A catalytic membrane for hydrolysis reaction carried out in the two-liquid phase system - Membrane preparation and characterisation, mathematical model of the process

The paper presents a method of catalytic membrane preparation for the lipase from Candida antarctica. Some methods of enzyme immobilisation as adsorption on surface of different kinds of membrane and chemical binding by glutaraldehyde and by divinylsuffone were tested. It was shown that in the most cases the enzyme after immobilisation presented a high level of catalytic activity and stability. The best results, first of all, thanks to a very high value of the half-life time of enzymatic activity, was obtained after immobilisation by glutaraldehyde on a polyamide membrane. For the preparations formed by this method, the kinetics of hydrolysis of R- and S-glycidyl butyrate was determined in a buffer saturated with isooctane and the constants of Michaelis-Menten equation, such as K-m and r(max), were estimated. For the low substrate concentration the constant (k(r)) of the first-order kinetics was also determined and the values obtained served to develop model validation. The model concerns a two-liquid phase system where the applied membrane serves both as a phase contactor and enzyme carrier. The substrate is transported from one of the phases (usually for hydrophobic reagents it is an organic phase) to the catalysis zone (i.e., to the enzymatic gel layer immobilised on the membrane surface), while the second applied liquid phase (usually water phase) serves as a hydrophilic product receiver. Before the model validation some parameters, such as reactant partition coefficient, diffusion coefficient in the gel layer and mass transfer coefficient in the membrane and continuous phases were determined in separate experiments. A method for calculation of the gel layer thickness, a parameter significant in the process run, was presented. The theoretical results were in good agreement with experiments whose model could be used in the process modelling at the next step of investigations. (c) 2005 Elsevier B.V. All rights reserved.