Optimization of cultivation conditions in banana wastes for production of extracellular β-glucosidase by Trichoderma harzianum Rifai efficient for in vitro inhibition of Macrophomina phaseolina

Abstract

The present study was carried out to optimize the physical and nutritional parameters for cultivation of Trichoderma harzianum Rifai for production of extracellular β-glucosidase, an alternative to chemcial fungicides to control Macrophomina phaseolina, which causes charcoal rot disease in crops. Response surface methodology by the Box–Behnken design (BBD) based on four factors (temperature, carbon sources, inoculum size and pH) was used for optimization of the cultivation conditions to produce β-glucosidase using agro-industrial banana wastes. The highest β-glucosidase activity (1483.27 U/mL) was attained under optimized cultivation conditions: ∼36 ºC and pH 7.3, using carbon source and inoculum size of 10% (w/v) and 5% (w/v), respectively. It is noteworthy that the low deviation values (0.09−0.44%) in the verification experiments (R1, R2 and R3) inferred the generated model was accurate to predict optimal cultivation conditions of T. harzianum Rifai. Likewise, the obtained diameters of inhibition zones ranging from 58.00−38.66 mm following treatment with β-glucosidase was found comparable to other in vitro tests using pure T. harzianum isolates and chemical fungicides. Hence, the findings indicated that it was feasible to use β-glucosidase as a greener alternative to chemical fungicides for control of M. phaseolina infection and consequently, for protection of crops against charcoal rot disease.