INFLUENCE OF TEMPERATURE ON ENERGETICS OF HYDROGEN METABOLISM IN HOMOACETOGENIC, METHANOGENIC, AND OTHER ANAEROBIC-BACTERIA

Hydrogen consumption by various thermophilic, mesophilic and/or psychrotrophic homoacetogens and methanogens was measured at temperatures between 4 and 80°C. Within the tolerated temperature range H2 was consumed until a final H2 threshold partial pressure was reached. H2 thresholds generally decreased with temperature, parallel to the values calculated from the thermodynamics prevailing under culture conditions, i.e. the Gibbs free energy (ΔG) of H2 oxidation corrected for temperature by both the free-energy form of the Nernst equation and the Van't Hoff equation. The difference between the observed and the calculated H2 partial pressures gives the minimum energy required for H2 utilization being about-5 to-6 kJ/mol H2 for the homoacetogenes and-9 to-12 kJ/mol H2 for methanogens. The temperature dependence of the standard Gibbs free energy (ΔG0) as described by the Van't Hoff equation apparently became the more important for thermodynamics as well as H2 thresholds the more the temperature deviated from standard conditions (i.e. 25°C). Correction factors for calculation of temperature-corrected ΔGinfTsup0are presented for various H2-producing and H2-consuming reactions. © 1990 Springer-Verlag.