Optimization of bio-insecticide production by Tunisian Bacillus thuringiensis israelensis and its application in the field

•Delta-endotoxins from BUPM98 are highly active against mosquito larvae.•Gruel and soybean meal had been chosen for the production of BUPM98 toxins.•Culture medium based on local agricultural by-products is optimized.•Improvement of delta-endotoxin production about 30% compared to the basal medium.•The application of BUPM98 fermentation product in an open field was proven efficacy.