Microbial biosynthesis of hydrocarbon from CO₂ reduction driven by electron uptake process from the cathodic electrode has gained intensive attention in terms of potential industrial application. However, a lack of a model system for detailed studies on the mechanism of the CO₂ reduction hinders the improvement in efficiency for microbial electrosynthesis. Here, we examined the mechanism of microbial CO₂ reduction at the cathode by a well‐described microbe for extracellular electron uptake, Shewanella oneidensis MR‐1, capable of reducing gaseous CO₂ to produce formic acid. Using whole‐cell electrochemical assay, we observed stable cathodic current production at −0.65 V vs Ag/AgCl KCl sat. associated with the introduction of CO₂. The observed cathodic current was enhanced by the addition of 4 μM riboflavin, which specifically accelerates the electron uptake process of MR‐1 by the interaction to its outer‐membrane c‐type cytochromes. The significant impact of an uncoupler agent and a mutant strain of MR‐1 lacking sole F‐type ATPase suggested the importance of proton import to the cytoplasm for the cathodic CO₂ reduction. The present data suggest that MR‐1 potentially serves as a model system for microbial electrosynthesis from CO₂.

中文翻译：

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质子转移参与二氧化碳还原反应与胞外电子吸收在Shewanella oneidensis MR-1中的关系

在潜在的工业应用方面，由阴极电极的电子吸收过程驱动的由CO ₂还原产生的微生物生物合成碳得到了广泛的关注。然而，缺乏用于详细研究CO ₂还原机理的模型系统阻碍了微生物电合成效率的提高。在这里，我们研究了阴极上微生物CO ₂还原的机理，该微生物被描述得很好的细胞外电子吸收能力，即Shewanella oneidensis MR-1，能够还原气态CO ₂产生甲酸。使用全电池电化学分析，我们观察到在相对于Ag / AgCl KCl饱和溶液-0.65 V时稳定的阴极电流产生。与引入CO _2有关。加入4μM核黄素可增强所观察到的阴极电流，该核黄素通过与MR-1的外膜c型细胞色素相互作用而特别加速了MR-1的电子吸收过程。缺乏唯一F型ATPase的解偶联剂和MR-1突变株的重大影响表明，质子输入到细胞质中对于减少阴极CO ₂的重要性。目前的数据表明，MR-1可能作为CO ₂微生物电合成的模型系统。