Room temperature ionic liquid (RTIL)-decorated mesoporous silica SBA-15 for papain immobilization: RTIL increased the amount and activity of immobilized enzyme

Mesoporous materials, especially functionalized ones, have become a promising carrier for enzyme immobilization. We synthesized room temperature ionic liquid-decorated mesoporous SBA-15 (RTIL-SBA-15) for papain immobilization. The results of powder XRD, IR and N-2 adsorption-desorption isotherms have confirmed that ionic liquid [Simim(+)][Cl-] was successfully grafted on the surface of SBA-15. As a consequence of the electrostatic attraction between the cation [Simim(+)] and the negatively charged papain. RTIL-SBA-15 had an advantage over SBA-15 when papain was immobilized at pH = 9.00. The kinetic study showed that the interaction between papain and the carrier was stronger after ionic liquid modification. In the casein hydrolysis, the papain immobilized on RTIL-SBA-15 showed a higher specific activity than that on SBA-15, implying that the ionic liquid [Simim(+)][Cl-] was beneficial to improve the activity of the immobilized papain. The optimum pH of the immobilized papain was shifted to higher than that of free enzyme. (C) 2011 Published by Elsevier B.V.