Influence of carbon and nitrogen sources on the growth and sporulation of Bacillus thuringiensis var. tenebrionis

For knowledge localization of Bacillus thuringiensis (Bt) production as biological pest control, optimization of culture medium is necessary. In this study, Bacillus thuringiensis var. tenebrionis–BN1 (Btt–BN1) was used as a biological pesticide to control elm leaf beetles. The aim of optimizing the desire culture medium is to increase the production efficiency of Bt biopesticide using agricultural and food wastes as cheap raw materials. To optimize the parameters of the culture medium, experimental design of response surface methodology (RSM) was applied with a central composite design (CCD) approach. The parameters including the amount of carbon (sugar cane molasses, oats and wheat bran sources) and the amount of nitrogen (corn syrup source) at three levels (0.6 to 1 percent of sugar cane molasses, 0.3 to 0.9 percent of oat, 0.3 to 0.9 percent of wheat bran and 1 to 5 percent of corn syrup) were investigated with colony forming unit (CFU) response. The results obtained under operating conditions of pH = 7, temperature of 30oC after 72 hours. The results showed that the maximum CFU for the minimum concentration of oats (0.3%), the minimum concentration of wheat bran (0.3%), the maximum concentration of sugar cane molasses (1%) and the minimum concentration of corn syrup (1%) were equivalent to 8.36 11 spores.ml–1. In addition, the results of Btt–BN1 bioassay survey on elm leaf beetle showed that two concentrations of 0.5 and 1.0 percent cause 67.7% and 80.0% of mortality, respectively.