Han Yi-Fan, Xie Bin-Tao, Wu Guang-Xun, Guo Ya-Qiong, Li De-Mao, Huang Zhi-Yong
Tianjin Key Laboratory for Industrial Biological Systems and Bioprocessing Engineering, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China.
National Technology Innovation Center of Synthetic Biology, Tianjin, China.
Front Microbiol. 2020 Sep 25;11:577266. doi: 10.3389/fmicb.2020.577266. eCollection 2020.
Higher alcohols such as butanol (C4 alcohol) and hexanol (C6 alcohol) are superior biofuels compared to ethanol. P7 is a typical acetogen capable of producing C4 and C6 alcohols natively. In this study, the composition of trace metals in culture medium was adjusted, and the effects of these adjustments on artificial syngas fermentation by P7 were investigated. Nickel and ferrous ions were essential for growth and metabolite synthesis during syngas fermentation by P7. However, a decreased dose of molybdate improved alcohol fermentation performance by stimulating carbon fixation and solventogenesis. In response to the modified trace metal composition, cells grew to a maximum OD of 1.6 and accumulated ethanol and butanol to maximum concentrations of 2.0 and 1.0 g/L, respectively, in serum bottles. These yields were ten-fold higher than the yields generated using the original composition of trace metals. Furthermore, 0.5 g/L of hexanol was detected at the end of fermentation. The results from gene expression experiments examining genes related to carbon fixation and organic acid and solvent synthesis pathways revealed a dramatic up-regulation of the Wood-Ljungdahl pathway (WLP) gene cluster, the gene cluster, and a putative CoA transferase and butanol dehydrogenase, thereby indicating that both synthesis and acid re-assimilation contributed to the significantly elevated accumulation of higher alcohols. The gene was speculated to be the key target for butanol synthesis during solventogenesis.
与乙醇相比，丁醇（C4醇）和己醇（C6醇）等高级醇是更优质的生物燃料。P7是一种典型的产乙酸菌，能够天然产生C4和C6醇。在本研究中，调整了培养基中痕量金属的组成，并研究了这些调整对P7人工合成气发酵的影响。镍和亚铁离子对于P7在合成气发酵过程中的生长和代谢产物合成至关重要。然而，降低钼酸盐的剂量通过刺激碳固定和溶剂生成提高了酒精发酵性能。响应于痕量金属组成的改变，细胞在血清瓶中生长至最大OD值为1.6，乙醇和丁醇的积累浓度分别达到最大浓度2.0和1.0 g/L。这些产量比使用原始痕量金属组成产生的产量高十倍。此外，在发酵结束时检测到0.5 g/L的己醇。对与碳固定以及有机酸和溶剂合成途径相关的基因进行基因表达实验的结果显示，伍德-龙格达尔途径（WLP）基因簇、该基因簇以及一种假定的辅酶A转移酶和丁醇脱氢酶显著上调，从而表明合成和酸再同化都有助于高级醇积累的显著增加。推测该基因是溶剂生成过程中丁醇合成的关键靶点。
