Stability and catalytic properties of encapsulated subtilisin in xerogels of alkoxisilanes

Abstract

Subtilisin was encapsulated in glass sol-gel matrices using alkoxysilane precursors of different chain lengths. The entrapment efficiency of the sol-gel glass was about 80%. The resultant glass enzyme had the same optimum pH of 7.0, but the optimum temperature was shifted to a higher temperature of 60 degrees C. The biocatalyst sol-gel particles retained 50% of the original activity even after 11 cycles of repeat use. The scanning electron micrograph of the immobilized enzyme showed uniform round particles of 5-20 mu m. The specific surface area by BET measurement of the immobilized subtilisin in vinyl tri methoxy silane (VTMS) was found to be 38 m(2) g(-1). This immobilized enzyme was useful for the synthesis of peptides either in a mixture of acetonitrile: dimethyl formamide (DMF) or in 1-butyl 3-methyl imidazolium hexaflurophosphate, an ionic liquid. The formation of dipeptides and tripeptides Of L-alanine was confirmed by TLC, HPLC and FT-IR analysis.