Production and Characterization of Highly Thermostable beta-Glucosidase during the Biodegradation of Methyl Cellulose by Fusarium oxysporum

Production of beta-glucosidase from Fusarium oxysporum was investigated during degradation of some cellulosic substrates (Avicel, alpha-cellulose, carboxymethyl cellulose (CMC), and methylcellulose). Optimized production of beta-glucosidase using the cellulosic substrate that supported highest yield of enzyme was examined over 192 h fermentation period and varied pH of 3.0-11.0. The beta-glucosidase produced was characterized for its suitability for industrial application. Methyl cellulose supported the highest yield of beta-glucosidase (177.5 U/mg) at pH 6.0 and 30 degrees C at 96 h of fermentation with liberation of 2.121 mu mol/mL glucose. The crude enzyme had optimum activity at pH 5.0 and 70 degrees C. The enzyme was stable over broad pH range of 4.0-7.0 with relative residual activity above 60% after 180 min of incubation. beta-glucosidase demonstrated high thermostability with 83% of its original activity retained at 70 degrees C after 180 min of incubation. The activity of beta-glucosidase was enhanced byMn(2+) and Fe2+ with relative activities of 167.67% and 205.56%, respectively, at 5mM and 360% and 315%, respectively, at 10 mM. The properties shown by beta-glucosidase suggest suitability of the enzyme for industrial applications in the improvement of hydrolysis of cellulosic compounds into fermentable sugars that can be used in energy generation and biofuel production.