Covalent immobilization of Candida rugosa lipase on a novel functionalized Fe3O4@SiO2 dip-coated nanocomposite membrane

Abstract

Membrane-immobilized enzymes have received increasing attention in a variety of fields such as biosensors, enzymatic reactors, and membrane bioreactors. In this study, Candida rugosa lipase (CRL) was covalently immobilized on nanocomposite membrane. Initially, the Fe3O4@SiO2 nano-particles were dip-coated onto the ultrafiltration membrane surface through a low temperature hydrothermal (LTH) process, and then, reacted with 3-aminopropyletriethoxysilane (APTS). Glutaraldehyde was used as a coupling agent to covalently immobilize lipase on the nanocomposite membrane surface. Various techniques such as SEM, TEM, XRD, FTIR, AFM, contact angle goniometry and surface free energy measurement were applied to characterize the nanocomposite membrane. The results showed that the immobilization process was successful in terms of enzyme activity and immobilization efficiency. It was found that the activated nanocomposite membrane greatly improved the relative activity and loading capacity in comparison to unmodified UF membrane. The investigation of kinetic parameters of enzymatic reaction shows the decreasing of Km and vmax due to immobilization which represents the increasing of substrate affinity and decreasing of catalytic activity of immobilized enzyme. The higher thermal, storage, and operational stability of immobilized enzyme make it a suitable candidate for to bio-catalytic processes.