초록
<P><B>Abstract</B></P> <P>Hydrolysis of plant biomass generates a mixture of simple sugars that is particularly rich in glucose and xylose. Fermentation of the released sugars emits CO<SUB>2</SUB> as byproduct due to metabolic inefficiencies. Therefore, the ability of a microbe to simultaneously convert biomass sugars and photosynthetically fix CO<SUB>2</SUB> into target products is very desirable. In this work, the cyanobacterium, <I>Synechocystis</I> 6803, was engineered to grow on xylose in addition to glucose. Both the <I>xylA</I> (xylose isomerase) and <I>xylB</I> (xylulokinase) genes from <I>Escherichia coli</I> were required to confer xylose utilization, but a xylose-specific transporter was not required. Introduction of <I>xylAB</I> into an ethylene-producing strain increased the rate of ethylene production in the presence of xylose. Additionally, introduction of <I>xylAB</I> into a glycogen-synthesis mutant enhanced production of keto acids. Isotopic tracer studies found that nearly half of the carbon in the excreted keto acids was derived from the engineered xylose metabolism, while the remainder was derived from CO<SUB>2</SUB> fixation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A heterologous xylose assimilation pathway was introduced into a cyanobacterium. </LI> <LI> Transgenic <I>Synechocystis</I> 6803 grows on xylose in addition to glucose and CO<SUB>2</SUB>. </LI> <LI> Production of ethylene, alpha-ketoglutarate (AKG), and pyruvate is enhanced. </LI> <LI> Conversion of both xylose and CO<SUB>2</SUB> to keto acids can occur without cell growth. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>