Activity of Laccase Immobilized on TiO(2)-Montmorillonite Complexes

The TiO(2)-montmorillonite (TiO(2)-MMT) complex was prepared by blending TiO(2) sol and MMT with certain ratio, and its properties as an enzyme immobilization support were investigated. The pristine MMT and TiO(2)-MMT calcined at 800 °C (TiO(2)-MMT800) were used for comparison to better understand the immobilization mechanism. The structures of the pristine MMT, TiO(2)-MMT, and TiO(2)-MMT800 were examined by HR-TEM, XRD and BET. SEM was employed to study different morphologies before and after laccase immobilization. Activity and kinetic parameters of the immobilized laccase were also determined. It was found that the TiO(2) nanoparticles were successfully introduced into the MMT layer structure, and this intercalation enlarged the “d value” of two adjacent MMT layers and increased the surface area, while the calcination process led to a complete collapse of the MMT layers. SEM results showed that the clays were well coated with adsorbed enzymes. The study of laccase activity revealed that the optimum pH and temperature were pH = 3 and 60 °C, respectively. In addition, the storage stability for the immobilized laccase was satisfactory. The kinetic properties indicated that laccase immobilized on TiO(2)-MMT complexes had a good affinity to the substrate. It has been proved that TiO(2)-MMT complex is a good candidate for enzyme immobilization.