玉米赤霉烯酮（ZEN）对人和动物具有生殖发育毒性、致癌性、免疫毒性以及肝肾毒性。利用微生物对ZEN降解条件和降解效率的研究很多，但是对其详细的降解途径和降解机制的研究未见报道。本项目前期分离到两株ZEN降解效率差异显著的芽孢杆菌SCK6和ZSH06，并且建立了枯草芽孢杆菌SCK6的遗传操作体系和基因编辑方法。本项目拟以SCK6为研究对象，通过全基因组扫描初步推测ZEN生物降解途径和关键基因，通过单基因敲除鉴定苯环开环关键基因，利用单基因突变体文库构建与筛选鉴定其他降解关键酶，再利用回补结合体外表达和生化手段探究降解关键酶的催化功能，进而从分子水平上揭示ZEN生物降解机制，重构ZEN生物降解途径，并通过比较基因组学对高效降解菌株ZSH06的降解机制进行推测，初步研究ZEN生物降解的调控机制。为ZEN生物降解的广泛应用和多种真菌毒素降解菌株的构建奠定基础。

Zearalenone (ZEN) has reproductive toxicity, carcinogenicity, immunotoxicity and hepatorenal toxicity to humans and animals. Compared to the extensive studies on the degradation conditions and efficiency of ZEN in microorganisms, the understanding on its degradation pathway and mechanism have not been reported. In our preliminary studies, two Bacillus strains, Bacillus subtilis SCK6 and Bacillus velezensis ZSH06, were isolated with different ZEN degradation efficiency, and the genetic manipulation and gene editing methods of SCK6 were established. In this project, Bacillus subtilis SCK6 will be used as a study object to reveal a novel ZEN biodegradation mechanism in molecular level. Firstly, the key genes related to ZEN biodegradation will be identified through the genome-wide scanning of Bacillus subtilis SCK6. Subsequently, the functional roles of these genes will be confirmed using CRISPR/Cas9 gene editing tools and genetic methods. Followed by enzyme purification and biochemical analysis, the catalytic functions of key enzymes in the ZEN degradation pathway will be characterized. In addition, we will attempt to interpret the ZEN degradation mechanism in Bacillus velezensis ZSH06 through it genome comparison to Bacillus subtilis SCK6, which will prompt our understanding of the regulatory mechanisms in these two Bacillus strains. Our studies will lay a foundation for the wide application of ZEN biodegradation and construction of various mycotoxin-degrading strains.