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Everyone loves an underdog: metabolic engineering of the xylose oxidative pathway in recombinant microorganisms

Valdehuesa, Kris Niño G., Ramos, Kristine Rose M., Nisola, Grace M., Bañares, Angelo B., Cabulong, Rhudith B., Lee, Won-Keun, Liu, Huaiwei, Chung, Wook-Jin
Applied microbiology and biotechnology 2018 v.102 no.18 pp. 7703-7716
Caulobacter crescentus, Corynebacterium glutamicum, Escherichia coli, Haloferax volcanii, Saccharomyces cerevisiae, alpha-ketoglutaric acid, bacteria, byproducts, glycols, host strains, metabolic engineering, oxidation, pyruvic acid, xylose
The D-xylose oxidative pathway (XOP) has recently been employed in several recombinant microorganisms for growth or for the production of several valuable compounds. The XOP is initiated by D-xylose oxidation to D-xylonolactone, which is then hydrolyzed into D-xylonic acid. D-Xylonic acid is then dehydrated to form 2-keto-3-deoxy-D-xylonic acid, which may be further dehydrated then oxidized into α-ketoglutarate or undergo aldol cleavage to form pyruvate and glycolaldehyde. This review introduces a brief discussion about XOP and its discovery in bacteria and archaea, such as Caulobacter crescentus and Haloferax volcanii. Furthermore, the current advances in the metabolic engineering of recombinant strains employing the XOP are discussed. This includes utilization of XOP for the production of diols, triols, and short-chain organic acids in Escherichia coli, Saccharomyces cerevisiae, and Corynebacterium glutamicum. Improving the D-xylose uptake, growth yields, and product titer through several metabolic engineering techniques bring some of these recombinant strains close to industrial viability. However, more developments are still needed to optimize the XOP pathway in the host strains, particularly in the minimization of by-product formation.