Evaluation of the Growth Pattern of Bacillus thuringiensis BtIII in Different Media Containing Low-Cost Agro-Industrial Based Carbon Sources

Synthetic pesticides have a number of ill effects on soil, water, human health, wildlife and ecological balance. These ill effects have led to the use of microbial insecticides against insect pests of order Lepidoptera, Coleoptera, Diptera and Hemiptera. Bacillus thuringiensis is a gram-positive endospore forming bacterium that produces a parasporal crystal protein inclusion during sporulation that is insecticidal to insect pests of various orders. An attempt has been made to develop low-cost Bacillus thuringiensis formulations for the management of Helicoverpa armigera, which is a major problem in cotton, gram, vegetables and other crops. Agro-industrial residues and their byproducts can be used for the large-scale production of B. thuringiensis biomass to reduce the cost of production of these bio-pesticides. Different low-cost agro-industrial based carbon sources such as potato extract, cornstarch, wheat flour, sugarcane molasses, barley flour and soluble starch were evaluated for Bacillus thuringiensis biomass production. The media containing different carbon sources were inoculated with Bacillus thuringiensis strain BtIII and kept under submerged conditions. The growth pattern was observed by plate count and absorbance method. Among the different carbon sources evaluated, maximum biomass of B. thuringiensis BtIII was achieved after 48h of growth in the medium containing 1.2% potato extract in basal medium. The biomass production in this medium was equivalent to that achieved in LB medium after 48h of growth.