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

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