Acetogenic bacteria (acetogens) are microorganisms with high potential as biocatalysts that can convert C1 gas, such as carbon dioxide (CO₂₎ or carbon monoxide (CO), into biomass or biochemicals; however, high CO concentrations cause growth retardation in these microorganisms. In this study, we performed adaptive evolution of Eubacterium limosum, an acetogen, for approximately 400 generations under high CO synthetic gas (syngas) conditions to obtain E. limosum ECO2, which can rapidly proliferate even under high CO conditions. A mutation was revealed in H636R in the Acetyl-CoA synthase (ACS) protein of the ECO2 strain through whole-genome re-sequencing, and the mutation increased the CO gas conversion rate. By analyzing the transcript profiling of the ECO2 strain under high CO syngas conditions, the transcript levels of the methyl branch in the Wood–Ljungdahl pathway and the energy conservation system increased at high CO concentration conditions. Finally, to convert CO into value-added biochemicals, 2,3-BDO (2,3-butanediol) biosynthesis pathways were constructed and transformed into the E. limosum ECO2 strain. This strain showed capability to produce 2.60 mg L^-1 h^-1 of 2,3-BDO through CO 66% syngas fed-batch fermentation. This was 4.6-fold higher than that of the wild type. We developed a microorganism with high CO tolerance, and this strain showed high application potential as a biocatalyst that can efficiently convert CO gas into value-added chemicals.

产乙酸菌（acetogens）是作为生物催化剂具有很高潜力的微生物，可以将二氧化碳（CO _{2 ）}或一氧化碳（CO）等C1气体转化为生物质或生化物质；然而，高 CO 浓度会导致这些微生物的生长迟缓。在这项研究中，我们在高 CO 合成气（合成气）条件下对Eubacterium limosum （一种产乙酸菌）进行了大约 400 代的适应性进化，以获得E. limosumECO2，即使在高 CO 条件下也能迅速增殖。通过全基因组重测序发现ECO2菌株乙酰辅酶A合酶（ACS）蛋白H636R发生突变，该突变增加了CO气体转化率。通过分析 ECO2 菌株在高 CO 合成气条件下的转录谱，Wood-Ljungdahl 途径和能量守恒系统中甲基分支的转录水平在高 CO 浓度条件下增加。最后，为了将 CO 转化为增值生化产品，构建了 2,3-BDO（2,3-丁二醇）生物合成途径并将其转化到E. limosum ECO2 菌株中。该菌株显示出产生 2.60 mg L ^-1 h ^-1的能力通过 CO 66% 合成气补料分批发酵生产 2,3-BDO。这比野生型高 4.6 倍。我们开发了一种具有高 CO 耐受性的微生物，该菌株作为一种生物催化剂具有很高的应用潜力，可以有效地将 CO 气体转化为增值化学品。