Abstract: The aim of this study is to screen out strains that can efficiently degrade aflatoxin B₁ (AFB₁), and to investigate the detoxification effect of its detoxification active components. In this study, the target bacteria were primarily screened by coumarin as the sole carbon source, and rescreened based on the degradation ratio of AFB₁.The selected strain was identified by morphological observation, physiological and biochemical tests, and 16S rDNA sequence analysis. The detoxification active components produced by the bacteria were located by measuring the AFB₁ degradation rate of the different fermentation components. The cytotoxicity of AFB₁degradation products to LMH cells was analyzed by CCK-8 method. And the effects of heat treatment, ultraviolet radiation, strong acid, strong alkali and proteinase K treatment on the detoxification effects of active ingredients were also studied. The results showed that 24 bacteria strains could grow well in the primary screening medium. After detoxification re-screening, strain Y1-B1 could efficiently degrade AFB₁, and its degradation ratio of AFB₁ reached 73.2%. Through morphological observation, physiological and biochemical tests and 16S rDNA sequence analysis, this strain Y1-B1 was identified as Bacillus amyloliquefaciens. Studies on the detoxification activity of different fermentation components of the cultures of strain Y1-B1 showed different degradation rate of AFB₁, with the supernatant of cell culture exhibited the strongest detoxification activity, followed by bacterial lysates, suspension of bacteria, and supernatant of bacterial lysate. The results demonstrated that the detoxification active components of Bacillus amyloliquefaciens Y1-B1 was an extracellular product in the supernatant. The results of cytotoxicity showed that the toxi-city of AFB₁ degraded by the detoxification active components was significantly reduced compared with the toxicity of AFB₁ to LMH cells. The detoxification active components present different performances to different physical and chemical factors, and has strong resistance to high temperature and ultraviolet radiation, relatively poor resistance to strong acids and strong bases, and proteinase K only partially weakens the detoxification ability. This study will provide new microbial germplasm resources for solving the problem of aflatoxin pollution and also lay foundation for the development of subsequent microbial detoxification products.

Key words: aflatoxin B₁, Bacillus amyloliquefaciens, detoxification active components, detoxification effect, cytotoxicity