Stability and catalytic properties of encapsulated subtilisin in xerogels of alkoxisilanes Original Research Article

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 °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 μm. The specific surface area by BET measurement of the immobilized subtilisin in vinyl tri methoxy silane (VTMS) was found to be 38 m2 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.