Preparation of Cu(II) adsorbed chitosan beads for catalase immobilization

Abstract

Glutaraldehyde pretreated crosslinked chitosan beads (Ch) were used for Cu(II) adsorption (Cu-Ch). The amount of adsorbed copper was determined using atomic absorption spectroscopy. Adsorption of the copper onto the chitosan was studied batch adsorption technique at 20 °C. In adsorption experiments a Langmiur type (L) adsorption was found with respect to the Giles classification system. Binding parameters such as initial binding constant ( Ki), equilibrium constant ( K), monolayer covarege ( n), site-size ( u), maximum fractional occupancy ( θ) and free energy of adsorption (Δ G) for the chitosan/copper system were calculated Langmiur linearization method. Glutaraldehyde pretreated crosslinked chitosan beads (with and without copper) were used in catalase (CAT) immobilization. Various characteristics of immobilized catalase such as, the temperature activity curve, thermal stability, operational stability, and storage stability were evaluated. Among them optimum temperature were found to be 25–35 °C and 35 °C for Cu-Ch-CAT, Ch-CAT, respectively. The apparent Km value was 18 mM whereas the Vmax was calculated as 4800 μmol (mg protein min) −1 for immobilized catalase on chitosan beads (Ch-CAT) at 35 °C. The apparent Km value was 53 mM and the Vmax value was 18450 μmol (mg protein min) −1 for immobilized catalase on Cu(II) adsorbed chitosan beads (Cu-Ch-CAT) at 35 °C. Operational, thermal and storage stabilities of the Cu-Ch-CAT were higher than that of Ch-CAT. This study demonstrated that the potential of cross-linked chitosan beads applied to metal sorption and enzyme immobilization.