Identification of a Bacillus amyloliquefaciens H6 Thioesterase Involved in Zearalenone Detoxification by Transcriptomic Analysis

Zearalenone (ZEA), a nonsteroidal estrogenic mycotoxin produced by Fusarium graminearum, induces hyperestrogenic responses in mammals and can cause reproductive disorders in farm animals. In this study, a transcriptome analysis of Bacillus amyloliquefaciens H6, which was previously identified as a ZEA-degrading bacterium, was conducted with high-throughput sequencing technology, and the differentially expressed genes were subjected to gene ontology (GO) and kyoto encyclopedia of genes and genomes (KEGG) enrichment analyses. Among the 16 upregulated genes, BAMF_RS30125 was predicted to be the key gene responsible for ZEA degradation. The protein encoded by BAMF_RS30125 was then expressed in Escherichia coli, and this recombinant protein (named ZTE138) significantly reduced the ZEA content, as determined by the enzyme-linked immunosorbent assay (ELISA) and high-performance liquid chromatography (HPLC), and decreased the proliferating activity of ZEA in MCF-7 cells. What is more, the liquid chromatography–tandem mass spectrometry (LC–MS/MS) results showed that the relative molecular mass and the structure of ZEA also changed. Sequence alignment of the ZTE138 protein showed that it is a protease that belongs to the YBGC/FADM family of coenzyme A thioesterases, and thus, the protein can presumably cleave the ZEA lactone bond and break down its macrolide ring.