Microbial electrosynthesis (MES) and other bioprocesses such as syngas fermentation developed for energy storage and the conversion of carbon dioxide into valuable chemicals often employs acetogens as microbial catalysts. Acetogens are sensitive to molecular oxygen, which means that bioproduction reactors must be maintained under strict anaerobic conditions. This requirement increases cost and does not eliminate the possibility of O₂ leakage. For MES, the risk is even greater since the system generates O₂ when water splitting is the anodic reaction. Here, we show that O₂ from the anode of a MES reactor diffuses into the cathode chamber where strict anaerobes reduce CO₂. To overcome this drawback, a stepwise adaptive laboratory evolution (ALE) strategy is used to develop the O₂ tolerance of the acetogen Sporomusa ovata. Two heavily-mutated S. ovata strains growing well autotrophically in the presence of 0.5 to 5% O₂ were obtained. The adapted strains were more performant in the MES system than the wild type converting electrical energy and CO₂ into acetate 1.5 fold faster. This study shows that the O₂ tolerance of acetogens can be increased, which leads to improvement of the performance and robustness of energy-storage bioprocesses such as MES where O₂ is an inhibitor.

微生物电合成（MES）和其他生物过程，例如为存储能量而开发的合成气发酵，以及将二氧化碳转化为有价值的化学物质，经常使用产乙酸原作为微生物催化剂。产乙酸激素对分子氧敏感，这意味着生物生产反应器必须保持在严格的厌氧条件下。该要求增加了成本，并且没有消除O ₂泄漏的可能性。对于MES，风险更大，因为当水分解是阳极反应时，系统会生成O ₂。在这里，我们表明来自MES反应器阳极的O ₂扩散到阴极室中，在那里严格的厌氧菌会减少CO ₂。为了克服此缺点，采用了逐步适应性实验室进化（ALE）策略来开发卵原产卵菌Sporomusa ovata的O ₂耐受性。获得了在0.5-5％O ₂的存在下自养生长良好的两个严重突变的卵形链球菌。与野生型将电能和CO ₂转化为乙酸盐的速度快了1.5倍相比，适应性菌株在MES系统中的性能更高。这项研究表明，可以提高对乙酸原的O ₂耐受性，从而改善能量存储生物过程（例如MES，其中O ₂是抑制剂）的性能和耐用性。