TABLE 1

Possible reactions occurring during oleate conversion in the presence and absence of methanogenesis and during utilization of isethionate by Desulfovibrio sp.

Reaction no.Equation and reactionΔG0′ (kJ/reaction)a
1 β-Oxidation of oleate
C18H33O2 + 16H2O → 9C2H3O2 + 15H2 + 8H+325.86
2 Methanogenesis from hydrogen
4H2 + HCO3 + H+ → CH4 + 3H2O−135.58
3 Desulfonation of isethionate
C2H5O4S + H2O → C2H3O2 + SO32− + 2H+ + H2−48.70
4 Disproportionation of sulfite
4SO32− + H+ → 3SO42− + HS−235.52
4.1 Sulfite oxidation
SO32− + H2O → SO42− + H2−20.83
4.2 Sulfite reduction
SO32− + 3H2 + H+ → HS + 3H2O−173.03
5 Sulfate reduction
SO42− + 4H2 +H+ → HS + 4H2O−152.20
6 Overall reaction for isethionate conversion without hydrogen
2C2H5O4S → 2C2H3O2 + SO42− + HS + 3H+−291.26
7 Overall reaction for isethionate conversion with hydrogen
C2H5O4S + 2H2 → C2H3O2 + HS + H+ + 2H2O−221.73
8 Overall reaction for oleate and isethionate conversion
C18H33O2 + 7.5C2H5O4S + H2O → 16.5C2H3O2 + 7.5HS + 15.5H+−1,337.12
9 Overall reaction for methanogenic oleate conversion
C18H33O2 + 4.75H2O + 3.75HCO3 → 9C2H3O2 + 3.75CH4 + 4.25H+−182.57
  • a ΔG0' was calculated under standard conditions (solute concentrations of 1 mol/liter, gas partial pressure of 1 × 105 Pa, T = 25°C) at pH 7. Free energies of formation for isethionate and oleate were estimated according to reference 51; for the other compounds involved in the reactions, the values were obtained from reference 52.