Production of β-glucosidase on solid-state fermentation by Lichtheimia ramosa in agroindustrial residues: Characterization and catalytic properties of the enzymatic extract

Background: β-Glucosidases catalyze the hydrolysis of cellobiose and cellodextrins, releasing glucose as the main product. This enzyme is used in the food, pharmaceutical, and biofuel industries. The aim of this work is to improve the β-glucosidase production by the fungus Lichtheimia ramosa by solid-state fermentation (SSF) using various agroindustrial residues and to evaluate the catalytic properties of this enzyme. Results: A high production of β-glucosidase, about 274 U/g of dry substrate (or 27.4 U/mL), was obtained by cultivating the fungus on wheat bran with 65% of initial substrate moisture, at 96 h of incubation at 35°C. The enzymatic extract also exhibited carboxymethylcellulase (CMCase), xylanase, and β-xylosidase activities. The optimal activity of β-glucosidase was observed at pH 5.5 and 65°C and was stable over a pH range of 3.5-10.5. The enzyme maintained its activity (about 98% residual activity) after 1 h at 55°C. The enzyme was subject to reversible competitive inhibition with glucose and showed high catalytic activity in solutions containing up to 10% of ethanol. Conclusions: β-Glucosidase characteristics associated with its ability to hydrolyze cellobiose, underscore the utility of this enzyme in diverse industrial processes.