Zhang Junqi, Chen Zheng, Liu Changjiang, Li Jianxun, An Xingjuan, Wu Deguang, Sun Xi, Zhang Baocai, Fu Longping, Li Feng, Song Hao
Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin, China.
Collaborative Innovation Center of Chemical Science and Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin, China.
Front Bioeng Biotechnol. 2021 Nov 19;9:757953. doi: 10.3389/fbioe.2021.757953. eCollection 2021.
Microbial fuel cells (MFCs) are a novel bioelectrochemical devices that can use exoelectrogens as biocatalyst to convert various organic wastes into electricity. Among them, acetate, a major component of industrial biological wastewater and by-product of lignocellulose degradation, could release eight electrons per mole when completely degraded into CO and HO, which has been identified as a promising carbon source and electron donor. However, MR-1, a famous facultative anaerobic exoelectrogens, only preferentially uses lactate as carbon source and electron donor and could hardly metabolize acetate in MFCs, which greatly limited Coulombic efficiency of MFCs and the capacity of bio-catalysis. Here, to enable acetate as the sole carbon source and electron donor for electricity production in , we successfully constructed three engineered (named AceU1, AceU2, and AceU3) by assembling the succinyl-CoA:acetate CoA-transferase (SCACT) metabolism pathways, including acetate coenzyme A transferase encoded by and gene from and citrate synthase encoded by the gene from , which could successfully utilize acetate as carbon source under anaerobic and aerobic conditions. Then, biochemical characterizations showed the engineered strain AceU3 generated a maximum power density of 8.3 ± 1.2 mW/m with acetate as the sole electron donor in MFCs. In addition, when further using lactate as the electron donor, the maximum power density obtained by AceU3 was 51.1 ± 3.1 mW/m, which approximately 2.4-fold higher than that of wild type (WT). Besides, the Coulombic efficiency of AceU3 strain could reach 12.4% increased by 2.0-fold compared that of WT, which demonstrated that the engineered strain AceU3 can further utilize acetate as an electron donor to continuously generate electricity. In the present study, we first rationally designed for enhancing the electron generation by using acetate as sole carbon source and electron donor. Based on synthetic biology strategies, modular assembly of acetate metabolic pathways could be further extended to other exoelectrogens to improve the Coulombic efficiency and broaden the spectrum of available carbon sources in MFCs for bioelectricity production.
微生物燃料电池（MFCs）是一种新型生物电化学装置，它可以利用产电微生物作为生物催化剂，将各种有机废物转化为电能。其中，乙酸盐是工业生物废水的主要成分和木质纤维素降解的副产物，每摩尔完全降解为二氧化碳和水时可释放8个电子，已被确定为一种有前景的碳源和电子供体。然而，著名的兼性厌氧产电微生物MR-1仅优先利用乳酸盐作为碳源和电子供体，在MFCs中几乎不能代谢乙酸盐，这极大地限制了MFCs的库仑效率和生物催化能力。在此，为了使乙酸盐作为唯一碳源和电子供体用于产电，我们通过组装琥珀酰辅酶A：乙酸辅酶A转移酶（SCACT）代谢途径，成功构建了三株工程菌（命名为AceU1、AceU2和AceU3），该代谢途径包括来自[具体物种1]的[具体基因1]和[具体基因2]编码的乙酸辅酶A转移酶以及来自[具体物种2]的[具体基因3]编码的柠檬酸合酶，它们能够在厌氧和好氧条件下成功利用乙酸盐作为碳源。然后，生化特性表明工程菌株AceU3在MFCs中以乙酸盐作为唯一电子供体时产生的最大功率密度为8.3±1.2 mW/m²。此外，当进一步使用乳酸盐作为电子供体时，AceU3获得的最大功率密度为51.1±3.1 mW/m²，约比野生型（WT）高2.4倍。此外，AceU3菌株的库仑效率可达12.4%，比WT提高了2.0倍，这表明工程菌株AceU3可以进一步利用乙酸盐作为电子供体持续产电。在本研究中，我们首次合理设计工程菌以增强利用乙酸盐作为唯一碳源和电子供体的电子生成。基于合成生物学策略，乙酸盐代谢途径的模块化组装可以进一步扩展到其他产电微生物，以提高库仑效率并拓宽MFCs中用于生物电生产的可用碳源谱。
