The thermodynamic landscape of methanogenic PAH degradation.
Bottom Line: Depending on the in situ conditions the energetically most favourable pathway for the PAH-degrading organisms is oxidation to H(2)/CO(2) or conversion into acetate.These are not necessarily the pathways that prevail in the environment.This may be because the kinetic theory of optimal length of metabolic pathways suggests that PAH degraders may have evolved towards incomplete oxidation to acetate plus H(2) as the optimal pathway.
Affiliation: School of Civil Engineering and Geosciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK. Jan.Dolfing@ncl.ac.ukShow MeSH
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Mentions: Thermodynamic calculations for the methanogenic degradation of five different PAHs (naphthalene, phenanthrene, anthracene, pyrene and chrysene) yielded ΔGo values in the range of −208.8 to −331.4 kJ mol−1 (Table 1). Calculated on a per mole CH4 produced basis this range collapsed to −27.1 to −34.8 kJ mol−1. The change in Gibbs free energy values per mole of CH4 produced increased with increasing C/H ratios: the less hydrogen substituents present on the aromatic ring, the more energy available from the methanogenic degradation of these compounds (Fig. 1).
Affiliation: School of Civil Engineering and Geosciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK. Jan.Dolfing@ncl.ac.uk