Immobilization of lipase by filtration into a specially designed microstructure in the CA/PTFE composite membrane

Abstract

A specially designed microstructure in the composite membrane with a porous hydrophobic layer and a relatively dense hydrophilic layer is proposed for lipase immobilization. Firstly, the composite membrane was prepared by coating the cellulose acetate layer with the average pore size of 1.40 nm on the hydrophobic PTFE layer with the average pore size of 76.3 nm. Then, enzymes were absorbed in pores of PTFE layer and deposited on the interface between the two layers by the filtration process. The relatively dense CA layer was used to reject the enzymes controlling the enzyme loading which prevented enzymes from being dissolved into the aqueous phase. The porous PTFE layer supplied a hydrophobic environment and a large specific surface area for the immobilization of lipases which were propitious to the activation of lipase. The activity of immobilized lipase membrane based on hydrolysis of olive oil was assayed in the biphasic membrane reactor and the maximum specific activity (1.20 ± 0.04 μmol-FFA min −1 cm −2) was found to be higher than the value reported in some literature. The kinetic parameters of the immobilized lipases, K m and k max were fitted with the Michaelis–Menten equation. The Thiele modulus ( φ) was used to evaluate the effect of the mass transfer through the membrane on the performance of reaction systems. The optimum enzyme loading (0.020 ± 0.002 mg-protein cm −2) was obtained with the highest activity and without the diffusion-limited. Furthermore, the immobilized lipases retained 80% residual activity after ten hydrolysis cycles. The composite membrane was easily regenerated and lipases immobilized in the regenerated membrane remained a high activity.