Abstract: Aflatoxin B₁ (AFB₁) is a common mycotoxin in moldy cereal grains and feedstuff,which seriously threaten their use and economic value.It is important to study detoxification of AFB₁ in grains and feedstuff.In this study,nine microbial strains with AFB₁ degradation capacity of above 60% were screened using medium containing coumarin as the sole carbon source.One of which,named YM-1,had the AFB₁ degradation capacity of 91.48%.The sequence alignment of 16S rDNA of the YM-1 strain demonstrated that it was Pseudomonas aeruginosa.The degradation dynamics of AFB₁ by P.aeruginosa YM-1 showed that 90.70% of AFB₁ in NB medium was degraded after 96 h and the degradation rate of AFB₁ was the highest between 24 h to 48 h.The AFB₁-degrading activity of P.aeruginosa was predominantly attributed to the cell-free supernatant and the P.aeruginosa cell could also adsorb AFB₁.The AFB₁-degrading activity in the cell-free supernatant was found sensitive to proteinase K and heat treatments,indicating that the extracellular enzymes are responsible for the AFB₁ degradation.Solid state fermentation of the P.aeruginosa YM-1 in moldy corn powder was performed and 88.87% of AFB₁ in corn powder was reduced after 6 days.This study provides an experimental basis for the detoxification treatment of AFB₁ contaminated cereal grain and feedstuff by P.aeruginosa.