Production of Bacillus thuringiensis subsp. israelensis and Bacillus sphaericus strain 1593 on media using a byproduct from a monosodium glutamate factory

Two newly developed media, H4 and H7, were found to be highly suitable for culturing Bacillus thuringiensis subsp. israelensis and B. sphaericus, respectively. These media contained 0.05% K₂HPO₄ and 4% HDL (H4 medium) or 0.05% K₂HPO₄ and 7% HDL (H7 medium); HDL is the by-product from a monosodium glutamate factory. Tests to compare endospore formation and toxicity values of B. thuringiensis subsp. israelensis in H4 medium and nutrient broth supplemented with salts and glucose (NBSG) medium were carried out in a 3-liter fermentor. The viable cell count and LC₅₀ value of B. thuringiensis subsp. israelensis in H4 medium at 48 hr were 2.5 × 10⁸ cells/ml and 10^?7.2 (dilution), respectively, while those in NBSG medium were 1.6 × 10⁸ cells/ml and 10^?6.5, respectively. In the case of B. sphaericus grown in H7 medium, the number of cells and LC₅₀ value were found to be 1.4 × 10⁹ cells/ml and 10^?7.8, respectively. B. sphaericus grown in nutrient broth supplemented with salt and yeast extract (NBSY) were found to produce 6.4 × 10⁸ cells/ml and an LC₅₀ value of 10^?6.8. The toxicity of B. thuringiensis subsp. israelensis was tested against Aedes aegypti larvae, while that of B. sphaericus was tested against Culex quinquefasciatus. The cost of 10 liters of medium for production of B. thuringiensis subsp. israelensis and in B. sphaericus and H4 and H7 was $0.02 and $0.03, respectively. The cost of these newly developed media was much less than that of NBSG medium ($7.05 per 10 liters) for cultivation of B. thuringiensis subsp. israelensis and NBSY medium ($11.67 per 10 liters) for cultivation of B. sphaericus.