A cost-effective medium for the large-scale production of Bacillus sphaericus H5a5b (VCRC B42) for mosquito control

Bacillus sphaericus has been widely used in mosquito control programs, but the large-scale production of this bacterium is expensive because of the high cost of the medium. In this study, we attempted to develop a cost-effective medium, based on inexpensive, locally available raw materials including soybean flour (Glycine max) and peanut cake powder (Arachis hypogea) by using 100-l bioreactor. Sporulation, toxicity and biomass were satisfactory after B. sphaericus was produced on both media. Use of the soybean culture medium resulted in “maximum” toxicity (LC50 14.02 ng/ml against third instar Culex quinquefasciatus larvae), highest spore count (3.7 × 109 spores/ml) and maximum biomass (4.6 g/l) within a short fermentation time of 21 h. Hence, this soybean-based culture medium was considered most economical for the large-scale industrial production of B. sphaericus.