초록
<P><B>Abstract</B></P><P><B>BACKGROUND</B></P><P>Ethanologenic <I>Escherichia coli</I> KO11 was modified to channel carbon flux from glucose through the Entner–Doudoroff (ED‐P) and pentose phosphate (PP‐P) pathways by using a phosphoglucose isomerase (<I>pgi</I>) knockout in the glycolytic pathway. This strain grows very slowly under non‐aerated conditions with minimal media supplemented with 4% glucose. To improve the capacity to grow, KO11 Δ<I>pgi</I> was evolved for 60 days; the resultant strain was named KO11 E35, which directs the carbon flux through the PP‐P and ED‐P to lactate and acetate production.</P><P><B>RESULTS</B></P><P>The activities of glucose‐6‐phosphate dehydrogenase and the ED‐P enzymes increased 17‐fold and 2‐fold, respectively, in KO11 E35 in comparison with KO11. A homoethanologenic derivative was constructed from KO11 E35 by deleting the <I>pta</I>, <I>ack</I> and <I>ldh</I> genes, yielding the KO11 PPAL strain. This strain channels most of the carbon flux from pyruvate to ethanol and increased expression of heterologous pyruvate decarboxylase and alcohol dehydrogenase from <I>Zymomonas mobilis</I> allowed us to obtain specific ethanol production rates similar to those found in KO11, but with half the cell mass, i.e. larger ethanol/glucose and ethanol/biomass yields.</P><P><B>CONCLUSIONS</B></P><P>These results suggest that it is possible to obtain the same carbon flux using the PP‐P and ED‐P as when using the Embden–Meyerhof–Parnas pathway for glucose catabolism to ethanol. © 2016 Society of Chemical Industry</P>