好氧、高葡萄糖消耗及快速生长条件下，细菌会将葡萄糖部分氧化生成乙酸，而非通过TCA循环充分氧化，该现象称为乙酸代谢溢流。乙酸代谢溢流可以平衡细菌能量合成及生物量合成所需蛋白量以支持快速生长，但乙酸积累会促进超氧化物产生，降低胞内pH，最终导致细菌死亡。研究者尝试通过敲除乙酸合成途径，激活TCA循环等多种手段抑制乙酸代谢溢流的发生，但均未取得理想效果。申请者前期研究发现阴沟肠杆菌快速生长过程中并不存在乙酸代谢溢流造成的负面影响，该菌株可能通过2,3-丁二醇（BD）合成与乙醇生成的协同作用实现乙酸代谢溢流的消除。本项目拟确定阴沟肠杆菌乙酸代谢溢流消除中乙酸的流向及乙醇生成的功能；揭示BD合成参与乙酸代谢溢流消除的具体作用；阐明BD合成与乙醇生成关键酶协同表达的调控机制；分析乙酸代谢溢流消除对阴沟肠杆菌的全局影响；为通过消除乙酸代谢溢流提高工业微生物的应用潜力提供理论依据。

During aerobic, high glucose consumption and rapid growth stage, the bacteria will partially oxidize glucose into acetate, not fully oxidize it through the TCA cycle. This phenomenon was known as acetate overflow. Acetate overflow can balance the proteins required for bacterial energy synthesis and biomass synthesis to support the rapid growth. However, the accumulation of acetate will promote superoxide generation, reduce intracellular pH, eventually lead to bacterial death. Researchers have tried many methods such as knocking out the acetate synthesis pathway, activating TCA cycle to inhibit the acetate overflow, but did not achieve the desired effect. In our previous study, we found that there is no negative effect caused by acetate overflow during the culture of Enterobacter cloacae SDM. Further studies showed that 2,3-butanediol (BD) synthesis might cooperate with alcohol production to eliminate the acetate overflow in strain SDM. In this project, we would use E. cloacae SDM as the research object for the study of the acetate overflow elimination mechanism. The project would determine the flow direction of acetate metabolic process and the function of alcohol production. Then, the specific mechanisms of BD synthesis pathway involved in the elimination of acetate overflow and the coordinated expression mechanism of key enzymes in BD biosynthesis and alcohol production would be clarified. Finally, the global influence of acetate overflow elimination in E. cloacae would be analyzed. The result of the project would lay the theoretical foundation to improve the application potential of industrial microorganisms by acetate overflow elimination.