Immobilization of horseradish peroxidase into cubic mesoporous silicate, SBA-16 with high activity and enhanced stability.

Mesoporous silicate, SBA-16 is one of the most promising supports for horseradish peroxidase. In this study, SBA-16 was synthesized, and the anchored HRP enzyme in the organized porous networks, SBA-16. The mesoporous material, SBA-16 and the anchored HRP enzyme were characterized by Fourier transform infrared, scanning electron microscopy, transmission electron microscopy, N2 adsorption-desorption isotherms, low-angle XRD and thermogravimetric analysis. The percentage of immobilized HRP was 57%. The enzyme affinity constant, Km values of soluble and immobilized enzyme were 5.27 and 3.9 mM for hydrogen peroxide and 12 and 10.4 mM for guiacol, respectively, indicating that the immobilized enzyme had more affinity to the substrate than free HRP. Also, the free and immobilized enzyme had pH and temperature optima at 5.6, and 40 °C, respectively. The free enzyme was stable at 40 °C but that for the immobilized enzyme was detected up to 60 °C. Reusability of immobilized enzyme was found to be 10 cycles; the immobilized enzyme can only retain 50% of its activity after 5 cycles. The results indicate the higher efficiency, stability, and reusability of the immobilized enzyme than free enzyme. The HRP immobilized to SBA-16 due to the large surface area, and narrow pore size distribution of SBA-16.