The utilization of local carbon and nitrogen source for the production of Bacillus Thuringiensis Subsp. Aizawai as the active ingredient of bioinsecticide

Abstract

The effect of concentrations of nitrogen sources in the media formulation containing 1.25% molasses as the carbon source on the production of spore- crystal mixture (active ingredient of bioinsecctiside) by Bacillus thuringiensis subsp. aizawai was investigated. The nitrogen sources tested were soybean flour in the concentration of 0.5, 1.0, 1.5, 2.0, and 2.5%, and fish meal in the concentration of 0.35, 0.7, 1.05, 1.4, and 1.75%. Among the various concentration tested 1.5% soybean flour or 1.05% fish meal was found to be optimum. Both were found to produce the highest cell concentration and more than 90% of the cells in the cultures underwent lysis after 48 hours of fermentation, releasing their spores and crystal into the media. Furthermore, the concentration of 1.5% soybean flour or 1.05% fish meal in the media produced dryweights of spore-crystal mixtures (lyophilized in the presence of 26.08 g lactose) as much as 30.35 and 29.42 g/l, viable spore counts of 2.83 x 108 and 2.27 x 108 VSC per mg dryweight of spore-crystal mixture, and LC50 values (against the first-instar larvae of Spodoptera litura) of 387.78 and 431.03 ^ig/ml, respectively.