optimizations of bacillus thuringiensis native isolate (6r) production in lab fermenter

biological control plays a very important role in pest management. bacillus thuringiensis ber. has been widely used as a biological control agent in over 60% of microbial-based pesticides and moreover, its gene inducing pest resistance has been used in the production of a large number of transgenic plants (bt-crops). the successful performance of some of these bt-based bio-pesticides depends on the concentration of delta endotoxin and spores in the final product. the medium composition and the conditions under which the bacteria are grown strongly influence these concentrations, therefore, this study was set to optimize bt growth conditions, i.e. ph, temperature and aeration rate. to reduce the number of experiments, taguchi statistical method and qualitek 4 were used. the results showed that the optimum conditions leading to the highest bacterial spores of 1.50 × 1012 were the temperature of 28 ° c, ph of 5.7, and oxygen saturation of 80%. based on the results obtained, the highest and the lowest interactions among the process parameters were at 39.92% and 0.25% for temperature/aeration rate and temperature/ph, respectively.