초록
<P><B>Background</B></P><P>Fermentative hydrogen (H<SUB>2</SUB>) production suffers from low carbon-to-H<SUB>2</SUB> yield, to which problem, co-production of ethanol and H<SUB>2</SUB> has been proposed as a solution. For improved co-production of H<SUB>2</SUB> and ethanol, we developed <I>Escherichia coli</I> BW25113 Δ<I>hycA</I> Δ<I>hyaAB</I> Δ<I>hybBC</I> Δ<I>ldhA</I> Δ<I>frdAB</I> Δ<I>pta</I>-<I>ackA</I> Δ<I>pfkA</I> (SH8*) and overexpressed Zwf and Gnd, the key enzymes in the pentose-phosphate (PP) pathway (SH8*_ZG). However, the amount of accumulated pyruvate, which was significant (typically 0.20 mol mol<SUP>−1</SUP> glucose), reduced the co-production yield.</P><P><B>Results</B></P><P>In this study, as a means of reducing pyruvate accumulation and improving co-production of H<SUB>2</SUB> and ethanol, we developed and studied <I>E. coli</I> SH9*_ZG with functional acetate production pathway for conversion of acetyl-CoA to acetate (<I>pta</I>-<I>ackA</I><SUP>+</SUP>). Our results indicated that the presence of the acetate pathway completely eliminated pyruvate accumulation and substantially improved the co-production of H<SUB>2</SUB> and ethanol, enabling yields of 1.88 and 1.40 mol, respectively, from 1 mol glucose. These yields, significantly, are close to the theoretical maximums of 1.67 mol H<SUB>2</SUB> and 1.67 mol ethanol. To better understand the glycolytic flux distribution, glycolytic flux prediction and RT-PCR analyses were performed.</P><P><B>Conclusion</B></P><P>The presence of the acetate pathway along with activation of the PP pathway eliminated pyruvate accumulation, thereby significantly improving co-production of H<SUB>2</SUB> and ethanol. Our strategy is applicable to anaerobic production of biofuels and biochemicals, both of which processes demand high NAD(P)H.</P><P><B>Electronic supplementary material</B></P><P>The online version of this article (doi:10.1186/s13068-016-0510-5) contains supplementary material, which is available to authorized users.</P>