Efficient production of L-glutamic acid from xylose by a novel metabolic pathway in Corynebacterium glutamicum

We have been constructing an environmentally conscious production process of L-glutamic acid using sugars derived from lignocellulosic biomass as main carbon sources.  Hydrolysates of the biomass mainly contain glucose and xylose, however native C. glutamicum cannot originally utilize xylose due to lack of xylose isomerase (XI).  Therefore we tried to construct a new C. glutamicum strain capable of efficient utilization of xylose as well as glucose, by introduction of a novel metabolic pathway.  For the purpose, we employed Weimberg pathway in which xylose is converted into α-ketoglutarate (a precursor of L-glutamic acid) through five enzymatic reactions without carbon loss from the substrate.  The recombinant C. glutamicum introduced the xyl-operon from Caulobacter crescentus was able to grow on xylose as a sole carbon source, indicating that the heterologous oxidative xylose metabolism was functionally active in vivo.  However the strain accumulated xylonate exclusively under the biotin limited condition for induction of L-glutamic acid overproduction.  Since it was indicated that activity of xylonate dehydratase (XylD) in the introduced pathway is insufficient, we amplified xylD gene dosage in the strain.  As a result, the recombinant strain could produce L-glutamic acid efficiently from xylose.  In addition, it was indicated that the productivity of L-glutamic acid by the strain was higher than that by a strain introduced a gene encoding XI by which C. glutamicum could utilize xylose.  In this presentation, we will indicate the availability of this new strain for L-glutamic acid overproduction from biomass-derived sugars.