This study aimed to screen a bacterial strain with high detoxifying capability for aflatoxin B1 (AFB1), verify its biotransformation efficiency, and detoxification process. Three hundred and fifty samples collected from different environmental niche were screened using coumarin as the sole carbon source. HPLC was used to detect residues of AFB1, and 16S rRNA sequencing was performed on the isolated strain with highest AFB1 removal ratio for identification. The detoxified products of this strain were tested for toxicity in E. coli as well as LO2, Caco-2 and HaCaT human cell lines. HPLC-MS was applied to further confirm AFB1 removal and detoxification process. We identified a strain from plant leaf designated as DT with high AFB1-detoxifying ability that is highly homologous to Bacillus aryabhattai. The optimum detoxification conditions of this strain were 37°C and pH 8.0, resulting in 82.92% removal ratio of 2μg mL-1 AFB1 in 72h. The detoxified products were nontoxic for E. coli and significantly less toxic for the LO2, Caco-2 and HaCaT human cell lines. HPLC-MS analysis also confirmed the significant drop of the AFB1 characteristic peak. Two possible metabolic products, C19H15O8 (m/z 371) and C19H19O8 (m/z 375), were observed by mass spectrometry. Potential biotransformation pathway was based on the cleavage of double bond in the terminal furan of AFB1. These generated components had different chemical structures with AFB1, manifesting that the attenuation of AFB1 toxicity would be attributed to the destruction of lactone structure of AFB1 during conversion process.
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