Influence of temperature and pH on cellulase activity and stability in Nectria catalinensis

The influence of temperature and pH on the activity and stability of the cellulase system (endoglucanase, exoglucanase and cellobiase) was investigated in Nectria catalinensis. Optimal temperature for the activity of the cellulase system ranged from 50 to 55 degrees C, with an optimum for stability between 23 degrees C and 37 degrees C after a 72 h incubation period. For the different enzymes, maximal activity was registered between pH 4.2-5.8, with pH 4.8 being close to optimal for all stability studies. The activation energy was 4.97 Kcal mol-1 for endoglucanase, 4.37 Kcal mol-1 for exoglucanase and 13.73 Kcal mol-1 for cellobiase. The K(m) and Vmax values were 1.73 mg CMC ml-1 and 0.45 mumol glucose min-1 mg protein-1 for endoglucanase, 0.22 mg microcrystalline cellulose ml-1 and 57.1 nmol glucose min-1 mg protein-1 for exoglucanase, and 2.95 mM cellobiose and 0.17 mumol glucose min-1 mg protein-1 for cellobiase.