[Isolation and characterisation of an aflatoxin B1-degrading bacterium].

Aflatoxins are toxic and carcinogenic fungal metabolites. The aim of this research was to isolate aflatoxin B1 (AFB1)-degrading bacteria. Samples from various sources were screened by using coumarin as the sole carbon source. The strains that could grow in the medium with coumarin carbon source were detected for their degradation of AFB1 ability by addition of AFB1 (2.5 microg/mL) to the cultured broth. Among the positive strains, F4 strain with the highest activities was identified according to its morphological, physiological and biochemical properties together with phylogenetic analysis of its 16S rRNA sequence. The effects of degradation conditions such as bacterial cell concentration, pH, temperature, metal ions on the degrading AFB, were investigated. Ten isolates showed good AFB, reduction activity and they could grow well on coumarin carbon source. Strain F4, obtained from Budorcas taxicolor feces could reduce AFB1 by 90.03% after incubation in the liquid medium at 37 degrees C for 72 h. F4 was preliminary identified to be Pseudomonas stutzeri with morphology, physiological and biochemical properties and 16S rRNA gene sequence. The active degrading component existed in the cell of F4, and the degrading activity was interrelated with cell concentration, temperature, pH and metal ions. An AFB1-degrading strain F4 was isolated from animal feces and identified as Pseudomonas stutzeri. The activive component of AFB1 degradation was mainly in the cell of F4.