(228bj) Production of Ethanol and Butanol from CO2 and H2 By Clostridium Aceticum

Clostridium aceticum is a homoacetogenic bacteria which converts CO₂ and H₂ to acetate without losing any carbon, thus resulting in a higher yield and titer than fermentation from heteroacetogenic bacteria such as Clostridium ljungdahlii and Clostridium carboxidivorans.

In this study, Clostridium aceticum DSM 1496 (ATCC 35044) was used as a host to produce ethanol and butanol by overexpressing aldehyde ferredoxin oxidoreductase (AOR) from Clostridium carboxidivorans, and aldehyde/alcohol dehydrogenase 2 (adhE2), thiolase (thl), butanol dehydrogenase (bdh) and BCS cluster (includingcrotonase (crt), putative butyryl-CoA dehydrogenase (BCD), electron-transfer flavoprotein (etf), and 3-hydroxybutyryl-CoA dehydrogenase (hbd) genes) fromClostridium acetobutylicum ATCC 824. Ethanol titer of 8.13 g/L was obtained in C. aceticum overexpressing adhE2, and 4.86 g/L in C. aceticum overexpressing AOR. Butanol production was low in C. aceticum overexpressing adhE2, thl and BCS, but increased significantly in C. aceticum overexpressing bdh, thl and BCS. These results suggest that C. aceticum is a promising heterologous host for ethanol and butanol production from CO₂.