Kinetics of the enzymatic hydrolysis of triglycerides in o/w emulsions: Study of the initial rates and the reaction time course

Abstract

The hydrolysis of emulsified tributyrin by Thermomyces lanuginosus lipase (TLL) has been studied by titrimetric and colorimetric measurements as well as by thin-layer chromatography (TLC). A kinetic model have been developed and applied to the initial reaction rates as well as to simulate the time course of the hydrolysis reaction at several temperatures, lipase concentrations and volume fractions of tributyrin. The model successfully predicted the initial reaction rates, even at saturating enzyme concentrations, with a relative deviation of less than 5%. The reaction-progress curves predicted by the model also agree with the experimental results significantly. The combined analysis both of the experimental results and of the simulations suggests that the hydrolysis of tributyrin by TLL proceeds through two separate stages which partially overlap. In the first one, the main reaction is the hydrolysis of one of the outer ester groups (sn-1 or 3) of the tributyrin molecule. The second stage starts when the interface becomes saturated of diglyceride, and involves mainly the hydrolysis of the remaining outer ester bond. The results found offer valuable information on the time course of the enzymatic hydrolysis of emulsified triglycerides, which is useful for some of the applications of these enzymes, such as free fatty acid production, wastewater treatment or washing processes.