Purification and Characterization of β-Glucosidase Produced by Aspergillus Terreus under Solid State Fermentation

Background: β-glucosidase is one of the important components of cellulase enzyme complex which acts synergistically with endoglucanase and exoglucanase to hydrolyze cellulosic substances into glucose. β-glucosidase is widely being used in biofuels, food, textile, cosmetics, leather, detergent, pulp, pharmaceutical and paper industries. It prevents the discoloration of fruit juices and helps in the enzymatic release of aromatic compounds from flavorless glucosidic precursors present in fruits and fermenting products. It has also several other potential applications including the increase of bioaccessibility of isoflavones in human intestine. Methods: Purification of β-glucosidase from Aspergillus terreus strain EMOO 6-4 was carried out in a two-step procedure; ammonium sulphate was used for the enzyme precipitation, then further separation occurs by gel filtration method using Sephadex G100. Characterization of the enzyme was carried out to determine the optimum incubation period, pH level, temperature of the enzyme activity and the effect of different concentration of the specific substrate on the enzyme activity. Results: The optimum reaction incubation period for maximum β-glucosidase activity produced by Aspergillus terreus strain EMOO 6-4 was 60 min. The optimum reaction pH and temperature were 5.5 and 35°C, respectively. The enzyme showed the highest activity at substrate concentration 0.0136 M. The enzyme is thermo stable up to 40 min at 50°C with calculated half-life of approximately 173.49 hours. The molecular weight of the purified β-glucosidase determined by SDS-PAGE was found to be 120 kDa. Conclusion: Aspergillus terreus strain EMOO 6-4 as wild isolate was found to be a good producer of β-glucosidase enzyme. The enzyme thermostability and high activity in an acidic pH (5.5) could find a profound use of the enzyme in saccharification of lignocellulosic wastes; that can help in final biodegradation of agricultural wastes to produce glucose as high energy source that can be used in different industries. Keywords: Aspergillus terreus, β-glucosidase, characterization, purification.