Invertase immobilization onto radiation-induced graft copolymerized polyethylene pellets

The graft copolymer poly(ethylene-g-acrylic acid) (LDPE-g-AA) was prepared by radiation-induced graft copolymerization of acrylic acid onto low density polyethylene (LDPE) pellets, and characterized by infrared photoacoustic spectroscopy and scanning electron microscopy (SEM). The presence of the grafted poly(acrylic acid) (PAA) was established. Invertase was immobilized onto the graft polymer and the thermodynamic parameters of the soluble and immobilized enzyme were determined. The Michaelis constant, K-m, and the maximum reaction velocity, V-max, were determined for the free and the immobilized invertase. The Michaelis constant, K-m was larger for the immobilized invertase than for the free enzyme, whereas V-max was smaller for the immobilized invertase. The thermal stability of the immobilized invertase was higher than that of the free enzyme. Copyright (C) 1996 Elsevier Science Ltd.