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

Aflatoxin B-1, a type of highly toxic mycotoxin produced by some species belonging to the Aspergillus genus, such as Aspergillus flavus and Aspergillus 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 B-1 after screening. ND-1 isolate, identified as a strain of Aspergillus niger using phylogenetic analysis on the basis of 18S rDNA, could remove 26.3% of aflatoxin B-1 after 48 h of fermentation in nutrient broth (NB). Optimization of fermentation conditions for aflatoxin B-1 degradation by selected Aspergillus niger was also performed. These results showed that 58.2% of aflatoxin B-1 was degraded after 24 h of culture under the optimal fermentation conditions. The aflatoxin B-1 degradation activity of Aspergillus niger supernatant was significantly stronger than cells and cell extracts. Furthermore, effects of temperature, heat treatment, pH, and metal ions on aflatoxin B-1 degradation by the supernatant were examined. Results indicated that aflatoxin B-1 degradation of Aspergillus niger is enzymatic and this process occurs in the extracellular environment.