Herzog Jan, Mook Alexander, Utesch Tyll, Bengelsdorf Frank R, Zeng An-Ping
Institute of Bioprocess and Biosystems Engineering, Hamburg University of Technology, Hamburg, Germany.
Institute of Molecular Biology and Biotechnology of Prokaryotes, Ulm University, Ulm, Germany.
Front Bioeng Biotechnol. 2023 Jun 23;11:1212044. doi: 10.3389/fbioe.2023.1212044. eCollection 2023.
Syngas fermentation processes with acetogens represent a promising process for the reduction of CO emissions alongside bulk chemical production. However, to fully realize this potential the thermodynamic limits of acetogens need to be considered when designing a fermentation process. An adjustable supply of H as electron donor plays a key role in autotrophic product formation. In this study an anaerobic laboratory scale continuously stirred tank reactor was equipped with an All-in-One electrode allowing for H generation via electrolysis. Furthermore, this system was coupled to online lactate measurements to control the co-culture of a recombinant lactate-producing strain and a lactate-consuming strain to produce caproate. When was grown in batch cultivations with lactate as substrate, 1.6 g·L caproate were produced. Furthermore, lactate production of the mutant strain could manually be stopped and reinitiated by controlling the electrolysis. Applying this automated process control, lactate production of the mutant strain could be halted to achieve a steady lactate concentration. In a co-culture experiment with the mutant strain and the strain, the automated process control was able to dynamically react to changing lactate concentrations and adjust H formation respectively. This study confirms the potential of as medium chain fatty acid producer in a lactate-mediated, autotrophic co-cultivation with an engineered strain. Moreover, the monitoring and control strategy presented in this study reinforces the case for autotrophically produced lactate as a transfer metabolite in defined co-cultivations for value-added chemical production.
产乙酸菌的合成气发酵过程是一种在减少二氧化碳排放以及大规模化学品生产方面颇具前景的工艺。然而，要充分实现这一潜力，在设计发酵工艺时需要考虑产乙酸菌的热力学极限。可调节的氢气作为电子供体的供应在自养产物形成中起着关键作用。在本研究中，一个厌氧实验室规模的连续搅拌罐反应器配备了一体化电极，可通过电解产生氢气。此外，该系统与在线乳酸测量相结合，以控制重组乳酸生产菌株和乳酸消耗菌株的共培养来生产己酸。当以乳酸为底物进行分批培养时，可产生1.6 g·L的己酸。此外，通过控制电解，可以手动停止和重新启动突变菌株的乳酸生产。应用这种自动过程控制，可以停止突变菌株的乳酸生产以实现稳定的乳酸浓度。在与突变菌株和菌株的共培养实验中，自动过程控制能够动态响应不断变化的乳酸浓度并相应地调整氢气生成。本研究证实了在与工程菌株进行乳酸介导的自养共培养中作为中链脂肪酸生产者的潜力。此外，本研究中提出的监测和控制策略强化了在特定共培养中自养产生的乳酸作为增值化学品生产的转移代谢物的情况。
