Commercial cellobiase has been immobilized in controlled pore silica particles by covalent binding with the silane-glutaraldehyde method with protein and activity yields of 67% and 13.7%, respectively. Thermal stability of the free and immobilized enzyme (IE) was determined with 0.2% w/v cellobiose solution, pH 4.8, temperatures from 40 to 70°C for free enzyme and 40 to 75°C for IE. Free cellobiase maintained its activity practically constant for 240 min at temperatures up to 55°C. The IE has shown higher stability retaining its activity in the same test up to 60° C. Half-lives for free enzyme were 14.1, 2.1 and 0.17 h at 60, 65 and 70°C, respectively, whereas the IE at the same temperatures had half-lives of 245, 21.3 and 2.9 h. The energy of thermal deactivation was 80.6 kcal/mol for the free enzyme and 85.2 kcal/mol for the IE, confirming stabilization by immobilization.
Thermal stability; immobilized enzyme; cellobiase; cellobiose
