Rational design and modification of autotrophic bacteria to efficiently produce high-value chemicals and biofuels are crucial for establishing a sustainable and economically viable process for one-carbon (C1) source utilization, which, however, remains a challenge in metabolic engineering. In this study, autotrophic Clostridium ljungdahlii was metabolically engineered to efficiently co-produce three important bulk chemicals, isopropanol, 3-hydroxybutyrate (3-HB), and ethanol (together, IHE), using syngas (CO₂/CO). An artificial isopropanol-producing pathway was first constructed and optimized in C. ljungdahlii to achieve an efficient production of isopropanol and an unexpected product, 3-HB. Based on this finding, an endogenous active dehydrogenase capable of converting acetoacetate to 3-HB was identified in C. ljungdahlii, thereby revealing an efficient 3-HB-producing pathway. The engineered strain was further optimized to reassimilate acetic acid and synthesize 3-HB by introducing heterologous functional genes. Finally, the best-performing strain was able to produce 13.4, 3.0, and 28.4 g/L of isopropanol, 3-HB, and ethanol, respectively, in continuous gas fermentation. Therefore, this work represents remarkable progress in microbial production of bulk chemicals using C1 gases.

中文翻译：

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用于高效联产异丙醇、3-羟基丁酸和乙醇的气体发酵杨氏梭菌代谢工程

合理设计和修饰自养细菌以有效生产高价值化学品和生物燃料对于建立可持续且经济可行的单碳（C1）源利用过程至关重要，然而，这仍然是代谢工程的挑战。在这项研究中，自养型杨氏梭菌经过代谢工程改造，可使用合成气 (CO ₂ /CO)有效地共同生产三种重要的大宗化学品异丙醇、3-羟基丁酸酯 (3-HB) 和乙醇（统称为 IHE ）。首次构建并优化了杨氏假单胞菌的人工异丙醇生产途径实现异丙醇和意想不到的产品 3-HB 的高效生产。基于这一发现，在永氏梭菌中鉴定出一种能够将乙酰乙酸转化为 3-HB 的内源活性脱氢酶，从而揭示了一种有效的 3-HB 生产途径。通过引入异源功能基因，进一步优化工程菌株以重新同化乙酸并合成 3-HB。最后，表现最好的菌株能够在连续气体发酵中分别产生 13.4、3.0 和 28.4 g/L 的异丙醇、3-HB 和乙醇。因此，这项工作代表了使用 C1 气体微生物生产大宗化学品的显着进展。