Abstract
A method has been developed to immobilize lipase from Candida rugosa on modified natural wool fibers by means of graft copolymerization of poly ethylacrylate in presence of potassium persulphate and Mohr's salt redox initiator. The activities of free and immobilized lipase have been studied. FTIR spectroscopy, scanning electron microscopy, and the Bradford method were used to characterize lipase immobilization. The efficiency of the immobilization was evaluated by examining the relative enzymatic activity of free enzyme before and after the immobilization of lipase. The results showed that the optimum temperature of immobilized lipase was 40 degrees C, which was identical to that of the free enzyme, and the immobilized lipase exhibited a higher relative activity than that of free lipase over 40 degrees C. The optimal pH for immobilized lipase was 8.0, which was higher than that of the free lipase (pH 7.5), and the immobilization resulted in stabilization of enzyme over a broader pH range. The kinetic constant value (km) of immobilized lipase was higher than that of the free lipase. However, the thermal and operational stabilities of immobilized lipase have been improved greatly. (C) 2009 Elsevier Ltd. All rights reserved.