Feng Jiao, Lu Qiuhao, Li Kang, Xu Sheng, Wang Xin, Chen Kequan, Ouyang Pingkai
State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing, China.
Front Bioeng Biotechnol. 2020 Oct 15;8:590667. doi: 10.3389/fbioe.2020.590667. eCollection 2020.
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 PAO1 into . The engineered facilitated reduction of fumarate by using PCA as endogenous electron mediator driven by electricity. Furthermore, the heterologously expressed PCA pathway in 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 cells using heterologous self-excreted PCA as an electron transfer mediator in a bioelectrochemical system and lays a foundation for subsequent optimization.
微生物电合成（MES）或电发酵（EF）是一种很有前景的微生物电化学技术，可借助微生物细胞作为催化剂来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所处的发酵环境。电能的关键作用是为微生物代谢提供电子。为了实现电能的利用，一种称为内向型细胞外电子转移（EET）的过程是必要的，其效率对生物电化学系统至关重要。使用电子介体是实现电子转移并提高EET效率的主要方法之一。为了突破外源电子介体的一些局限性，我们将来自PAO1的吩嗪-1-羧酸（PCA）途径引入到[具体微生物名称未给出]中。经过工程改造的[具体微生物名称未给出]利用PCA作为由电驱动的内源性电子介体，促进了富马酸酯的还原。此外，在[具体微生物名称未给出]中异源表达的PCA途径导致了更好的EET效率和向更多还原代谢产物产生的强烈代谢转变，但系统中的生物量较低。然后，我们发现作为代谢中“能量货币”的三磷酸腺苷（ATP）的合成也受到了影响。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。本研究证明了在生物电化学系统中使用异源自分泌PCA作为电子转移介体在电极和[具体微生物名称未给出]细胞之间进行电子转移的可行性，并为后续优化奠定了基础。
