skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Influence of Energy and Electron Availability on In Vivo Methane and Hydrogen Production by a Variant Molybdenum Nitrogenase

Abstract

ABSTRACT The anoxygenic phototrophic bacteriumRhodopseudomonas palustrisproduces methane (CH 4) from carbon dioxide (CO 2) and hydrogen (H 2) from protons (H +) when it expresses a variant form of molybdenum (Mo) nitrogenase that has two amino acid substitutions near its active site. We examined the influence of light energy and electron availability onin vivoproduction of these biofuels. Nitrogenase activity requires large amounts of ATP, and cells exposed to increasing light intensities produced increasing amounts of CH 4and H 2. As expected for a phototroph, intracellular ATP increased with increasing light intensity, but there was only a loose correlation between ATP content and CH 4and H 2production. There was a much stronger correlation between decreased intracellular ADP and increased gas production with increased light intensity, suggesting that the rate-limiting step for CH 4and H 2production byR. palustrisis inhibition of nitrogenase by ADP. Increasing the amounts of electrons available to nitrogenase by providing cells with organic alcohols, using nongrowing cells, blocking electrons from entering the Calvin cycle, or blocking H 2uptake resulted in higher yields of H 2and, in some cases, CH 4. Our results provide a more complete understanding of the constraints on nitrogenase-based production of biofuels. IMPORTANCEA variant form ofmore » Mo nitrogenase catalyzes the conversion of CO 2and protons to the biofuels CH 4and H 2. A constant supply of electrons and ATP is needed to drive these reduction reactions. The bacteriumR. palustrisgenerates ATP from light and has a versatile metabolism that makes it ideal for manipulating electron availability intracellularly. We therefore explored its potential as a biocatalyst for CH 4and H 2production. We found that intracellular ADP had a major effect on biofuel production, more pronounced than the effect caused by ATP. This is probably due to inhibition of nitrogenase activity by ADP. In general, the amount of CH 4produced by the variant nitrogenasein vivowas affected by electron availability much less than was the amount of H 2produced. This study shows the nature of constraints onin vivobiofuel production by variant Mo nitrogenase.« less

Authors:
; ORCiD logo;
Publication Date:
Research Org.:
Energy Frontier Research Centers (EFRC) (United States). Center for Biological Electron Transfer and Catalysis (BETCy); Montana State Univ., Bozeman, MT (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1566725
DOE Contract Number:  
SC0012518
Resource Type:
Journal Article
Journal Name:
Applied and Environmental Microbiology
Additional Journal Information:
Journal Volume: 85; Journal Issue: 9; Journal ID: ISSN 0099-2240
Publisher:
American Society for Microbiology
Country of Publication:
United States
Language:
English
Subject:
solar (fuels), biofuels (including algae and biomass), bio-inspired, hydrogen and fuel cells

Citation Formats

Zheng, Yanning, Harwood, Caroline S., and Müller, Volker. Influence of Energy and Electron Availability on In Vivo Methane and Hydrogen Production by a Variant Molybdenum Nitrogenase. United States: N. p., 2019. Web. doi:10.1128/aem.02671-18.
Zheng, Yanning, Harwood, Caroline S., & Müller, Volker. Influence of Energy and Electron Availability on In Vivo Methane and Hydrogen Production by a Variant Molybdenum Nitrogenase. United States. doi:10.1128/aem.02671-18.
Zheng, Yanning, Harwood, Caroline S., and Müller, Volker. Fri . "Influence of Energy and Electron Availability on In Vivo Methane and Hydrogen Production by a Variant Molybdenum Nitrogenase". United States. doi:10.1128/aem.02671-18.
@article{osti_1566725,
title = {Influence of Energy and Electron Availability on In Vivo Methane and Hydrogen Production by a Variant Molybdenum Nitrogenase},
author = {Zheng, Yanning and Harwood, Caroline S. and Müller, Volker},
abstractNote = {ABSTRACT The anoxygenic phototrophic bacteriumRhodopseudomonas palustrisproduces methane (CH4) from carbon dioxide (CO2) and hydrogen (H2) from protons (H+) when it expresses a variant form of molybdenum (Mo) nitrogenase that has two amino acid substitutions near its active site. We examined the influence of light energy and electron availability onin vivoproduction of these biofuels. Nitrogenase activity requires large amounts of ATP, and cells exposed to increasing light intensities produced increasing amounts of CH4and H2. As expected for a phototroph, intracellular ATP increased with increasing light intensity, but there was only a loose correlation between ATP content and CH4and H2production. There was a much stronger correlation between decreased intracellular ADP and increased gas production with increased light intensity, suggesting that the rate-limiting step for CH4and H2production byR. palustrisis inhibition of nitrogenase by ADP. Increasing the amounts of electrons available to nitrogenase by providing cells with organic alcohols, using nongrowing cells, blocking electrons from entering the Calvin cycle, or blocking H2uptake resulted in higher yields of H2and, in some cases, CH4. Our results provide a more complete understanding of the constraints on nitrogenase-based production of biofuels. IMPORTANCEA variant form of Mo nitrogenase catalyzes the conversion of CO2and protons to the biofuels CH4and H2. A constant supply of electrons and ATP is needed to drive these reduction reactions. The bacteriumR. palustrisgenerates ATP from light and has a versatile metabolism that makes it ideal for manipulating electron availability intracellularly. We therefore explored its potential as a biocatalyst for CH4and H2production. We found that intracellular ADP had a major effect on biofuel production, more pronounced than the effect caused by ATP. This is probably due to inhibition of nitrogenase activity by ADP. In general, the amount of CH4produced by the variant nitrogenasein vivowas affected by electron availability much less than was the amount of H2produced. This study shows the nature of constraints onin vivobiofuel production by variant Mo nitrogenase.},
doi = {10.1128/aem.02671-18},
journal = {Applied and Environmental Microbiology},
issn = {0099-2240},
number = 9,
volume = 85,
place = {United States},
year = {2019},
month = {3}
}

Works referenced in this record:

Complete genome sequence of the metabolically versatile photosynthetic bacterium Rhodopseudomonas palustris
journal, December 2003

  • Larimer, Frank W; Chain, Patrick; Hauser, Loren
  • Nature Biotechnology, Vol. 22, Issue 1, p. 55-61
  • DOI: 10.1038/nbt923