Microbial electrosynthesis (MES) or electro-fermentation (EF) is a promising microbial electrochemical technology for the synthesis of valuable chemicals or high-value fuels with aid of microbial cells as catalysts. By introducing electrical energy (current), fermentation environments can be altered or controlled in which the microbial cells are affected. The key role for electrical energy is to supply electrons to microbial metabolism. To realize electricity utility, a process termed inward extracellular electron transfer (EET) is necessary, and its efficiency is crucial to bioelectrochemical systems. The use of electron mediators was one of the main ways to realize electron transfer and improve EET efficiency. To break through some limitation of exogenous electron mediators, we introduced the phenazine-1-carboxylic acid (PCA) pathway from Pseudomonas aeruginosa PAO1 into Escherichia coli. The engineered E. coli facilitated reduction of fumarate by using PCA as endogenous electron mediator driven by electricity. Furthermore, the heterologously expressed PCA pathway in E. coli led to better EET efficiency and a strong metabolic shift to greater production of reduced metabolites, but lower biomass in the system. Then, we found that synthesis of adenosine triphosphate (ATP), as the “energy currency” in metabolism, was also affected. The reduction of menaquinon was demonstrated as one of the key reactions in self-excreted PCA-mediated succinate electrosynthesis. This study demonstrates the feasibility of electron transfer between the electrode and E. coli cells using heterologous self-excreted PCA as an electron transfer mediator in a bioelectrochemical system and lays a foundation for subsequent optimization.

中文翻译：

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大肠杆菌生物电合成电子转移介质通路的构建

微生物电合成 (MES) 或电发酵 (EF) 是一种很有前途的微生物电化学技术，用于在微生物细胞作为催化剂的帮助下合成有价值的化学品或高价值燃料。通过引入电能（电流），可以改变或控制微生物细胞受到影响的发酵环境。电能的关键作用是为微生物代谢提供电子。为了实现电力效用，必须有一个称为细胞内细胞外电子转移 (EET) 的过程，其效率对生物电化学系统至关重要。电子介体的使用是实现电子转移和提高EET效率的主要途径之一。为了突破外源电子介体的一些限制，我们将来自铜绿假单胞菌 PAO1 的吩嗪-1-羧酸 (PCA) 途径引入大肠杆菌。工程大肠杆菌通过使用 PCA 作为由电驱动的内源电子介质来促进富马酸盐的还原。此外，大肠杆菌中异源表达的 PCA 途径导致更好的 EET 效率和强烈的代谢转变，以产生更多的还原代谢物，但系统中的生物量较低。然后，我们发现作为新陈代谢“能量货币”的三磷酸腺苷 (ATP) 的合成也受到影响。甲基萘醌的还原被证明是自分泌 PCA 介导的琥珀酸电合成中的关键反应之一。该研究证明了电极和 E 之间电子转移的可行性。