A Strain Capable of Reducing Aflatoxin B₁: Identification, Optimization of Removal Conditions and Transcriptomic Analysis of Degradation Pathways

In this study, a strain of Wickerhamiella versatilis capable of degrading aflatoxin B₁ (AFB₁) was obtained. The removal conditions of AFB₁ by this strain were optimized and important physiological and metabolic processes were elucidated using transcriptomics. The results single factor experiments indicated that pH, temperature, and inoculum size had the most significant influence on the degradation rate of AFB₁. Using response surface methodology (RSM), the optimal fermentation conditions that provided maximum AFB₁ removal rate of 96.01% were obtained as follows: pH 5.6, 30 ℃, and inoculum size of 10%. Transcriptomic results revealed that 525 genes were differentially expressed under the stress of AFB₁, including 397 up-regulated and 128 down-regulated ones. Gene annotation was particularly notable in carbon metabolism and the phosphatidylinositol-3-kinase-protein kinase B (PI3K/Akt) signal pathway. Among these genes, the genes coding for lipoxygenase (LOX2S), glutathione S-transferase (GST), adenosylhomocysteinase (AHCY), aromatic amino acid aminotransferase I (ARO8), S-adenosylmethionine decarboxylase (speD) promoted the formation of AFB₁-exo-8,9-epoxide-glutathione (AFBO-GSH) conjugates, disrupted the double bond of the furan ring of AFB₁, and reduced its toxicity. Moreover, mass spectrometric analysis showed that in the presence of AFB₁, the GSH synthesis process of this strain was accelerated, and a large amount of the intermediate substance acetyl homoserine was generated. In summary, this study has practical significance for future research on intracellular removal of AFB₁.