Archives of Microbiology

, Volume 155, Issue 1, pp 82–88 | Cite as

Energetics of syntrophic ethanol oxidation in defined chemostat cocultures

1. Energy requirement for H2 production and H2 oxidation
  • H. -J. Seitz
  • B. Schink
  • N. Pfennig
  • R. Conrad
Original Papers


The ethanol-oxidizing, proton-reducing Pelobacter acetylenicus was grown in chemostat cocultures with either Acetobacterium woodii, Methanobacterium bryantii, or Desulfovibrio desulfuricans. Stable steady state conditions with tightly coupled growth were reached at various dilution rates between 0.02 and 0.14 h-1. Both ethanol and H2 steady state concentrations increased with growth rate and were lower in cocultures with the sulfate reducer < methanogen < homoacetogen. Due to the higher affinity for H2, D. desulfuricans outcompeted M. bryantii, and this one A. woodii when inoculated in cocultures with P. acetylenicus. Cocultures with A. woodii had lower H2 steady state concentrations when bicarbonate reduction was replaced by the energetically more favourable caffeate reduction. Similarly, cocultures with D. desulfuricans had lower H2 concentrations with nitrate than with sulfate as electron acceptor. The Gibbs free energy (ΔG) available to the H2-producing P. acetylenicus was independent of growth rate and the H2-utilizing partner, whereas the ΔG available to the latter increased with growth rate and the energy yielding potential of the H2 oxidation reaction. The “critical” Gibbs free energy (ΔGc), i.e. the minimum energy required for H2 production and H2 oxidation, was-5.5 to-8.0 kJ mol-1 H2 for P. acetylenicus,-5.1 to-6.3 kJ mol-1 H2 for A. woodii,-7.5 to-9.1 kJ mol-1 H2 for M. bryantii, and-10.3 to-12.3 kJ mol-1 H2 for D. desulfuricans. Obviously, the potentially available energy was used more efficiently by homoacetogens > methanogens > sulfate reducers.

Key words

Homoacetogenesis Methanogenesis Sulfate reduction Caffeate reduction Nitrate reduction Interspecies H2 transfer Affinity H2 threshold “Critical” Gibbs free energy 


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Copyright information

© Springer-Verlag 1990

Authors and Affiliations

  • H. -J. Seitz
    • 1
  • B. Schink
    • 2
  • N. Pfennig
    • 1
  • R. Conrad
    • 1
  1. 1.Fakultät für BiologieUniversität KonstanzKonstanzFederal Republic of Germany
  2. 2.Lehrstuhl Mikrobiologie IUniversität TübingenTübingenFederal Republic of Germany

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