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

This study focused on developing bentonite–cysteine (Bent–Cys) microcomposite affinity sorbents (38–105 μm) 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 μmol 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.