Engineering Escherichia coli for High Selective Production of Butyric Acid

Chiang, C. J., China Medical University
Chao, Y. P., Feng Chia University

Butyric acid has many important applications in industry and is mainly produced by the petroleum-based process. The bio-based production method for butyrate is increasingly interesting because of a concern over global warming and fossil fuel shortage. Clostridium species have been long applied for the butyrate production. However, a mixture of butyrate and acetate is produced in the clostridial fermentation, which results in low selectivity of butyrate (ca. the butyrate/acetate (B/A) ratio within 10-14). To address this issue, Escherichia coli was engineered for the production of butyrate. This was carried out by pathway engineering of E. coli in a systematic way. First, the pathways leading to byproducts were removed to conserve NADH. Secondly, a heterologous pathway was constructed to direct acetyl-CoA to butyryl-CoA. Finally, endogenous atoDA was overexpressed for conversion of butyryl-CoA to butyrate at the expense of acetate. As a consequence, the resulting strain enabled production of 10 g/L butyrate from 20g/L glucose and 8 g/L acetate within 48 h. The result accounts for the B/A ratio of 143. It indicates that our approach is promising for production of butyrate in E. coli.