Figure 1.

Schematic representation of reverse beta-oxidation cycle, adapted from Angenent et al.¹. Briefly, the metabolism first converts EtOH to acetyl-CoA, part of which (one molecule in six) is oxidised to acetate for ATP-generation. The remaining acetyl-CoA is combined with acetyl-CoA cycled in the reverse β-oxidation cycle, producing butyryl-CoA. This butyryl-CoA can either be converted to butyrate, or immediately be cycled again (dashed arrow), yielding hexanoyl-CoA, which in turn can be converted to hexanoate. Simultaneously 6 protons are pumped across the cell membrane per cycle, required to balance the NADH/NAD⁺-pool over the entire metabolism. This process generates a proton motive force, which allows to recover more of the energy generated in the cycle (in total 2.5 ATP per cycle).