Coconut water as a cheap source for the production of δ endotoxin of Bacillus thuringiensis var. israelensis, a mosquito control agent

Bacillus thuringiensis var. israelensis (B. t. i.) is being widely used in mosquito control programs. However, the large-scale production of this bacillus is expensive due to the high cost of the production medium. In this study, we attempted to develop a cost-effective medium, based on a locally available raw material namely coconut water which is available in plenty as waste product from coconut oil industry. The yield of cell mass, sporulation and mosquito larvicidal activity were studied by growing this bacterium in this waste product and in comparison with the conventional medium (NYSM). Cell mass yield of 3.1 g/L, spore count of 3.4 × 1011 spores/mL and mosquito larvicidal activity (LC50) of 14.85 ng/mL (against early fourth-instar larvae of Aedes aegypti) were obtained with a 30 h old culture of this bacterium grown in coconut water. This is almost similar to that obtained with NYSM medium. Hence, coconut water-based culture medium is economical for the production of B. t. i.