Active biocatalysts based on Candida rugosa lipase immobilized in vesicular silica
Vesicular silica (VS) with hierarchical structure was prepared by utilizing cationic surfactant cetyltrimethylammonium bromide (CTAB) and anionic surfactant sodium dodecyl sulfate (SDS) as the structure directing agents, and 1,3,5-triisopropylbenzene (TIPB) as the micelle expander. The resulting unilamellar and multilamellar VS with interlamellar mean mesopore size of 15–20 nm and shell thickness of 5–15 nm were used as supports for immobilization of Candida rugosa lipase (CRL) through physical adsorption. Possible mechanisms for the formation of VS and the immobilization of CRL on VS are proposed. N2 adsorption-desorption experiments and Fourier transform infrared spectroscopy (FT-IR) measurements demonstrated that CRL was adsorbed into the curved channels of the VS. The catalytic activity, thermal stability, and reusability of VS immobilized CRL were assayed in phosphate buffer medium by hydrolysis of triacetin. The effects of pH and temperature on enzyme activity were also investigated. We report that VS immobilized CRL exhibited outstanding adaptability at higher pH and temperature, and excellent thermal stability and reusability compared with free CRL.
► The structural characteristics of two vesicular silica prepared with or without 1,3,5-triisopropylbenzene are compared. ► Mechanisms for formation of vesicular silica and immobilization of Candida rugosa lipase on vesicular silica are proposed. ► Loading amount and activity of vesicular silica-1 are higher than those of vesicular silica-0. ► Optimal pH and temperature for vesicular silica immobilized C. rugosa lipase are superior over those of C. rugosa lipase. ► Vesicular silica-1-C. rugosa lipase showed higher thermal stability and reusability than vesicular silica-0-C. rugosa lipase.
Journal: Process Biochemistry - Volume 47, Issue 6, June 2012, Pages 953–959