Catalytic potential of a nitrocellulose membrane‐immobilized lipase in aqueous and organic media

Artificial membranes are ideal supports for enzyme immobilization and biocatalysis. The binding of a commercial lipase, Lipolase T20 on to nitrocellulose (NC) membrane was achieved by physical adsorption followed by cross‐linking with formalin (2%). The NC‐immobilized lipase was characterized for its catalytic activity and operational stability, using p ‐nitrophenyl palmitate ( p ‐NPP) hydrolysis as a model reaction system. Functionally membrane bound lipase was more stable than free lipase (55°C) at higher temperature (65 and 75°C) and at pH 9.0 to 9.5. The hydrolytic properties of NC‐bound lipase were studied consecutively as a function of physicochemical parameters. The NC‐bound lipase was highly hydrolytic toward relatively longer C‐chain length esters. This indicated a preferential selectivity of NC‐bound lipase toward the p ‐NPP with an activity of 6.03 + 0.30 IU/cm 2 . The nonionic detergents like Tween‐20, 40, and 60 promoted the hydrolytic activity of membrane‐bound lipase, while Tween‐80 prompted a decline in the activity of NC‐membrane bound lipase. Among various salt ions, Ca 2+ , Al 3+ , Zn 2+ , and Cu 2+ showed a stimulatory effect while Fe 2+ , NH 4+ , Cd 2+ , and Zn 2+ antagonized the hydrolytic activity of the bound lipase. The immobilized lipase was studied for its reusability and was found to retain >50% of hydrolytic activity after fifth repetitive cycle. In DMSO, the synthesis of octyl ferulate at 55°C under shaking (150 rpm) using ferulic acid (75 m M ) and 1‐octanol (100 m M ) was achieved with a yield of ˜61 m M of ester (1‐octyl ferulate) as analyzed by gas liquid chromatography. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012