Exploration of biodegradation mechanism by AFB1-degrading strain Aspergillus niger FS10 and its metabolic feedback

Significant progress has been made in the biological degradation of aflatoxin B1 (AFB1), which is the most toxic and carcinogenic mycotoxin commonly found in food and feed products; however, research in this area has currently focused on the effective methods for detoxifying AFB1 and the mechanisms underlying the degradation process. The relationship between AFB1 biotransformation and the metabolic feedback by the AFB1-degrading strain has rarely been reported. This study investigated the biotransformation pathway of AFB1 in a highly efficient degrading strain, Aspergillus niger FS10, and the metabolic regulation of FS10 during AFB1 degradation. We analyzed the AFB1 metabolic degradation products and evaluated its toxicity based on its structures by triple quadrupole-linear ion trap-mass spectrometry (Q-Trap-MS) coupled with LightSight™ Software. Four metabolic degradation products were obtained: Product 1 (C17H14O6), Product 2 (C17H14O7), Product 3 (C16H12O5), and Product 4 (C27H31N3O13, AFB2-GOH). Two biotransformation pathways were proposed based on the structures of these degradation products. Metabolomics data revealed that FS10 exhibited different degrees of bioremediation under low-, medium- and high- dose AFB1. The results also suggested the significant involvement of glutathione, a metabolite, in the AFB1 biotransformation pathway and its formation of AFB2-GOH with AFB1. The four products could probably be less toxic than AFB1, as reflected by changes in the AFB1 toxicity site. Therefore, the AFB1-degrading strain FS10 exhibits great potential for application in the detoxification of AFB1 in food and feed products.