Production of mosquito larvicidal Bacillus thuringiensis serotype H‐14 on raw material media from Nigeria

Abstract

Bacillus thuringiensis serotype H‐14 de Barjac, a potent larvicide of many mosquito and blackfly species, was grown on various media compounded from fermented cassava (Mannihot esculenta), ground and whole maize (Zea mays) grains and whole cowpeas (Vigna unguiculata) in shake flask fermentations. The liquors obtained from 100g/l of the whole cowpea and maize grains as well as combinations of these were used for further fermentations in 1 and 5 1 fermenters. The final whole cultures obtained were bioassayed against L11/111 of Aedes aegypti and the concentration‐effects estimated. The potency of the preparations (estimated as LC50, strength that showed 50% mortality of the mosquito larvae) ranged from 10.5 mg/l for the 1:3 combination of cowpea steep liquor:maize steep liquor to 90 mg/l for the 2:1 combination at 95% confidence limits. The LC50 of a standard nutrient broth‐yeast extract medium was 18 mg/l. The juice of Citrus aurantifolia and an extract from Elaeis guiniensis were used as acid and alkali respectively while bleached deodorized palm olein was used as antifoam.