Kaspar Valgepea1, Renato d.S.P. Lemgruber1, Kim Q. Loi1, Kieran Meaghan1, Robin W. Palfreyman1, Tanus Abdalla2, Björn Heijstra2, James B. Behrendorff2, Ryan Tappel2, Michael Köpke2, Séan D. Simpson2, Lars K. Nielsen1 and Esteban Marcellin1,*


1Australian Institute for Bioengineering and Nanotechnology (AIBN), The University of Queensland, St. Lucia, QLD, Australia; 2LanzaTech Inc., Skokie, IL, USA


Gas fermentation has become a promising process for the renewable production of fuels and chemicals from inexpensive gaseous waste feedstocks (e.g. syngas, steel mill off-gas, methane). One instance uses gas-fermenting microorganisms termed acetogens to convert carbon dioxide (CO2) and carbon monoxide (CO) into valuable metabolic products. Due to the challenges with cultivating these stringent anaerobes, their physiology has not been exhaustively studied. Specifically, a systems biology approach is needed to accelerate their metabolic engineering. Thus we aimed to characterise and engineer acetogen metabolism using multi-omics fermentation data and a genome-scale metabolic model.

 We first used the metabolic model to find alternative energy-generating metabolic pathways in Clostridium autoethanogenum. Model-predicted cellular preferences for amino acids were experimentally confirmed and revealed that supply of arginine significantly increases energy production. This resulted in faster growth and near-abolishment of acetate excretion, a hallmark of acetogen metabolism. Next, we performed a systems-level study using metabolomics, transcriptomics, and proteomics analyses for Clostridium autoethanogenum steady-state cultures grown on CO, syngas (CO, CO2, H2), or a low CO/high H2 gasmix. Strikingly different carbon distributions were observed: increasing supply of additional reducing power in the form of H2 enabled the cells to ferment more CO into ethanol and waste less as CO2. Metabolic modelling accurately predicted growth phenotypes for H2-containing gasmixes and provided an answer to one of the remaining open questions about energy conservation in acetogens. Results from –omics analyses will also be presented during the talk.

Our work provides a reference dataset to advance the understanding and engineering of arguably the first carbon fixation pathway on Earth. The data potentially benefits gas fermentation as a bioprocess by describing an alternative route for supplying cells with energy and the effects of gas feed composition on cell growth.




Biographic Details

Name: Kaspar Valgepea        

Title: Dr.

Affiliation, Country: AIBN, UQ, Australia

E-mail: k.valgepea@uq.edu.au

Research interests: systems biology, metabolic engineering, metabolic modelling