title: Microbial D-xylonate production.
abstract: D-Xylonic acid is a versatile platform chemical with reported applications as complexing agent or chelator, in dispersal of concrete, and as a precursor for compounds such as co-polyamides, polyesters, hydrogels and 1,2,4-butanetriol. With increasing glucose prices, D-xylonic acid may provide a cheap, non-food derived alternative for gluconic acid, which is widely used (about 80 kton/year) in pharmaceuticals, food products, solvents, adhesives, dyes, paints and polishes. Large-scale production has not been developed, reflecting the current limited market for D-xylonate. D-Xylonic acid occurs naturally, being formed in the first step of oxidative metabolism of D-xylose by some archaea and bacteria via the action of D-xylose or D-glucose dehydrogenases. High extracellular concentrations of D-xylonate have been reported for various bacteria, in particular Gluconobacter oxydans and Pseudomonas putida. High yields of D-xylonate from D-xylose make G. oxydans an attractive choice for biotechnical production. G. oxydans is able to produce D-xylonate directly from plant biomass hydrolysates, but rates and yields are reduced because of sensitivity to hydrolysate inhibitors. Recently, D-xylonate has been produced by the genetically modified bacterium Escherichia coli and yeast Saccharomyces cerevisiae and Kluyveromyces lactis. Expression of NAD(+)-dependent D-xylose dehydrogenase of Caulobacter crescentus in either E. coli or in a robust, hydrolysate-tolerant, industrial Saccharomyces cerevisiae strain has resulted in D-xylonate titres, which are comparable to those seen with G. oxydans, at a volumetric rate approximately 30% of that observed with G. oxydans. With further development, genetically modified microbes may soon provide an alternative for production of D-xylonate at industrial scale.
authors.affiliation: VTT, Technical Research Centre of Finland, P.O. Box 1000, 02044 VTT Espoo, Finland. mervi.toivari@vtt.fi
authors.forename: Mervi H
authors.initials: MH
authors.lastname: Toivari
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Nygård
authors.forename: Merja
authors.initials: M
authors.lastname: Penttilä
authors.forename: Laura
authors.initials: L
authors.lastname: Ruohonen
authors.forename: Marilyn G
authors.initials: MG
authors.lastname: Wiebe
mesh_terms: D001105:Archaea / Q000235:genetics / Q000378:metabolism*; D001419:Bacteria / Q000235:genetics / Q000378:metabolism*; D060847:Metabolic Engineering; D053858:Metabolic Networks and Pathways / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D013400:Sugar Acids / Q000378:metabolism*; D014994:Xylose / Q000378:metabolism
chemical_list: D013400:Sugar Acids; D014994:Xylose