Features of the kinetics of accumulating entomocidal exotoxins of Bacillus thuringiensis subsp. thuringiensis during fermentation stage of bitoxibacillin production

Accumulation of Bacillus thuringiensis subsp. thuringiensis beta-exotoxin (BET) in the course of industrial fermentation (a stage in the production of the entomocidal biopreparation bitoxibacillin) has been studied. It has been demonstrated in model experiments that the decrease in the content of BET in the culture fluid is accounted for by the toxin interaction with an attendant product, the exogenous metabolite (EM). EM has been isolated from the culture fluid and characterized. EM causes alkalization of the medium, exerts entomocidal effects (in Musca domestica) and fails to form salts on treatment with BaCl2. The absorption spectrum of EM is similar to that of BET, showing a maximum at lambda = 259 nm. The light-absorbing chromophore is a pyrimidine or purine base. A method for quantitative determination of both exotoxins (BET and EM) in bacterial preparations has been developed.