A novel experimental method to determine substrate uptake kinetics of gaseous substrates applied to the carbon monoxide-fermenting Clostridium autoethanogenum

Maximilienne T. Allaart, Charilaos Korkontzelos, Diana Z. Sousa, Robbert Kleerebezem*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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Abstract

Syngas fermentation has gained momentum over the last decades. The cost-efficient design of industrial-scale bioprocesses is highly dependent on quantitative microbial growth data. Kinetic and stoichiometric models for syngas-converting microbes exist, but accurate experimental validation of the derived parameters is lacking. Here, we describe a novel experimental approach for measuring substrate uptake kinetics of gas-fermenting microbes using the model microorganism Clostridium autoethanogenum. One-hour disturbances of a steady-state chemostat bioreactor with increased CO partial pressures (up to 1.2 bar) allowed for measurement of biomass-specific CO uptake- and CO2 production rates ((Formula presented.), (Formula presented.)) using off-gas analysis. At a pCO of 1.2 bar, a (Formula presented.) of −119 ± 1 mmol g−1X h−1 was measured. This value is 1.8–3.5-fold higher than previously reported experimental and kinetic modeling results for syngas fermenters. Analysis of the catabolic flux distribution reveals a metabolic shift towards ethanol production at the expense of acetate at pCO (Formula presented.) 0.6 atm, likely to be mediated by acetate availability and cellular redox state. We characterized this metabolic shift as acetogenic overflow metabolism. These results provide key mechanistic understanding of the factors steering the product spectrum of CO fermentation in C. autoethanogenum and emphasize the importance of dedicated experimental validation of kinetic parameters.

Original languageEnglish
Pages (from-to)1325-1335
Number of pages11
JournalBiotechnology and Bioengineering
Volume121
Issue number4
DOIs
Publication statusPublished - 2024

Keywords

  • acetogen
  • chemostat
  • metabolic shift
  • overflow metabolism
  • pulse feeding
  • syngas

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