Effect of corn-steep liquor on growth and mosquito larvicidal activity of Bacillus thuringiensis var israelensis de Barjac 1978 and B. sphaericus Neide 1904.

Influence of corn steep liquor on the cell yield and toxicity of three strains of B. thuringiensis var israelensis and two strains of B. sphaericus was studied and compared with peptone-yeast extract using a laboratory fermentor. Large increase in the cell yield of all the three strains of B. thuringiensis var israelensis was observed when cornsteep liquor was used as the sole nitrogen source. Significant increase in toxicity was also observed in B. thuringiensis var israelensis strains B17 and B113. Among the two B. sphaericus strains tested, the strain 1593 showed no significant change in cell yield and toxicity, whereas the strain VCRC B42 showed increased cell yield and toxicity in this medium. The results indicate that cornsteep liquor can effectively replace both peptone and yeast extract in the media presently used for large scale multiplication of the two larvicidal bacilli.