Property of papain immobilized on magnetic ferroferric oxide by biosilicification

An approach combining biomimetic mineralization with Fe3O4 magnetic particles (MNPS) was proposed to prepare immobilized papain that was easily separated from reaction mixture. The results from FT-IR spectra showed that aminosilane-modified MNPS was synthesized, and EMNPS was coated with biosilica by biomimetic silicification. When the concentrate of papain was 7.5mg·mL-1, the loading of papain was 0.24mg·mg-1MNPS and the activity of EMNPS and EMNPS/SiO2were 3.72 and 3.66U·mg-1MNPS, respectively. Furthermore, the pH stability, thermal stability and reusability of EMNPS/SiO2were better than EMNPS. Compared with free papain, EMNPS has slightly higher affinity, and EMNPS/SiO2has lower affinity with substrate. The Michaelis constant (Km) for hydrolysis of casein by EMNPS and EMNPS/SiO2were 1.39 and 2.31mg·mL-1. The maximum velocity (Vm) of EMNPS and EMNPS/SiO2were 0.04 and 0.038mg·mL-1·min-1, respectively.