A predictive kinetic study of lipase-catalyzed ethanolysis reactions for the optimal reutilization of the biocatalyst

Abstract

A new application of the kinetics modeling for the optimal reutilization of an immobilized lipase from Pseudomonas cepacia in the ethanolysis of vegetable oils is presented. Two different rate expressions were explored to take into account the lipase inactivation. The methodology developed is based on the utilization of the pseudo reaction time that indicates how much longer the reaction mixture must remain in the reactor (actual reaction time) to achieve the conversion that would have been achieved if the enzyme had not been partially deactivated (pseudo reaction time). An initial batch of lipase was employed in 15 consecutive trials in order to quantitatively characterize the process over a range of lipase activity and to validate the ability of the methodology utilized to describe the kinetics of both ethanolysis and deactivation. Then, the model developed was employed to predict the time necessary to attain a desired conversion in subsequent reaction cycles in both, trials with the same batch of lipase with different degree of inactivation, and trials with a new batch of immobilized lipase with different specific activity. The reaction times predicted to attain a 38% disappearance of glyceryl ester bonds were experimentally verified by carrying out the corresponding ethanolysis reactions of 100 g of sunflower oil. The agreement between the desired and experimentally attained conversions achieved validates the methodology developed to estimate reaction time in lipase-catalyzed ethanolysis reactions.