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

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Abstract
A mutant of Alternaria alternata excreted enhanced levels of carboxymethylcellulase and particularly β-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 Km values of 16.64 mg/ml of culture fluid for carboxymethylcellulase and 0.14 mM p-nitrophenyl-β-d-glucoside and 0.81 mM cellobiose for β-glucosidase at pH 5. Carboxymethylcellulase and extracellular β-glucosidase functioned optimally at pH 5 to 6 and 4.5 to 5 and at temperatures of 55 to 60 and 70 to 75°C, respectively. Both temperature optima and thermostability of β-glucosidase were among the highest ever reported for the same enzyme excreted from cellulase and β-glucosidase hyperproducing microorganisms.