AFB₁ degrading bacteria:Isolation, identification, optimization of its degradation conditions and toxicity evaluation of its degradation products

【Objective】 In order to solve the problem of aflatoxin B₁(AFB₁)contamination in feed and food, an AFB₁- degrading strain was screened from soil samples and its capacities for degradation of AFB₁ and inhibition of Aspergillus flavus growth were studied.【Method】 Using coumarin as the sole carbon source, an efficient AFB₁ degrading strain was selected. The species of the strain were identified by 16S rRNA gene sequencing and its degradation characteristics of AFB₁ were studied by High performance liquid chromatography(HPLC). The degradation efficiency of GDAAS003 on AFB₁ was optimized by single factor experiment, and the inhibition effect of GDAAS003 on A. flavus growth was analyzed by co-culture. Finally, the SOS-Chromotest was used to evaluate the detoxification of AFB₁ by the strain.【Result】Through HPLC detection, a highly efficient AFB₁-degrading strain was selected. 16S rRNA analysis showed that the sequence of GDAAS003 was 100% homologous to that of Streptomyces cerasinus SR3-134(LC128347.1), and that the AFB₁ degradation activity was extracellular and enzymatic. The results showed that the optimum pH of supernatants to degrade AFB₁ was 8.0 in Na₂HPO₄/NaH₂PO₄ buffer and that the optimum temperature was 30℃. Under the optimized condition, the degradation rate of 50 and 100 ng/mL AFB₁ in 96 h of strain supernatant was 90.50% and 75.68%, respectively. Moreover, the genotoxicity test results of the degradation products showed that the degradation products did not show genotoxicity. In addition, GDAAS003 could inhibit AFB₁ synthesis by A. flavus in maize.【Conclusion】Streptomyces GDAAS003 not only degraded AFB₁ with high efficiency, but also inhibited the growth of A. flavus. It has a great application prospect in the food and feed industries.