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Spotlight on the Energy Harvest of Electroactive Microorganisms: The Impact of the Applied Anode Potential

Electroactive microorganisms (EAM) harvest energy by reducing insoluble terminal electron acceptors (TEA) including electrodes via extracellular electron transfer (EET). Therefore, compared to microorganisms respiring soluble TEA, an adapted approach is required for thermodynamic analyses. In EAM, t...

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Autores principales: Korth, Benjamin, Harnisch, Falk
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Frontiers Media S.A. 2019
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6606774/
https://www.ncbi.nlm.nih.gov/pubmed/31293531
http://dx.doi.org/10.3389/fmicb.2019.01352
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author Korth, Benjamin
Harnisch, Falk
author_facet Korth, Benjamin
Harnisch, Falk
author_sort Korth, Benjamin
collection PubMed
description Electroactive microorganisms (EAM) harvest energy by reducing insoluble terminal electron acceptors (TEA) including electrodes via extracellular electron transfer (EET). Therefore, compared to microorganisms respiring soluble TEA, an adapted approach is required for thermodynamic analyses. In EAM, the thermodynamic frame (i.e., maximum available energy) is restricted as only a share of the energy difference between electron donor and TEA is exploited via the electron-transport chain to generate proton-motive force being subsequently utilized for ATP synthesis. However, according to a common misconception, the anode potential is suggested to co-determine the thermodynamic frame of EAM. By comparing the model organism Geobacter spp. and microorganisms respiring soluble TEA, we reason that a considerable part of the electron-transport chain of EAM performing direct EET does not contribute to the build-up of proton-motive force and thus, the anode potential does not co-determine the thermodynamic frame. Furthermore, using a modeling platform demonstrates that the influence of anode potential on energy harvest is solely a kinetic effect. When facing low anode potentials, NADH is accumulating due to a slow direct EET rate leading to a restricted exploitation of the thermodynamic frame. For anode potentials ≥ 0.2 V (vs. SHE), EET kinetics, NAD(+)/NADH ratio as well as exploitation of the thermodynamic frame are maximized, and a further potential increase does not result in higher energy harvest. Considering the limited influence of the anode potential on energy harvest of EAM is a prerequisite to improve thermodynamic analyses, microbial resource mining, and to transfer microbial electrochemical technologies (MET) into practice.
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spelling pubmed-66067742019-07-10 Spotlight on the Energy Harvest of Electroactive Microorganisms: The Impact of the Applied Anode Potential Korth, Benjamin Harnisch, Falk Front Microbiol Microbiology Electroactive microorganisms (EAM) harvest energy by reducing insoluble terminal electron acceptors (TEA) including electrodes via extracellular electron transfer (EET). Therefore, compared to microorganisms respiring soluble TEA, an adapted approach is required for thermodynamic analyses. In EAM, the thermodynamic frame (i.e., maximum available energy) is restricted as only a share of the energy difference between electron donor and TEA is exploited via the electron-transport chain to generate proton-motive force being subsequently utilized for ATP synthesis. However, according to a common misconception, the anode potential is suggested to co-determine the thermodynamic frame of EAM. By comparing the model organism Geobacter spp. and microorganisms respiring soluble TEA, we reason that a considerable part of the electron-transport chain of EAM performing direct EET does not contribute to the build-up of proton-motive force and thus, the anode potential does not co-determine the thermodynamic frame. Furthermore, using a modeling platform demonstrates that the influence of anode potential on energy harvest is solely a kinetic effect. When facing low anode potentials, NADH is accumulating due to a slow direct EET rate leading to a restricted exploitation of the thermodynamic frame. For anode potentials ≥ 0.2 V (vs. SHE), EET kinetics, NAD(+)/NADH ratio as well as exploitation of the thermodynamic frame are maximized, and a further potential increase does not result in higher energy harvest. Considering the limited influence of the anode potential on energy harvest of EAM is a prerequisite to improve thermodynamic analyses, microbial resource mining, and to transfer microbial electrochemical technologies (MET) into practice. Frontiers Media S.A. 2019-06-26 /pmc/articles/PMC6606774/ /pubmed/31293531 http://dx.doi.org/10.3389/fmicb.2019.01352 Text en Copyright © 2019 Korth and Harnisch. http://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 Microbiology
Korth, Benjamin
Harnisch, Falk
Spotlight on the Energy Harvest of Electroactive Microorganisms: The Impact of the Applied Anode Potential
title Spotlight on the Energy Harvest of Electroactive Microorganisms: The Impact of the Applied Anode Potential
title_full Spotlight on the Energy Harvest of Electroactive Microorganisms: The Impact of the Applied Anode Potential
title_fullStr Spotlight on the Energy Harvest of Electroactive Microorganisms: The Impact of the Applied Anode Potential
title_full_unstemmed Spotlight on the Energy Harvest of Electroactive Microorganisms: The Impact of the Applied Anode Potential
title_short Spotlight on the Energy Harvest of Electroactive Microorganisms: The Impact of the Applied Anode Potential
title_sort spotlight on the energy harvest of electroactive microorganisms: the impact of the applied anode potential
topic Microbiology
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6606774/
https://www.ncbi.nlm.nih.gov/pubmed/31293531
http://dx.doi.org/10.3389/fmicb.2019.01352
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