstract

Citronellyl acetate (also known as citronellol acetate) is an important perfumery chemical which can be produced both by chemical catalysis and by biocatalysis. In the current work, Novozym 435 (Candida antarctica lipase B immobilized on polyacrylic resin) was employed to synthesize citronellol acetate directly from citronellol and vinyl acetate under the influence of microwave irradiation vis-à-vis conventional heating. The effects of various parameters affecting the conversion and initial rates of transesterification were studied to deduce the kinetics and mechanism. The enzyme inhibition was studied in conjunction with both modes of heating. Under microwave irradiation, there was an increase in lipase activity due to enhanced collision of molecules, which can in turn be attributed to an increase in the entropy of the system. The synergistic effect of reaction media and microwaves on lipase activity was analyzed. The enzyme is inhibited by alcohol, which is reduced significantly by microwaves. The analysis of the initial rate data and progress curve data showed that the reaction obeys the ping-pong bi−bi mechanism with inhibition by citronellol and vinyl acetate. The experimental and theoretical values match very well.