HYDROLYSIS AND REGIOSELECTIVE TRANSESTERIFICATION CATALYZED BY IMMOBILIZED LIPASES IN MEMBRANE BIOREACTORS

An experimental study of two types of immobilized lipase membrane reac tors for the bioconversion of lipophilic substrates is reported. In on e part of the work, the performance of biphasic membrane reactors has been investigated as a function of selected operating conditions for t he hydrolysis of olive oil. In this type of reactor, aqueous and organ ic phases flow tangentially past the two surfaces of an enzyme contain ing membrane; intramembrane mass transfer is diffusive. Another part o f the study refers to the regioselective transesterification of 5,7-di acetoxyflavone in a monophasic non-aqueous membrane reactor wherein an organic phase solution of substrate is crossflow filtered through the wall of a tubular enzyme-loaded membrane; in this case, intramembrane mass transfer is convective. Immobilization of the enzyme both within the interior of the membranes and at their surfaces is considered. Th e influence of fluid dynamics parameters and immobilization site on th e biphasic reactors performance has been studied using lipase from Can dida rugosa. The effect of immobilization, of the amount of immobilize d enzyme on the catalytic activity and regioselectivity efficiency in non aqueous system have been investigated using lipase from Pseudomona s cepacea. The observed specific activity of the enzyme in the biphasi c membrane system was higher at relatively high transmembrane pressure , high aqueous flow rate and low organic phase flow rate. Immobilizati on of the enzyme in the sponge layer of the asymmetric membrane allowe d higher catalytic activity and stability with respect to the enzyme i mmobilized on the dense layer. The stability and specific activity of the lipase Immobilized in the monophasic non-aqueous membrane reactor was higher compared to the suspended free lipase and was improved with decreasing the enzyme concentration in the membrane. An high regiosel ectivity for the immobilized lipase was obtained producing an intermed iate natural flavone not yet available.