The original version of this Article contained errors in the Discussion section, where reference 34 was incorrectly cited as reference 25. Consequently, “Spirito et al.25 also observed a decreased conversion rate when feeding a chain-elongating reactor microbiome with mainly ethanol. This could explain why previous studies with shorter incubation times reported no metabolic activity in the absence of acetate25,35. The mechanism that underlies this change in rate remains elusive. Spirito et al.25 proposed a thermodynamic constraint on the rate due to increased hydrogen partial pressures, but in our experiments pH2 was low due to continuous sparging and we still observed low rates.” now reads: “Spirito et al.34 also observed a decreased conversion rate when feeding a chain-elongating reactor microbiome with mainly ethanol. This could explain why previous studies with shorter incubation times reported no metabolic activity in the absence of acetate34,35. The mechanism that underlies this change in rate remains elusive. Spirito et al.34 proposed a thermodynamic constraint on the rate due to increased hydrogen partial pressures, but in our experiments pH2 was low due to continuous sparging and we still observed low rates.” The original Article has been corrected.