H 2 drives metabolic rearrangements in gas-fermenting Clostridium autoethanogenum .

Autor: Valgepea K; 1Australian Institute for Bioengineering and Nanotechnology (AIBN), The University of Queensland, St. Lucia, Australia., de Souza Pinto Lemgruber R; 1Australian Institute for Bioengineering and Nanotechnology (AIBN), The University of Queensland, St. Lucia, Australia., Abdalla T; LanzaTech Inc., Skokie, USA., Binos S; 3Thermo Fisher Scientific, Bio21 Institute, The University of Melbourne, Parkville, Australia., Takemori N; 4Proteo-Science Center, Ehime University, Ehime, Japan.; 5Advanced Research Support Center, Ehime University, Ehime, Japan., Takemori A; 4Proteo-Science Center, Ehime University, Ehime, Japan., Tanaka Y; 5Advanced Research Support Center, Ehime University, Ehime, Japan., Tappel R; LanzaTech Inc., Skokie, USA., Köpke M; LanzaTech Inc., Skokie, USA., Simpson SD; LanzaTech Inc., Skokie, USA., Nielsen LK; 1Australian Institute for Bioengineering and Nanotechnology (AIBN), The University of Queensland, St. Lucia, Australia., Marcellin E; 1Australian Institute for Bioengineering and Nanotechnology (AIBN), The University of Queensland, St. Lucia, Australia.; 6Queensland Node of Metabolomics Australia, The University of Queensland, St. Lucia, Australia.
Jazyk: angličtina
Zdroj: Biotechnology for biofuels [Biotechnol Biofuels] 2018 Mar 01; Vol. 11, pp. 55. Date of Electronic Publication: 2018 Mar 01 (Print Publication: 2018).
DOI: 10.1186/s13068-018-1052-9
Abstrakt: Background: The global demand for affordable carbon has never been stronger, and there is an imperative in many industrial processes to use waste streams to make products. Gas-fermenting acetogens offer a potential solution and several commercial gas fermentation plants are currently under construction. As energy limits acetogen metabolism, supply of H 2 should diminish substrate loss to CO 2 and facilitate production of reduced and energy-intensive products. However, the effects of H 2 supply on CO-grown acetogens have yet to be experimentally quantified under controlled growth conditions.
Results: Here, we quantify the effects of H 2 supplementation by comparing growth on CO, syngas, and a high-H 2 CO gas mix using chemostat cultures of Clostridium autoethanogenum . Cultures were characterised at the molecular level using metabolomics, proteomics, gas analysis, and a genome-scale metabolic model. CO-limited chemostats operated at two steady-state biomass concentrations facilitated co-utilisation of CO and H 2 . We show that H 2 supply strongly impacts carbon distribution with a fourfold reduction in substrate loss as CO 2 (61% vs. 17%) and a proportional increase of flux to ethanol (15% vs. 61%). Notably, H 2 supplementation lowers the molar acetate/ethanol ratio by fivefold. At the molecular level, quantitative proteome analysis showed no obvious changes leading to these metabolic rearrangements suggesting the involvement of post-translational regulation. Metabolic modelling showed that H 2 availability provided reducing power via H 2 oxidation and saved redox as cells reduced all the CO 2 to formate directly using H 2 in the Wood-Ljungdahl pathway. Modelling further indicated that the methylene-THF reductase reaction was ferredoxin reducing under all conditions. In combination with proteomics, modelling also showed that ethanol was synthesised through the acetaldehyde:ferredoxin oxidoreductase (AOR) activity.
Conclusions: Our quantitative molecular analysis revealed that H 2 drives rearrangements at several layers of metabolism and provides novel links between carbon, energy, and redox metabolism advancing our understanding of energy conservation in acetogens. We conclude that H 2 supply can substantially increase the efficiency of gas fermentation and thus the feed gas composition can be considered an important factor in developing gas fermentation-based bioprocesses.
Databáze: MEDLINE
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