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Table 1 Overview of main catabolic conversions shown occurring during continuous methanol-based propionate and acetate elongation under anaerobic conditions at 308 K and pH 5.8 with the Gibbs free energy of the reactions

From: Continuous n-valerate formation from propionate and methanol in an anaerobic chain elongation open-culture bioreactor

Nr Description Catabolic reaction ΔG 1r (kJ/reaction)
1 Methylotrophic methanogenesis [32] \(4{\text{CH}}_{3} {\text{OH}} \to 3{\text{CH}}_{4} + {\text{HCO}}_{3}^{ - } + {\text{H}}_{2} {\text{O}} + {\text{H}}^{ + }\) − 310.8
2 Methylotrophic acetogenesis [33] \(4 {\text{CH}}_{3} {\text{OH}} + 2{\text{HCO}}_{3}^{ - } \to 3{\text{CH}}_{3} {\text{COO}}^{ - } + {\text{H}}^{ + } + 4{\text{H}}_{2} {\text{O}}\) − 178.7
3 n-Valerate formation from methanol and propionate \(2{\text{CH}}_{3} {\text{OH}} + {\text{C}}_{3} {\text{H}}_{5} {\text{O}}_{2}^{ - } \to {\text{C}}_{5} {\text{H}}_{9} {\text{O}}_{2}^{ - } + 2{\text{H}}_{2} {\text{O}}\) − 106.1
4 n-Butyrate formation from methanol and acetate [24] \(2{\text{CH}}_{3} {\text{OH}} + {\text{CH}}_{3} {\text{COO}}^{ - } \to {\text{CH}}_{3} \left( {{\text{CH}}_{2} } \right)_{2} {\text{COO}}^{ - } + 2{\text{H}}_{2} {\text{O}}\) − 106.1
5 Iso-butyrate formation from methanol and acetate \(2{\text{CH}}_{3} {\text{OH}} + {\text{CH}}_{3} {\text{COO}}^{ - } \to \left( {{\text{CH}}_{3} } \right)_{2} {\text{CHCOO}}^{ - } + 2{\text{H}}_{2} {\text{O}}\) − 106.1
6 Acetotrophic methanogenesis [34] \({\text{CH}}_{3} {\text{COO}}^{ - } + {\text{H}}_{2} {\text{O}} \to {\text{CH}}_{4} + {\text{HCO}}_{3}^{ - }\) − 49.9
7 Hydrogenogenic propionate degradation [35, 36] \({\text{CH}}_{3} {\text{CH}}_{2} {\text{COO}}^{ - } + 3{\text{H}}_{2} {\text{O}} \to {\text{CH}}_{3} {\text{COO}}^{ - } + {\text{HCO}}_{3}^{ - } + {\text{H}}^{ + } + 3{\text{H}}_{2}\) 26.7 with pH2 100 Pa
8 Hydrogenotrophic methanogenesis [37] \(4{\text{H}}_{2} + {\text{HCO}}_{3}^{ - } + {\text{H}}^{ + } \to {\text{CH}}_{4} + 3{\text{H}}_{2} {\text{O}}\) − 68.4 with pH2 100 Pa
9 Hydrogenotrophic acetogenesis [38] \(4{\text{H}}_{2} + 2{\text{HCO}}_{3}^{ - } + {\text{H}}^{ + } \to {\text{CH}}_{3} {\text{COO}}^{ - } + 4{\text{H}}_{2} {\text{O}}\) − 36.1 with pH2 100 Pa
  1. The calculation of the Gibbs free energy is shown in Additional file 1 [67, 68]