Thermal stability and energy of deactivation of free and immobilized cellobiase

Commercial cellobiase has been immobilized in controlled pore silica partic les by covalent binding with the silane-glutaraldehyde method with protein and activity yields of 67% and 13.7%, respectively. Thermal stability of th e free and immobilized enzyme (IE) was determined with 0.2% w/v cellobiose solution, pH 4.8, temperatures from 40 to 70 degreesC for free enzyme and 4 0 to 75 degreesC for IE. Free cellobiase maintained its activity practicall y constant for 240 min at temperatures up to 55 degreesC. The IE has shown higher stability retaining its activity in the same test up to 60 degreesC. Half-lives for free enzyme were 14.1, 2.1 and 0.17 h at 60, 65 and 70 degr eesC, 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/mo l for the free enzyme and 85.2 kcal/mol for the IE, confirming stabilizatio n by immobilization.