Ag-induced Efficient Immobilization of Papain on Silica Spheres

Complexation and interaction between silver and amino group were applied to induce an efficient immobilization of papain on silica spheres. The silver nanoparticles were deposited on the silica spheres before papain was coupled to the silica spheres. The silica spheres with silver nanoparticles were characterized by high resolution transmission electron microscopy (HR-TEM), Fournier transform infrared spectroscopy (FT-IR), and UV-Vis scanning spectrometer. FT-IR spectrum was also used to characterize the immobilized and free papain. Effect of some factors on the activities of the immobilized papain was investigated. It was observed that the coupled yield and relative activity of the papain on Ag/SiO₂ were 1.17 and 1.86 times of those on the bare SiO₂, respectively. At an optimum concentration of silver, the observed activity of the immobilized papain was 2.1 times of that on the bare silica. In addition, the maximum specific activity of papain immobilized on Ag/SiO₂ was 819.9 U·mg^-1, which is slightly lower than that of the free papain, 906.2 U·mg^-1. Stability of the immobilized papain was also examined. The results indicate that the silver nanoparticles successfully induce a fine immobilization of papain.