Laboratory Study of Microbial Insecticide Produced by the Bacteria Bacillus thuringiensis of Starch Factory Sewage for Biological Control of Larvae Culex pipiens

 Background & Objective: Epidemic of dangerous diseases caused by Culex pipiens’ bites prompted us to focus on these groups of insects. Today, the most successful biological insecticides are produced by the bacteria of the genus Bacillus, which in the production phase of spores, makes crystalline endotoxin protein. This protein can be activated upon entering the insect’s intestine in alkaline condition and damage the membranes of the intestine cells. Sewage obtained from food factories is required for the production of such valuable biological insecticides. We sought to utilize the sewage from a starch factory in order to produce biological insecticides by Bacillus thuringiensis in the lab. Materials & Methods: In this study, Bacillus thuringiensis (H14) was grown on sewage from a starch factory. During fermentation, crystalline proteins with a molecular weight of 65 kDa were produced. The proteins, produced on the insect larvae of Culex pipiens, were thereafter tested, and mortality rates after 24h and 48h were evaluated and compared with those of control samples.  Results: The total numbers of bacteria and spores produced in agar plates during fermentation were 12/5×10 8 and 48×10 7 colonies per ml, respectively.  Conclusion: This study showed that the production of delta endotoxin is correlated with the phase of spore production, and the highest toxicity effect of crystal proteins is in the highest density of spores.