Kinetic modelling and kinetic parameters calculation in the lipase-catalysed synthesis of geranyl acetate

Abstract

The interest in new natural products used in cosmetic industry has increased the research in order to synthesize those compounds. The aim of this work is to assess the reaction of the transesterification between geraniol and vinyl acetate for the enzymatic synthesis of geranyl acetate, using Novozym® 435 as catalyst, as well as to obtain a kinetic model for the bioprocess and the values of the kinetic parameters. Five experimental series have been performed with variation of: enzyme amount, concentrations of geraniol and vinyl acetate in molar ratio 1:1, stirring rate, temperature and, finally, substrates molar ratio. A conversion of geranyl acetate of 98.4% has been obtained in the best experimental conditions and, also, high conversions were obtained for most of the other conditions assayed. It has been concluded that the catalyst amount is the most significant variable on the reaction kinetics and the reaction yield and that both the stirring rate and the initial substrates concentrations have no significant influence. Finally, a Ping–Pong bisubstrate kinetic model has been applied and its kinetic parameters have been determined by using an improved version of a procedure developed by authors in a previous work. The values obtained for the Michaelis constants show that, for the equal substrates concentrations series, the Ping–Pong model can be simplified to a pseudo-first order kinetic model, which has been confirmed, with high correlation coefficients, by using the “Curve Expert” software.