TABLE 12.

Catabolic stoichiometry of ethanol, acetic acid, and lactic acid formation in cellulolytic anaerobes

Step or enzymeReactiona
GlycolysisGlucose + 2ADP + 2Pi + 2NAD+ → 2 Pyruvate + 2 ATP + 2 NADH + 4H+
Pyruvate:ferredoxin oxidoreductase{MYE/G + MYA/G} {Pyruvate + CoASH + Fd(ox) → Acetyl-CoA + Fd(red) + CO2 + H+}
NADH:ferredoxin oxidoreductase{MYE/GMYA/G} {Fd(red) + NAD+ + 2H+ → Fd(ox) + NADH + H+}
Acetaldehyde dehydrogenaseMYE/G {Acetyl-CoA + NADH + H+ → Acetaldehyde + CoASH + NAD+}
Ethanol dehydrogenaseMYE/G {Acetaldehyde + NADH + H+ → Ethanol + NAD+}
PhosphotransacetylaseMYA/G {Acetyl-CoA + Pi → Acetyl phosphate + CoASH}
Acetate kinaseMYA/G {Acetyl phosphate + ADP → Acetate + ATP + H+}
Hydrogenase2 MYA/G {Fd(red) + 2H+ → H2 + Fd(ox)}
Lactate dehydrogenaseMYL/G {Pyruvate + NADH + H+ → Lactate + NAD+}
OverallGlucose + {2 + MYA/G} ADP + {2 + MYA/G}PiMYE/GEthanol + MYE/GEthanol + MYA/GAcetate + MYL/GLactate + {MYEt/Glu + MYA/G}CO2 + {MYL/G + MYA/G}H+ + 2MYA/GH2 + {2 + MYA/G}ATP
  • a MYE/G is the molar ethanol yield (moles of ethanol per mole of hexose);MYA/G is the molar acetic acid yield (moles of acetic acid per mole of hexose); MYL/G is the molar lactic acid yield (moles of lactic acid/mole of hexose). Note: MYE/G + MYA/G + MYL/G = 2.