Production of concentrates of bacterial bio-insecticide Bacillus thuringiensis var. israelensis by flocculation/sedimentation

Flocculation/sedimentation of Bacillus thuringiensis var. israelensis (Bti) using flocculating agents has been studied. Batch cell production was performed in an agitated tank, and the flocculation assays were carried out in jar tests. Flocculent suspensions were characterized based on diameter of flocs and density. The best results were obtained with CaCl2•2H2O, FeCl3•6H2O, Al2(SO4)3 and tannin, with optimal flocculation concentrations of 2500, 2500, 3500 and 1000 mg l−1, respectively. Thickening of the flocculent suspensions was investigated, leading to determination of the capacity curves of the settler. Bioassays against Aedes aegypti larvae demonstrated excellent results in insect control.