Bioethanol production from syngas using acetogenic bacteria has attracted considerable attention in recent years. However, low ethanol yield is the biggest challenge that prevents the commercialization of syngas fermentation into biofuels using microbial catalysts. The present study demonstrated that ethanol metabolism plays an important role in recycling NADH/NAD⁺ during autotrophic growth. Deletion of bifunctional aldehyde/alcohol dehydrogenase (adhE) genes leads to significant growth deficiencies in gas fermentation. Using specific fermentation technology in which the gas pressure and pH were constantly controlled at 0.1 MPa and 6.0, respectively, we revealed that ethanol was formed during the exponential phase, closely accompanied by biomass production. Then, ethanol was oxidized to acetate via the aldehyde ferredoxin oxidoreductase pathway in Clostridium ljungdahlii. A metabolic experiment using ¹³C-labeled ethanol and acetate, redox balance analysis, and comparative transcriptomic analysis demonstrated that ethanol production and reuse shared the metabolic pathway but occurred at different growth phases.

中文翻译：

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一氧化碳生长的钟氏梭菌中乙醇的代谢动力学。

近年来，使用产乙酸细菌从合成气生产生物乙醇备受关注。然而，低乙醇收率是阻止使用微生物催化剂将合成气发酵商业化为生物燃料的最大挑战。本研究表明乙醇代谢在自养生长过程中在回收NADH / NAD ⁺中起着重要作用。删除双功能醛/醇脱氢酶（adhE）基因导致气体发酵中明显的生长缺陷。使用特定的发酵技术，将气压和pH分别恒定控制在0.1 MPa和6.0，我们发现在指数期形成了乙醇，并伴随着生物量的产生。然后，乙醇通过仲达氏梭菌中的醛铁氧还蛋白氧化还原酶途径被氧化成乙酸盐。使用¹³ C标记的乙醇和乙酸盐进行的代谢实验，氧化还原平衡分析和比较转录组分析表明，乙醇的生产和再利用共享代谢途径，但发生在不同的生长阶段。