Solid-state fermentation in an earthen vessel: Trichoderma viride spore-based biopesticide production using corn cobs

The present study reports the production of Trichoderma viride spores in an earthen vessel using corn cobs. Using 4 kg of corn cobs, spore-based biopesticide was produced after 21 d with a maximum spore count of 2.50 × 10⁹ spores/g of substrate and a moisture reduction from 70.80% w/v to 8.10% w/v. The gas chromatography-mass spectrometry analysis of its ethyl acetate extract revealed that it had 20 secondary metabolites, of which 13 were known to be antimicrobial, one was plant growth-promoting, and one performed both functions. Dried extract dissolved in methanol showed the minimum fungicidal concentration of 5-10 mg/ml against Rhizoctonia solani on potato dextrose agar plate. Plate assays and pot experiments on Rhizoctonia solani-infected potato plants exhibited good antifungal and plant growth-promoting activities. The biopesticide showed 71.28% viability over 10 m of storage in the same earthen vessel at 30 ± 2 °C. Thus, a simple, robust technology was developed with good potential for farm deployment.