Synergisitic Effect of Chitinases and Bacillus Thuringiensis israelensis Spore-Toxin Complex Against Aedes aegypti Larvae

Abstract Six subspecies of Bacillus thuringiensis Berliner (Bt) were grown in minimal medium with chitin as the sole carbon source for 6 days to obtain Bt cell-free fermented broths, which were then evaluated for chitinolytic activity and tested against third-instar Aedes aegypti (L.) (Diptera: Culicidae) larvae. Bt Pakistani showed the highest chitinolytic activity (approximately >2700 mU/mL), Bt kurstaki showed the lowest activity (approximately <2000 mU/mL), and Bt thompsoni, Bt aizawai, Bt israelensis, and Bt alesti showed intermediate activities (approximately 2100–2400 mU/mL). Bt aizawai and Bt thompsoni broths showed the highest toxicity (LC50) against third-instar A. aegypti larvae (approximately <290 mU/mL). Bt kurstaki broth showed the lowest toxicity (approximately 420 mU/mL), while Bt pakistani, Bt israelensis, and Bt alesti broths showed intermediate toxicities (approximately 360–460 mU/mL). A purified and biochemically characterized Bt aizawai chitinase and commercial chitinases (from Serrat...