Metabolomic insights into the role of isoleucine in regulating Cereulide biosynthesis in emetic Bacillus cereus

Bacillus cereus is a significant cause of foodborne illnesses, particularly through starchy foods like rice and pasta, leading to the vomiting symptom. The primary toxin involved, cereulide, is preformed within contaminated food and exhibits high resistance to heat, making it particularly difficult to control. Since cereulide persists even after standard food processing methods, its prevention and control remain critical for the food industry. Isoleucine (Ile), a branched-chain amino acid (BCAA), has been linked to the regulation of cereulide production, but the exact mechanisms remain unclear. Based on untargeted metabolomics analysis using liquid chromatography-mass spectrometry (LC-MS), this study demonstrated that Ile supplementation markedly downregulated the folate biosynthesis pathway in B. cereus . Supplementation with folic acid partially restored cereulide production that had been suppressed by Ile. In addition, RT-qPCR analysis revealed significant changes in the expression of key enzymes involved in folate metabolism and related pathways following Ile exposure, further supporting the notion that Ile inhibits cereulide synthesis by disruption of folate metabolism. Collectively, these findings suggest a novel mechanism by which Ile regulates cereulide production via folate metabolism, providing new insights for the effective prevention and control of cereulide production in B. cereus .