immobilization of subtilisin carlsberg on modified silica gel by cross-linking and covalent binding methods

proteases are important enzymes that their role in various industries is undeniable. however, keeping enzymes stable during its activity in harsh conditions is so important. in this study, protease enzyme was immobilized on the porous silica particles and its stability in different temperatures and phs was evaluated. first silica particles were aminated by 3-aminopropyltriethoxysilane then the protease enzyme was immobilized on the modified silica by glutaraldehyde cross-linking method and the immobilized enzyme’s activity was maintained for more than 40 days. measuring the free subtilisin carlsberg enzyme activity and immobilized enzyme was performed according to the lowry method. in another part, the effects of different phs and temperatures on free and immobilized protease were evaluated. the immobilized protease activity was measured in temperature range between 25-75◦c and ph range 6.5-12. the absorption was read in 660nm. it is shown that the optimum temperature for immobilizaed enzyme is 50°c. the results showed that immobilized protease is more stable than free protease.