The current study evaluated the production and characterization of β-glucosidase by the thermophilic fungus Thermomucor indicae-seudaticae in solid-state fermentation of wheat bran. Isolated fungi have significant amounts of β-glucosidase, an enzyme that may be applied to different industrial processes, such as the production of fuels, food, and other chemical compounds. Maximal enzyme activity occurred in pH 3.5-4.5 and at 70 °C. The enzyme exhibited high thermostability, for 1 h, up to 60 °C, and good tolerance to glucose (10 mM) and ethanol (10%). The optimization of fermentative parameters on the production of β-glucosidase was carried out by evaluating the best supplementary nutrient source, pH of nutrient solution, initial substrate moisture and fermentation temperature. The optimization of the above fermentation parameters increased enzyme activity by 120.0%. The highest enzymatic activity (164.0 U/g) occurred with wheat bran containing 70% initial moisture, supplemented with 1.0% (NH4)2SO4 solution at pH 5.5-6.0 and fungus incubated at 40 °C. A more detailed study of β-glucosidase suggested that Sulfur is an important component of the main amino acid present in this enzyme. The enhancer of the enzyme activity occurred when the fungus was grown on wheat bran supplemented with a sulfur-containing solution. In fact, increasing the concentration of sulfur in the solution increased its activity.
Keywords: solid-state fermentation; sulfur; wheat bran; β-glucosidase.