(194w) Metabolic Engineering of Clostridium Aceticum for Acetone, Butanol and Ethanol Fermentation

Clostridium aceticum is a homoacetogenic bacteria which converts CO2 and H2 to acetate without losing any carbon, thus resulting in a higher potential yield than fermentation from heteroacetogenic bacteria such as Clostridium acetobutylicum for ABE (acetone-butanol-ethanol) fermentation. However, wild-type C. aceticum only produces acetate, and no paper has been published on the metabolic engineering of C. aceticum. 

In this study, we established methods for metabolic engineering of Clostridium aceticum DSM 1496 (ATCC 35044). Acetone and solvent production by C. aceticum will be studied individually and together. For acetone production, butyrate-acetoacetate CoA-transferase gene (ctfA/B) and acetoacetate decarboxylase (adc) gene from Clostridium acetobutylicum ATCC 824 will be introduced into C. aceticum. Also, ethanol and butanol production pathway was introduced by overexpressing aldehyde/alcohol dehydrogenase 2 (adhE2), thiolase (thl), butanol dehydrogenase (bdh) and BCS cluster (including crotonase (crt), putative butyryl-CoA dehydrogenase (BCD), electron-transfer flavoprotein (etf), and 3-hydroxybutyryl-CoA dehydrogenase (hbd) genes) from Clostridium acetobutylicum ATCC 824. Fermentation kinetics will be studied from sugar and CO2, as well as from CO2 and H2. This study aims at producing chemicals from CO2, H2 and sugar, which could help alleviate CO2 emission problem as well as increase fermentation yield.