LAUSR

Abstract In this study, Bacillus thuringiensis var. tenebrionis-BN1 (Btt-BN1) was used as an effective bio-pesticide against elm leaf beetles. Statistical experimental design was applied for optimization of the culture media in order to achieve high level of colony forming unit (CFU) response from Btt-BN1. The response surface methodology (RSM) was used to optimize the parameters of the culture medium. Carbon source value, nitrogen source value, and carbon source type parameters were evaluated at five levels regarding CFU response. The results at operating condition of pH = 7 and temperature of 30° C after 72 h indicated that the maximum CFU of 4.85 × 107 spores.ml−1 (for sugar cane molasses) was achieved at the minimum nitrogen source (less than 2%v), at the maximum carbon source (above 11%v), and the optimal C/N ratio of 5.0. Moreover, the results of model validation indicated the CFU response for sugar cane molasses of 6.34 × 107 spores.ml−1. The results of Btt-BN1 bioassay on elm leaf beetle showed that two concentrations of five and 10 per thousand cause 66.7% and 80.0% mortality, respectively.