[Effect of mineral salts on exotoxin formation and productivity of a Bacillus thuringiensis culture].

The effect of ten mineral salts on the productivity and toxin synthesis was studied in Bacillus thuringiensis IPM-1140. Exotoxin synthesis was stimulated by Zn2+, Mn2+ and NH4+ ions as well as by potassium phosphates. The direct correlation between the number of viable spores and the exotoxin accumulation was disordered at extreme salt concentrations. Optimal salt concentrations in the yeast-polysaccharide medium were found using the method of a fractional factor experiment, which made it possible to increase the productivity of the culture to 5 X 10(9) spores/ml and the yield of the exotoxin to 730 micrograms/ml. The thermoresistance and the entomopathogenic activity of crystals increased when B. thuringiensis IPM-1140 was grown in this medium.