Use of microemulsion systems as media for heterogeneous enzymic catalysis

Abstract

Lipases catalyze specifically the cleavage of triglycerides to free fatty acids and glycerol. Depending on the reaction media, these enzymes can also be used to catalyze the synthesis or the transesterification of some specific triglycerides. Since these reactions are heterogeneous, taking place at interfaces, they can be performed in water-in-oil microemulsion systems under mild conditions. This approach can give information about the interactions between protein molecules and the surfactant membrane separating the oil/water phases. These interactions can have dramatic influence on the enzymic activity.

The nature of the microemulsion used is crucial, i) in controlling the equilibrium of the reaction from hydrolysis to condensation, depending on the water content; ii) for differences of the solubilization site and catalytic action of the enzyme hosted in the dispersed aqueous phase, the structure of which depends on the surfactant used.

In the present work we studied the catalytic behavior of lipase from Rhizopus delemar in the direction of hydrolysis by using AOT anionic, CTAB cationic, and C₁₂EO₄ nonionic microemulsion systems. Various parameters of the enzymic reaction (such as K _m , pH optimum, T optimum, water content) were studied in these different systems. The results show that in the AOT system the activity of the enzyme is higher in comparison to the other systems.