The stability of our planet is threatened by climate change, necessitating a shift towards a circular economy in the (bio-)chemical industry to sustainably meet our increasing product demand. Syngas fermentation by acetogenic bacteria, such as Clostridium autoethanogenum, has been identified as a sustainable alternative for the production of biofuels and other chemicals. These bacteria harbour the Wood-Ljungdahl pathway (WLP), enabling them to convert carbon monoxide (CO), carbon dioxide (CO₂) and hydrogen (H₂) into acetate and ethanol. Several process parameters influence the outcome of syngas fermentation and their effects on the metabolic behaviour of syngas fermenting bacteria can be quantified through kinetic modelling.

This study aimed to build a simple quantitative model for steady-state CO fermentation by C. autoethanogenum using unstructured microbial kinetics and the current insights into the ATP production of the CO pathways to acetate and ethanol. To this aim, a dataset compromising 37 steady-state lab-scale syngas fermentations was compiled. Incomplete data was reconciled and recovery gaps were addressed through data reconciliation applied to the dataset. Furthermore, the growth kinetics of C. autoethanogenum was described by coupling ATP production in the catabolism to energy requirements for growth and maintenance through a modified Herbert-Pirt equation. Finally, a preliminary model for CO fermentation by C. autoethanogenum was presented, which given the gas inflow rate, gas inflow composition and liquid dilution rate should predict the consumption and production rates. Moreover, this study emphasizes the necessity for methodologies to measure dissolved gas concentrations and highlights the research gap concerning gas uptake kinetics in syngas fermentation.
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