Online monitoring applying the anaerobic respiratory monitoring system reveals iron(II) limitation in YTF medium for Clostridium ljungdahlii

Abstract

Online monitoring of microbial cultures is an effective approach for studying both aerobic and anaerobic microorganisms. Especially in small‐scale cultivations, several parallel online monitored experiments can generate a detailed understanding of the cultivation, compared to a situation where a few data points are generated from time course sampling and offline analysis. However, the availability of small‐scale online monitoring devices for acetogenic organisms is limited. In this study, the previously reported anaerobic Respiration Activity MOnitoring System (anaRAMOS) device was adapted for online monitoring of Clostridium ljungdahlii (C. ljungdahlii) cultures with fructose as the carbon source. The anaRAMOS was applied to identify conversion of different carbon sources present in commonly used YTF medium. An iron(II) deficiency was discovered in this medium for C. ljungdahlii. Addition of iron(II) to the YTF medium reduced the cultivation time and increased biomass yield of C. ljungdahlii cultures by 50% and 40%, respectively. The measurement of the carbon dioxide transfer rate was used to calculated the iron(II) contained in complex components. By demonstrating the application of the anaRAMOS device for medium optimization, it is proven that the described online monitoring device has potential for use in process development.

Impact of different trace elements on metabolic routes during heterotrophic growth of C. ljungdahlii investigated through online measurement of the carbon dioxide transfer rate

“…Different studies investigated trace element composition and showed the inherent potential in fermentation optimization by adjusting the trace element composition 31,42,43 . YTF medium is a medium commonly employed for heterotrophic growth of C. ljungdahlii 36,45–49 . Since YTF (Yeast extract‐Tryptone‐Fructose) medium only contains the trace elements provided through yeast extract and tryptone, it is debatable whether all required trace elements for the maximum activity of the WLP are provided in this medium.…”

“…To study the impact of trace metals on metabolic activity, the anaerobic Respiration Activity Monitoring System (anaRAMOS) device was used. The anaRAMOS offers the possibility of real‐time online monitoring of the carbon dioxide transfer rate (CTR) in up to eight parallel shake flasks 49,50 . The measured CTR is a direct quantitative indication of metabolic activity and can be used to calculate the total amount of produced net CO 2 (CT).…”

“…The anaRAMOS has previously been demonstrated to be a helpful tool to optimize growth conditions 49 . Through this method an iron(II)‐deficiency in YTF medium for C. ljungdahlii was detected.…”

“…Through this method an iron(II)‐deficiency in YTF medium for C. ljungdahlii was detected. A model was introduced, which allows determination of the necessary amount of iron(II) for unlimited growth on a given amount of fructose 49 . In the present study, the addition of metal salts from PETC 1754 medium (iron, cobalt, manganese, zinc, nickel, copper, selenium, and tungsten) to YTF medium was analyzed to demonstrate the influence of different trace elements on the cultivation of C. ljungdahlii in complex medium.…”

Online monitoring of gas transfer rates during CO and CO/H2 gas fermentation in quasi‐continuously ventilated shake flasks

“…In anaerobic applications, CTR and the total gas transfer rate (TGTR) were used to identify diauxic growth, and to predict the hydrogen production by Clostridium pasteurianum (Munch et al, 2019). The anaRAMOS was also described as a potent tool for online monitoring of the cultivation of acetogenic Clostridia on dissolved solid substrates, such as fructose (Mann et al, 2020). Cultivation using a continuous supply of gaseous carbon and energy substrates has not been possible so far.…”