Butanol Production Improvement By Metabolically Engineered Clostridium Tyrobutyricum with Proteomics Analysis

Some metabolically engineered clostridia have the potential to economically produce biobutanol, a sustainable and environmentally friendly fuel with similar energy intensity to petroleum gas. The goals of this study were to develop a fundamental understanding of carbon redistribution to butanol and achieve higher butanol production using engineered C. tyrobutyricum ATCC 25755. The 2-L free-cell fermentations were performed in stirred tank bioreactors at pH 6.0 and 37^oC using butyrate producing strains (control) and a high butanol producing ACKKO-adhE2 mutant (butanol titer of 14-16 g/L). The global proteomics profiling of these strains were investigated and compared. It is found that, as compared to wild type, the ACKKO-adhE2 had decreased expression of thiolase (thl), 3-hydroxybutyryl-CoA dehydrogenase (hbd) and crotonase (crt) and high expression of heterologous bifunctional acetaldehyde/alcohol dehydrogenase (adhE2). These findings indicated that we could further improve butanol production by refluxing carbon to butyryl-CoA.