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Hydrogen as a Co-electron Donor for Chain Elongation With Complex Communities

Electron donor scarcity is seen as one of the major issues limiting economic production of medium-chain carboxylates from waste streams. Previous studies suggest that co-fermentation of hydrogen in microbial communities that realize chain elongation relieves this limitation. To better understand how...

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Autores principales: Baleeiro, Flávio C. F., Kleinsteuber, Sabine, Sträuber, Heike
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Frontiers Media S.A. 2021
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8059637/
https://www.ncbi.nlm.nih.gov/pubmed/33898406
http://dx.doi.org/10.3389/fbioe.2021.650631
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author Baleeiro, Flávio C. F.
Kleinsteuber, Sabine
Sträuber, Heike
author_facet Baleeiro, Flávio C. F.
Kleinsteuber, Sabine
Sträuber, Heike
author_sort Baleeiro, Flávio C. F.
collection PubMed
description Electron donor scarcity is seen as one of the major issues limiting economic production of medium-chain carboxylates from waste streams. Previous studies suggest that co-fermentation of hydrogen in microbial communities that realize chain elongation relieves this limitation. To better understand how hydrogen co-feeding can support chain elongation, we enriched three different microbial communities from anaerobic reactors (A, B, and C with ascending levels of diversity) for their ability to produce medium-chain carboxylates from conventional electron donors (lactate or ethanol) or from hydrogen. In the presence of abundant acetate and CO(2), the effects of different abiotic parameters (pH values in acidic to neutral range, initial acetate concentration, and presence of chemical methanogenesis inhibitors) were tested along with the enrichment. The presence of hydrogen facilitated production of butyrate by all communities and improved production of i-butyrate and caproate by the two most diverse communities (B and C), accompanied by consumption of acetate, hydrogen, and lactate/ethanol (when available). Under optimal conditions, hydrogen increased the selectivity of conventional electron donors to caproate from 0.23 ± 0.01 mol e(–)/mol e(–) to 0.67 ± 0.15 mol e(–)/mol e(–) with a peak caproate concentration of 4.0 g L(–1). As a trade-off, the best-performing communities also showed hydrogenotrophic methanogenesis activity by Methanobacterium even at high concentrations of undissociated acetic acid of 2.9 g L(–1) and at low pH of 4.8. According to 16S rRNA amplicon sequencing, the suspected caproate producers were assigned to the family Anaerovoracaceae (Peptostreptococcales) and the genera Megasphaera (99.8% similarity to M. elsdenii), Caproiciproducens, and Clostridium sensu stricto 12 (97–100% similarity to C. luticellarii). Non-methanogenic hydrogen consumption correlated to the abundance of Clostridium sensu stricto 12 taxa (p < 0.01). If a robust methanogenesis inhibition strategy can be found, hydrogen co-feeding along with conventional electron donors can greatly improve selectivity to caproate in complex communities. The lessons learned can help design continuous hydrogen-aided chain elongation bioprocesses.
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spelling pubmed-80596372021-04-22 Hydrogen as a Co-electron Donor for Chain Elongation With Complex Communities Baleeiro, Flávio C. F. Kleinsteuber, Sabine Sträuber, Heike Front Bioeng Biotechnol Bioengineering and Biotechnology Electron donor scarcity is seen as one of the major issues limiting economic production of medium-chain carboxylates from waste streams. Previous studies suggest that co-fermentation of hydrogen in microbial communities that realize chain elongation relieves this limitation. To better understand how hydrogen co-feeding can support chain elongation, we enriched three different microbial communities from anaerobic reactors (A, B, and C with ascending levels of diversity) for their ability to produce medium-chain carboxylates from conventional electron donors (lactate or ethanol) or from hydrogen. In the presence of abundant acetate and CO(2), the effects of different abiotic parameters (pH values in acidic to neutral range, initial acetate concentration, and presence of chemical methanogenesis inhibitors) were tested along with the enrichment. The presence of hydrogen facilitated production of butyrate by all communities and improved production of i-butyrate and caproate by the two most diverse communities (B and C), accompanied by consumption of acetate, hydrogen, and lactate/ethanol (when available). Under optimal conditions, hydrogen increased the selectivity of conventional electron donors to caproate from 0.23 ± 0.01 mol e(–)/mol e(–) to 0.67 ± 0.15 mol e(–)/mol e(–) with a peak caproate concentration of 4.0 g L(–1). As a trade-off, the best-performing communities also showed hydrogenotrophic methanogenesis activity by Methanobacterium even at high concentrations of undissociated acetic acid of 2.9 g L(–1) and at low pH of 4.8. According to 16S rRNA amplicon sequencing, the suspected caproate producers were assigned to the family Anaerovoracaceae (Peptostreptococcales) and the genera Megasphaera (99.8% similarity to M. elsdenii), Caproiciproducens, and Clostridium sensu stricto 12 (97–100% similarity to C. luticellarii). Non-methanogenic hydrogen consumption correlated to the abundance of Clostridium sensu stricto 12 taxa (p < 0.01). If a robust methanogenesis inhibition strategy can be found, hydrogen co-feeding along with conventional electron donors can greatly improve selectivity to caproate in complex communities. The lessons learned can help design continuous hydrogen-aided chain elongation bioprocesses. Frontiers Media S.A. 2021-03-31 /pmc/articles/PMC8059637/ /pubmed/33898406 http://dx.doi.org/10.3389/fbioe.2021.650631 Text en Copyright © 2021 Baleeiro, Kleinsteuber and Sträuber. https://creativecommons.org/licenses/by/4.0/This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
spellingShingle Bioengineering and Biotechnology
Baleeiro, Flávio C. F.
Kleinsteuber, Sabine
Sträuber, Heike
Hydrogen as a Co-electron Donor for Chain Elongation With Complex Communities
title Hydrogen as a Co-electron Donor for Chain Elongation With Complex Communities
title_full Hydrogen as a Co-electron Donor for Chain Elongation With Complex Communities
title_fullStr Hydrogen as a Co-electron Donor for Chain Elongation With Complex Communities
title_full_unstemmed Hydrogen as a Co-electron Donor for Chain Elongation With Complex Communities
title_short Hydrogen as a Co-electron Donor for Chain Elongation With Complex Communities
title_sort hydrogen as a co-electron donor for chain elongation with complex communities
topic Bioengineering and Biotechnology
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8059637/
https://www.ncbi.nlm.nih.gov/pubmed/33898406
http://dx.doi.org/10.3389/fbioe.2021.650631
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