Utilization of Immobilized Trypsin on Commercial Silica Gel as Catalyst

G. Hodaifa and M. D. Romero

Abstract
In this study, trypsin was immobilized onto commercial silica gel and the transesterification of N-acetyl-L-tyrosine ethyl ester (ATEE) and 1-propanol in an organic solvent was used as a model reaction. The amount of trypsin adsorbed onto the support affected the time required to achieve full conversion. The concentration of immobilized trypsin that provided a maximum yield of product in a minimal amount of time was 43 μmol of trypsin/g silica gel. At the end of transesterification reactions, the turnover frequency (9.3 · 10–5 to 6.8 · 10–3 s–1) and turnover number (8 to 520) of transesterification markedly increased when the initial concentration of the substrate had increased from 0.8 to 100 mmol L–1. The kinetic parameters Km (64.8 mmol L–1 ATEEinitial) and Vmax (0.364 mmol L–1 ethanol min–1) were determined. The immobilized trypsin maintained enzymatic activity and reusability after one month of storage at 4 °C.

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Keywords
transesterification, trypsin, enzyme immobilization, silica-gel