Desenvolvimento de membranas de polissulfona para imobilização de lipase

Abstract

Preparation and characterization of polysulfone (PSU) membranes and the immobilization of lipase enzyme in these membranes to produce enantioselective membranes, in order to separate chiral compounds, is the subject of the present work. PSU membranes were prepared by phase inversion, using chloroform as solvent and water as nonsolvent. Membranes with different thickness were prepared and phase inversion parameters such as (solution concentrations, solvent evaporation time, drying and thermal treatment) were investigated. Membranes were characterized, in order to use them in electrodialysis process (ED) and in the lipase PS enzyme immobilization. For immobilization, bifunctional agent glutaraldehyde was used to link the enzyme to the polymer. On immobilization, the kinetic constants (Km e Vmax), the amount of immobilized enzyme with Bradford method and the activity of free and immobilized enzyme with p-nitrophenyl acetate (PNPA) hydrolysis, were determined. PSU membranes prepared by phase inversion are hydrophobic and, when compared with Selemion®; CMT and CMV commercial membranes, present lower permeselectivity, lower ion exchange capability and higher resistance. Membranes pore diameter is lower than 100 nm. The maximum amount of immobilized enzyme in the membranes reached 2.35 mg per gram of polymer after 18 hours of immobilization with a 61,2% yield . Enzyme activity decays after immobilization , from 14780 U.g-1 (free enzyme) to 1184 U.g-1 (immobilized enzyme).