Effect of dilution on methanogenesis, hydrogen turnover and interspecies hydrogen transfer in anoxic paddy soil |
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Authors: | Ralf Conrad Monika Babbel |
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Affiliation: | Universität Konstanz, Fakultät für Biologie, Konstanz, F.R.G. |
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Abstract: | Abstract Dilution of anoxic slurries of paddy soil resulted in a proportional decrease of the rates of total methanogenesis and the rate constants of H2 turnover per gram soil. Dilution did not affect the fraction of H2/CO2-dependent methanogenesis which made up 22% of total CH4 production. However, dilution resulted in a ten fold decrease of the H2 steady state partial pressure from approximately 4 to 0.4 Pa indicating that H2/CO2-dependent methanogenesis was more or less independent of the H2 pool. The rates of H2 production calculated from the H2 turnover rate constants and the H2 steady state partial pressures accounted for only < 5% of H2/CO2-dependent methanogenesis in undiluted soil slurries and for even less after dilution. Upon dilution, the Gibbs free energy available for H2/CO2-dependent methanogenesis decreased from −28.4 to only −5.6 kJ per mol. The results indicate that methane was mainly produced from interspecies H2 transfer within syntrophic bacterial associations and was not significantly affected by the outside H2 pool. |
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Keywords: | H2 partial pressure Gibbs free energy Syntrophic associations Interspecies formate transfer |
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