Screening and Identification of Aflatoxin B₁ Degradation Strain

The degradation bacteria were isolated from the soil in Qingdao by screening with coumarin as the only carbon source,and the highly efficient strain A6 was further identified. The supernate,bacterium suspension and intracellular fluid of the strain A6 were separated and the degradation characteristics of AFB₁ were analyzed. The strain was identified by morphological characteristics,physiological,biochemical characteristics and 16S rRNA gene. The results indicated that the strain A6 could efficiently degrade AFB₁.The supernate,bacterium suspension and intracellular fluid could degrade 90.6%,19.6% and 12.8% of AFB₁,suggesting that the degradation activity of strain A6 was located in extracellular fluid. On the plate,the strain colony was milky white with wrinkles and gram stain was positive. The strain could assimilate glucose,arabinose,lactose and other carbon sources. Analysis of the 16S rRNA gene showed that the similarity between strain A6 and Bacillus velezensis CR-502^T was 99.64%. Based on the morphology,physiological and biochemical characteristics,and the analysis of 16S rRNA gene sequence homology,the strain A6 was identified as Bacillus velezensis. The results provided a foundation for further study on the degradation mechanism of this bacterium.