초록
<P><B>Abstract</B></P> <P>Lignocellulosic-based production of bio-hydrogen (H<SUB>2</SUB>) by <I>Escherichia coli</I> requires efficient consumption of pentoses and hexoses. However, carbon catabolite repression (CCR) causes sequential utilization of carbohydrates and in some cases null consumption of less preferred carbohydrates, such as xylose. In this work, we evaluated the effect of elimination of the phosphotransferase system (PTS), responsible for CCR in strain <I>E. coli</I> WDH (Δ<I>hycA</I>) on H<SUB>2</SUB> production using mixtures of glucose-xylose as carbon source. Elimination of <I>ptsG</I> gene (glucose permease-enzyme IIB), allowed simultaneous consumption of glucose and xylose, and improved H<SUB>2</SUB> production 1.2-times with respect to the parenteral strain. Whereas, elimination of <I>ptsG</I> gene in combination with deletion of <I>ldhA</I> (<SMALL>D</SMALL>-lactate dehydrogenase) and/or <I>frdD</I> (fumarate reductase) genes, improved H<SUB>2</SUB> production 2.5-times with a H<SUB>2</SUB> yield of 0.27 mol·C-mol<SUP>−1</SUP>, using mixtures of glucose/xylose or wheat straw hydrolysate. Interestingly, besides the improvement on H<SUB>2</SUB> production, <I>E. coli</I> WDH-GFA (Δ<I>hycA,</I> Δ<I>ptsG,</I> Δ<I>frdD,</I> Δ<I>ldhA</I>) strain also produced ethanol as the main carbon by-product. These results show that elimination of <I>ptsG</I>, in combination with a modified central carbon metabolism improves the production of H<SUB>2</SUB>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The <I>ptsG</I> gene deletion promoted glucose-xylose utilization in <I>E. coli</I> WDH. </LI> <LI> The <I>ptsG</I> gene deletion improved H<SUB>2</SUB> production in <I>E. coli</I> WDH. </LI> <LI> This is first report using a mixture of glucose-xylose for H<SUB>2</SUB> production by <I>E. coli.</I> </LI> <LI> <I>E. coli</I> WDHGFA produced simultaneously ethanol-H<SUB>2</SUB> using wheat straw hydrolysate. </LI> </UL> </P>