Spray-dried Bacillus thuringiensis Serovar israelensis formulations for control of Aedes aegypti larvae.
Suspensions containing 0.25 and 1.25 g/liter of Bacillus thuringiensis subsp. israelensis (Bti) spore-toxin complex were spray-dried by using maltodextrin DE-6, corn starch, and nixtamalized corn flour (25 g/liter) as materials to entrap active delta-endotoxin. The inlet air temperature of the drier was kept constant at 141 degrees C and the outlet temperature was maintained at 60 or 70 degrees C. The Probit analysis of the concentration-mortality response of third instars of Aedes aegypti (L.) larvae of the spray-dried products at 60 degrees C showed that LC50 values for maltodextrin DE-6 with 1 and 5% spore-toxin complex were 4 and 10% higher in toxicity, respectively, than that for the unformulated spore-toxin complex without drying. The LC50 value for corn starch with 1 and 5% of spore-toxin complex were also higher in toxicity (7 and 8% respectively). However, LC50 values for nixtamalized corn flour with one and 5% spore-toxin complex were 81 and 55% higher in toxicity, respectively. Dried products contain an a(w) < or = 0.7, suggesting that they are able to keep the products without microorganism growth for longer periods. The scanning electron microscope of Bti spray-dried formulations with nixtamalized corn flour showed smooth spherical particles entrapping the active ingredient. These results suggested that Bti spore-toxin complex formulated with maltodextrin DE-6, corn flour, and nixtamalized corn flour, and then spray-dried may increase larval feeding and thus increase activity against Ae. aegypti larvae.
Ramírez-Suero
Montserrat
M
Unidad de Investigación y Desarrollo en Alimentos, Instituto Tecnológico de Veracruz Mexico.
Robles-Olvera
Victor
V
Ramírez-Lepe
Mario
M
D000330:Aedes / Q000254:growth & development*; D000818:Animals; D001413:Bacillus thuringiensis; D001427:Bacterial Toxins / Q000008:administration & dosage; D007306:Insecticides / Q000008:administration & dosage*; D007814:Larva; D008855:Microscopy, Electron, Scanning; D009032:Mosquito Control / Q000379:methods*
D001427:Bacterial Toxins; D007306:Insecticides