Mann Marcel, Miebach Katharina, Büchs Jochen
AVT, Biochemical Engineering, RWTH Aachen University, Aachen, Germany.
Biotechnol Bioeng. 2021 Jan;118(1):253-264. doi: 10.1002/bit.27567. Epub 2020 Oct 1.
Syngas fermentation is one possible contributor to the reduction of greenhouse gas emissions. The conversion of industrial waste gas streams containing CO or H , which are usually combusted, directly reduces the emission of CO into the atmosphere. Additionally, other carbon-containing waste streams can be gasified, making them accessible for microbial conversion into platform chemicals. However, there is still a lack of detailed process understanding, as online monitoring of dissolved gas concentrations is currently not possible. Several studies have demonstrated growth inhibition of Clostridium ljungdahlii at high CO concentrations in the headspace. However, growth is not inhibited by the CO concentration in the headspace, but by the dissolved carbon monoxide tension (DCOT). The DCOT depends on the CO concentration in the headspace, CO transfer rate, and biomass concentration. Hence, the measurement of the DCOT is a superior method to investigate the toxic effects of CO on microbial fermentation. Since CO is a component of syngas, a detailed understanding is crucial. In this study, a newly developed measurement setup is presented that allows sterile online measurement of the DCOT. In an abiotic experiment, the functionality of the measurement principle was demonstrated for various CO concentrations in the gas supply (0%-40%) and various agitation rates (300-1100 min ). In continuous stirred tank reactor fermentation experiments, the measurement showed reliable results. The production of ethanol and 2,3-butanediol increased with increasing DCOT. Moreover, a critical DCOT was identified, leading to the inhibition of the culture. Thus, the reported online measurement method is beneficial for process understanding. In future processes, it can be used for closed-loop fermentation control.
合成气发酵是减少温室气体排放的一种可能途径。通常被燃烧的含一氧化碳或氢气的工业废气流的转化，直接减少了一氧化碳向大气中的排放。此外，其他含碳废物流可以被气化，使其能够通过微生物转化为平台化学品。然而，目前仍缺乏对详细过程的了解，因为目前无法在线监测溶解气体浓度。多项研究表明，在顶空高浓度一氧化碳条件下，Ljungdahlii梭菌的生长受到抑制。然而，生长并非受顶空一氧化碳浓度的抑制，而是受溶解一氧化碳分压（DCOT）的抑制。DCOT取决于顶空一氧化碳浓度、一氧化碳传质速率和生物量浓度。因此，测量DCOT是研究一氧化碳对微生物发酵毒性作用的一种更优方法。由于一氧化碳是合成气的一种成分，详细了解至关重要。在本研究中，提出了一种新开发的测量装置，可实现对DCOT的无菌在线测量。在非生物实验中，针对气体供应中不同的一氧化碳浓度（0%-40%）和不同的搅拌速率（300-1100分钟），验证了测量原理的功能。在连续搅拌釜式反应器发酵实验中，测量结果可靠。乙醇和2,3-丁二醇的产量随DCOT的增加而增加。此外，还确定了一个临界DCOT，导致培养物受到抑制。因此，所报道的在线测量方法有助于理解过程。在未来的工艺中，它可用于闭环发酵控制。
