The Studies On The Bioactive Substance Obtained From Fermentation Supernation Of Bacillus Thuringiensis

In this paper, the bioactive substance, which inhibits the growth of some kinds of microorganisms, in the supernatant of fermentation broth produced by our China's Bacillus thuringiensis MP-342 was studied. Results showed that the bioactive substance is one kind of water-soluble ,heat-stable and alkaline substance; Microorganism inhibition experiment indicated that the substance inhibited some kinds of crop pathogenesis fungi.First, the culture conditions of Bacillus thuringiensis MP-342 and the method of detecting bioactive substance were established. After studying the effects of different carbon sources, nitrogen sources, inorganic salts on the biosynthesis of the bioactive substance by Bacillus thuringiensis MP-342 , the optimal fermentation medium ingredients were determined.According to the yield of the bioactive substance obtained finally, the optimal fermentation parameters were determined as following: seed age(18h), inoculation column(7%), fermentation temperature (30℃), and the fermentation time(32h) was determined according to the fermentation curve.By measuring the diameters of inhibition zones of known control samples with different concentrations, a relation of bioactive substance content to the diameters of inhibition zones was determined and a formulation was obtained, so that the bioactive substance in the supernatant of samples can be measured correctly and quantitatively.In addition, the separation and extraction conditions for the bioactive substance were studied, and a separation process was established basically. After testing the inhibition effects of the substance on some microorganisms, it was found that six kinds of plant pathogenic microorganisms were quite sensitive to the substance.Finally, the properties and structure of the substance were analyzed. Results showed that the bioactive substance was heat-stable, tolerant to weak acid and weak alkali. By mass spectrum analysis, this substance was elementarily presumed as the part of same configuration as zwittermicin A, reported overseas.