Immobilization of lipase onto mesoporous silica KIT-6 and montmorillonite K10 for enzymatic hydrolysis of tributyrin

Abstract

Mesoporous silica KIT-6 and montmorillonite (MMT) K-10 clay were prepared and used for immobilization of the enzyme, Candida rugosa lipases (CRL), aiming at their use as biocatalysts for the hydrolysis of tributyrin. Immobilization of the enzymes onto the supports was performed by physical adsorption using 0.1 M phosphate buffer solutions (pH 7) as the dispersion medium. The activity of the immobilized CRL for tributyrin hydrolysis was investigated at incubation temperature of 40 °C during 120 min and different concentration of the lipase solution for both the supports. Characterization by XRD showed that the long-ranged ordering in the KIT-6 and crystallinity of the MMT K-10 material were affected slightly by the lipase immobilization. This result gives an indication to the present of lipase-support interaction in the immobilized lipase system. Additionally, the results of FTIR spectroscopy verified the presence of silanols on the surfaces of MMT K-10 and KIT-6 materials, while the nitrogen adsorption data showed the resulting immobilized enzyme catalysts were rendered porous, with the KIT-6 giving higher specific surface areas and higher pore diameters in a narrow distribution of sizes ranging from 4 to 12 nm. The immobilization of CRL on KIT-6 and MMT K-10 through hydrogen bonding with the silanol groups, led to an increase in the hydrolysis activity compared to that of free lipase. However, the activity of KIT-6 immobilized CRL was higher than was observed on MMT K-10 immobilized CRL. Furthermore, lipase immobilized on mesoporous silica KIT-6 was shown to be recyclable up to 5 times in aqueous medium. The high surface area and the unique pore system of the mesoporous silica KIT-6, having may be the crucial factors that play an important role in retaining the enzyme in the support, and consequently, improving the lipase activity and stability.