Isolation、Screening And Aflatoxin B₁-degrading Of The Strain Antagonist To Aspergillus Flavus

Feed in the process of production and processing and transport easily contaminated with mold, mold contamination of feed destroy the nutrients and the mold produces the toxins which affect the safety and health of human being through the food chain. The common toxin is aflatoxin which is strongest and the most widespread. There are some method to prevent aflatoxin which are physical method, chemical method and biological method. It becomes a hot research in domestic and foreign.In our experiment, it used the plate confrontation screening and rescreening inhibitory rate method to isolated from soil and the mold contamination of grain. Using the morphological, physiological, biochemical and 16 S r DNA sequence analysis of the strain of N2, it is identified as Bacillus amyloliquefaciens. Using the toxicity test, it determines that the strain of N-2 has no toxin. The strain of N-2 changes the hyphae shape of Aspergillus flavus and reduces spore germination and inhibit the growth of Aspergillus flavus. The mycelia of N-2 becomes thick and short, internal protoplast of mycelium uneven distribute, the spore germination rate is 81.08%. The strain N-2 inhibition active component analysis find the inhibition of fermented liquid of N-2 and no N-2 supernatant was significantly higher than cell suspension and intracellular fluid, the others were no difference(P > 0.05). Therefore, the extracellular secretions of strains of N-2 may inhibit the growth of Aspergillus flavus. Strains of N-2 fermented liquid can degradate Aflatoxin B1(AFB1 Aflatoxin B1,), the degradation rate was 37.81%.Microbes in the mouth into the gastrointestinal tract to tolerance to low p H and intestinal bile salt in the hypertonic environment to play the antagonist role. The test results show that, the simulated gastric juice strain N-2 4 h, the living bacteria number of 96.11%. The simulated bile salt treatment strain N-2 24 h, its viable bacteria number reached 95.68%. The inhibition effect of strain N-2 on E. coli, Salmonella and Shigella was inhibited, and the diameter of antimicrobial ring was 19.57 mm, 18.39 mm, 17.92 mm.In our experiment the separation screening N-2 strains of broilers fed with test, through the detection of broiler growth performance, blood biochemical index and organ tissue, study the different doses of N-2 strain fermentation broth of broiler feed in Aspergillus flavus toxin and antagonistic effect of degradation. Experimental results show that the basal diet per kilogram added 0.2 L strain N-2 fermentation liquid can improve the toxicity of AFB1 in broilers, reduces the toxins to the liver injury and to maintain the balance of intestinal microflora of broilers.The results show that the separation screening solutions from Bacillus amyloliquefaciens N-2 on Aspergillus flavus has significant inhibitory effect, the safe and nontoxic, on gastric acid and bile salt have tolerance and can reduce the toxicity of AFB1 on animals, for the development of Aspergillus flavus, Aspergillus flavus toxin biological control agents provided theoretical foundation and experimental basis.