Screening a Strain of Aspergillus niger and Optimization of Fermentation Conditions for Degradation of Aflatoxin B1

Aflatoxin B1, a type of highly toxic mycotoxin produced by some species belonging to theAspergillusgenus, such asAspergillus flavusandAspergillus parasiticus, is widely distributed in feed matrices. Here, coumarin was used as the sole carbon source to screen microorganism strains that were isolated from types of feed ingredients. Only one isolate (ND-1) was able to degrade aflatoxin B1after screening. ND-1 isolate, identified as a strain ofAspergillus nigerusing phylogenetic analysis on the basis of 18S rDNA, could remove 26.3% of aflatoxin B1after 48 h of fermentation in nutrient broth (NB). Optimization of fermentation conditions for aflatoxin B1degradation by selectedAspergillus nigerwas also performed. These results showed that 58.2% of aflatoxin B1was degraded after 24 h of culture under the optimal fermentation conditions. The aflatoxin B1degradation activity ofAspergillus nigersupernatant was significantly stronger than cells and cell extracts. Furthermore, effects of temperature, heat treatment, pH, and metal ions on aflatoxin B1degradation by the supernatant were examined. Results indicated that aflatoxin B1degradation ofAspergillus nigeris enzymatic and this process occurs in the extracellular environment.Keywords:Aspergillus niger;coumarin;aflatoxin B1;degradation