초록
<P><B>ABSTRACT</B></P><P>Butanol biosynthesis through aldehyde/alcohol dehydrogenase (<I>adhE2</I>) is usually limited by NADH availability, resulting in low butanol titer, yield, and productivity. To alleviate this limitation and improve n‐butanol production by <I>Clostridium tyrobutyricum</I> Δ<I>ack</I>–<I>adhE2</I> overexpressing <I>adhE2</I>, the NADH availability was increased by using methyl viologen (MV) as an artificial electron carrier to divert electrons from ferredoxin normally used for H<SUB>2</SUB> production. In the batch fermentation with the addition of 500 μM MV, H<SUB>2</SUB>, acetate, and butyrate production was reduced by more than 80–90%, while butanol production increased more than 40% to 14.5 g/L. Metabolic flux analysis revealed that butanol production increased in the fermentation with MV because of increased NADH availability as a result of reduced H<SUB>2</SUB> production. Furthermore, continuous butanol production of ∼55 g/L with a high yield of ∼0.33 g/g glucose and extremely low ethanol, acetate, and butyrate production was obtained in fed‐batch fermentation with gas stripping for in situ butanol recovery. This study demonstrated a stable and reliable process for high‐yield and high‐titer n‐butanol production by metabolically engineered <I>C. tyrobutyricum</I> by applying MV as an electron carrier to increase butanol biosynthesis. Biotechnol. Bioeng. 2015;112: 705–715. © 2014 Wiley Periodicals, Inc.</P>