Impact of exogenous acetate on ethanol formation and gene transcription for key enzymes in Clostridium autoethanogenum grown on CO

•Ethanol production in C. autoethanogenum was improved in the presence of exogenous acetate.•13C abundance in ethanol increased with the amount of 13C-labeled acetate supplemented.•Transcriptional level of pta gene was down-regulated in the presence of exogenous acetate.•Genes CAETHG_0102, CAETHG_3005, CAETHG_1841 and CAETHG_1813 were highly up-regulated at higher levels of exogenous acetate.