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Electron availability in CO2 , CO and H2 mixtures constrains flux distribution, energy management and product formation in Clostridium ljungdahlii.
Microbial Biotechnology ( IF 4.8 ) Pub Date : 2020-07-21 , DOI: 10.1111/1751-7915.13625
Maria Hermann 1 , Attila Teleki 1 , Sandra Weitz 2 , Alexander Niess 1 , Andreas Freund 1 , Frank R Bengelsdorf 2 , Ralf Takors 1
Affiliation  

Acetogens such as Clostridium ljungdahlii can play a crucial role reducing the human CO2 footprint by converting industrial emissions containing CO2, CO and H2 into valuable products such as organic acids or alcohols. The quantitative understanding of cellular metabolism is a prerequisite to exploit the bacterial endowments and to fine‐tune the cells by applying metabolic engineering tools. Studying the three gas mixtures CO2 + H2, CO and CO + CO2 + H2 (syngas) by continuously gassed batch cultivation experiments and applying flux balance analysis, we identified CO as the preferred carbon and electron source for growth and producing alcohols. However, the total yield of moles of carbon (mol‐C) per electrons consumed was almost identical in all setups which underlines electron availability as the main factor influencing product formation. The Wood–Ljungdahl pathway (WLP) showed high flexibility by serving as the key NAD+ provider for CO2 + H2, whereas this function was strongly compensated by the transhydrogenase‐like Nfn complex when CO was metabolized. Availability of reduced ferredoxin (Fdred) can be considered as a key determinant of metabolic control. Oxidation of CO via carbon monoxide dehydrogenase (CODH) is the main route of Fdred formation when CO is used as substrate, whereas Fdred is mainly regenerated via the methyl branch of WLP and the Nfn complex utilizing CO2 + H2. Consequently, doubled growth rates, highest ATP formation rates and highest amounts of reduced products (ethanol, 2,3‐butanediol) were observed when CO was the sole carbon and electron source.

中文翻译:


CO2、CO 和 H2 混合物中的电子可用性限制了永大梭菌中的通量分布、能量管理和产物形成。



通过将含有CO 2 、CO和H 2的工业排放物转化为有机酸或醇等有价值的产品,诸如Clostridium ljungdahlii等产乙酸菌可以在减少人类CO 2足迹方面发挥关键作用。对细胞代谢的定量理解是利用细菌禀赋并通过应用代谢工程工具微调细胞的先决条件。通过连续通气分批培养实验并应用通量平衡分析,研究了三种气体混合物CO 2 + H 2 、CO和CO + CO 2 + H 2 (合成气),我们确定CO是生长和生产醇的首选碳源和电子源。然而,在所有设置中,每个消耗电子的碳摩尔数 (mol-C) 总产量几乎相同,这强调了电子可用性是影响产物形成的主要因素。 Wood-Ljungdahl 通路 (WLP) 作为 CO 2 + H 2的关键 NAD +提供者而表现出高度的灵活性,而当 CO 代谢时,这种功能受到转氢酶样 Nfn 复合物的强烈补偿。还原铁氧还蛋白(Fd red )的可用性可被视为代谢控制的关键决定因素。当CO作为底物时,CO通过一氧化碳脱氢酶(CODH)氧化是Fd形成的主要途径,而Fd主要通过WLP的甲基分支和利用CO 2 + H 2的Nfn复合物再生。 因此,当 CO 是唯一的碳源和电子源时,观察到加倍的生长速率、最高的 ATP 形成速率和最高量的还原产物(乙醇、2,3-丁二醇)。
更新日期:2020-07-21
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