Department of Chemical, Materials and Production Engineering-Università degli Studi di Napoli Federico II, P.le V. Tecchio 80, 80125 Napoli, Italy.
Department of Chemical Engineering, University of Valencia, Burjassot 46100, Spain.
N Biotechnol. 2024 Jul 25;81:1-9. doi: 10.1016/j.nbt.2024.02.004. Epub 2024 Feb 22.
Leveraging renewable carbon-based resources for energy and chemical production is a promising approach to decrease reliance on fossil fuels. This entails a thermo/biotechnological procedure wherein bacteria, notably Clostridia, ferment syngas, converting CO or CO + H into Hexanol, Butanol and Ethanol (H-B-E fermentation). This work reports of Clostridium carboxidivorans performance in a stirred tank reactor continuously operated with respect to the gas and the cell/liquid phases. The primary objective was to assess acid and solvent production at pH 5.6 by feeding pure CO or synthetic syngas under gas flow differential conditions. Fermentation tests were conducted at four different dilution rates (D) of the fresh medium in the range 0.034-0.25 h. The fermentation pathways of C. carboxidivorans were found to be nearly identical for both CO and syngas, with consistent growth and metabolite production at pH 5.6 within a range of dilution rates. Wash-out conditions were observed at a D of 0.25 h regardless of the carbon source. Ethanol was the predominant solvent produced, but a shift towards butanol production was observed with CO as the substrate and towards hexanol production with synthetic syngas. In particular, the maximum cell concentration (0.5 g/L) was obtained with pure CO at D 0.05 h; the highest solvent productivity (60 mg/L*h of total solvent) was obtained at D 0.17 h by using synthetic syngas as C-source. The findings highlight the importance of substrate composition and operating conditions in syngas fermentation processes. These insights contribute to the optimization of syngas fermentation processes for biofuel and chemical production.
利用可再生碳基资源进行能源和化学生产是减少对化石燃料依赖的一种很有前途的方法。这需要一个热/生物技术过程，其中细菌，特别是梭菌，发酵合成气，将 CO 或 CO+H 转化为己醇、丁醇和乙醇（H-B-E 发酵）。本工作报道了连续操作的搅拌罐反应器中羧化梭菌的性能，涉及气相与细胞/液相。主要目标是在 pH 5.6 下评估纯 CO 或合成合成气进料时的酸和溶剂生成，在气体流量差条件下进行发酵试验。在新鲜培养基的四个不同稀释率（D）下进行发酵试验，范围为 0.034-0.25 h。发现 CO 和合成气的发酵途径几乎相同，在 pH 5.6 范围内的稀释率范围内具有一致的生长和代谢产物生成。无论碳源如何，在 D 0.25 h 时观察到洗出条件。乙醇是主要的溶剂产物，但观察到随着 CO 作为底物，向丁醇生产的转变，以及随着合成合成气，向己醇生产的转变。特别是，在 D 0.05 h 时用纯 CO 获得了最高的细胞浓度（0.5 g/L）；在 D 0.17 h 时用合成合成气作为 C 源获得了最高的溶剂生产率（60 mg/L*h 的总溶剂）。研究结果强调了底物组成和操作条件在合成气发酵过程中的重要性。这些见解有助于优化生物燃料和化学合成气发酵过程。
