Biological pesticide production by Bacillus thuringiensis using wastes of starch industry

Some wastes especially wastes of food industries need to be treated in order to recover some value-added products. One of these valuable products is biological pesticides. Today, the most successful biological pesticides are produced by Gram-positive, rod-shape bacteria, the genus Bacillus that produces crystalline endotoxin proteins during spore formation. These toxins will be activated when they enter the insect intestine under alkaline condition and will damage the cell membrane and make holes in the membrane which result in lysing of epithelial cells. In this research, the waste of starch producing industry was inoculated with Bacillus thuringiensis var. kurstaki and then the crystalline protein with MW of 65 KDa was produced during fermentation. The larvaes of Galleria melonella were treated to this protein and the rate of mortality was assessed after 24 and 48 h, and its effect was compared with that of control. Researches showed that the production of delta endotoxin has direct correlation with sporulation. The most toxicity of these bacterial proteins occurs at the highest number of spores. Thus, the number of total bacteria and their spores were enumerated using PCA during fermentation that was 12.5×108 and 48×107 cfu/ml, respectively.