Reversible immobilization of catalase by using a novel bentonite-cysteine (Bent-Cys) microcomposite affinity sorbents

Abstract

This study focused on developing bentonite-cysteine (Bent-Cys) microcomposite affinity sorbents (38-105 ?m) for catalase adsorption from aqueous solutions. Pseudo-biospecific affinity ligand l-cysteine was covalently binded onto the bentonite structures. X-ray diffraction and FTIR analysis of Bent-Cys composite affinity sorbents were performed. According to X-Ray diffraction data, cysteine molecule is parallel to the tetrahedral-octahedral-tetrahedral layer (TOT silicate layer) and is a monolayer in the inner layer space of the structure. The surface areas of the Bentonite and Bent-Cys microcomposite structures were found as 33.00 ± 0.30 and 22.80 ± 0.30, respectively. An elemental analysis of immobilized l-cysteine for nitrogen was estimated to be 541.3 ?mol g-1 bentonite. Catalase adsorption onto the microcomposite affinity sorbents from aqueous solutions containing different amounts of catalase at different pH was investigated in a batch system. The maximum catalase adsorption capacity of the Bent-Cys microcomposite affinity sorbents was 175 mg g-1. The non-specific catalase adsorption onto the bentonite was very low (about 2.7 mg g-1). The activity yield decreased with the increase of the enzyme loading. It was observed that there was a significant change between Vmax value of the free catalase and Vmax value of the adsorbed catalase on the Bent-Cys microcomposite affinity sorbents. The Km value of the immobilized enzyme was higher 1.1 times than that of the free enzyme. Optimum operational temperature was 10 °C higher than that of the free enzyme and was significantly broader. It was observed that enzyme could be repeatedly adsorbed and desorbed without loss of adsorption capacity or enzyme activity. © 2008 Elsevier B.V. All rights reserved.