Production and Characterization of Cellulase and β-Glucosidase from a Mutant of Alternaria alternata

A mutant of Alternaria alternata excreted enhanced levels of carboxymethylcellulase and particularly beta-glucosidase when grown in cellulose liquid media. Both enzymes were purified two- to four-fold by ammonium sulfate precipitation and gel filtration, and the kinetic data showed K(m) values of 16.64 mg/ml of culture fluid for carboxymethylcellulase and 0.14 mM p-nitrophenyl-beta-d-glucoside and 0.81 mM cellobiose for beta-glucosidase at pH 5. Carboxymethylcellulase and extracellular beta-glucosidase functioned optimally at pH 5 to 6 and 4.5 to 5 and at temperatures of 55 to 60 and 70 to 75 degrees C, respectively. Both temperature optima and thermostability of beta-glucosidase were among the highest ever reported for the same enzyme excreted from cellulase and beta-glucosidase hyperproducing microorganisms.