초록
<P><B>Abstract</B></P> <P>Microbial production of butanol by solventogenic <I>Clostridium</I> has long been complicated with the formation of acetone as an unwanted product, which causes poor product yields and creates a most important problem concerning substrate transformation. Intensive attempts concentrate on carbon conversion pathways to eliminate acetone, but have actually achieved little so far. Here, we believe microbial product distribution can largely depend on how the cell plays its energetic cofactors in central metabolism, and demonstrate that by introducing a synthetic 2,3-butanediol synthesis pathway in <I>Clostridium acetobutylicum</I> as an NADH-compensating module to readjust the reducing power at a systems level, the production of acetone can be selectively and efficiently eliminated (< 0.3 g/L). H<SUB>2</SUB> evolution was reduced by 78%, and the total alcohol yield was strikingly increased by 19% to 0.44 g/g glucose, much higher than those yet reported for butanol fermentation. These findings highlight that it is the loss of reducing power rather than typically manipulated solventogenesis genes that dominates acetone formation. Further study revealed that the NADH-module triggered apparent regulation of pathways involved in electron transfer and reducing power conservation. The study also suggested the key to conservation of intracellular reducing power might essentially lie in the intermediate processes in central metabolism that are related to redox partners, butyrate or C<SUB>4</SUB> branches, and possibly NADH and NADPH specificity. This study represents the first effective redox-based configuration of <I>C. acetobutylicum</I> and provides valuable understandings for redox engineering of native <I>Clostridium</I> species towards advanced production of biofuels and alcohols.</P> <P><B>Highlights</B></P> <P> <UL> <LI> An NADH-compensating module was constructed in <I>Clostridium acetobutylicum</I>. </LI> <LI> The module triggered apparent conservation of intracellular reducing power. </LI> <LI> Acetone was efficiently eliminated, giving the highest solvent yield ever reported. </LI> <LI> Reducing power rather than solventogenesis genes dominate acetone formation. </LI> <LI> Molecular basis involved redox partners, C4-metabolism and cofactor specificity. </LI> </UL> </P>