Lipase immobilization onto polyethylenimine coated magnetic nanoparticles assisted by divalent metal chelated ions

Abstract

In this study, polyethylenimine coated Fe3O4 magnetic nanoparticles (Fe@PEI) were prepared and used for three metal ions (Co2+, Cu2+ and Pd2+) chelation. The metal chelated magnetic nanoparticles (Fe@PEI-M) were characterized by using different spectroscopic and analytical techniques. The metal contents were analyzed by inductively coupled plasma atomic emission spectroscopy (ICP) and energy-dispersive X-ray spectroscopy (EDX). Thermomyces lanuginosa lipase (TLL) was then immobilized onto the modified magnetic supports by physical adsorption. Fe@PEI-Co and Fe@PEI-Cu showed better activity at extreme temperature and pH values than of the free enzyme. After 10 cycles of successful biocatalytic activity performed by immobilized lipase on Fe@PEI-Co, more than 60% of initial activity was reserved. Furthermore, the immobilized lipase onto Fe@PEI-Co retained about 80% of its initial activity after 14 days of storage. The immobilized lipase on the selected nanocomposite was then used for synthesis of ethyl valerate. After 24h incubation time, the extent of esterification was found to be 70 and 60% in n-hexane and DMSO media, respectively.