title: Bioconversion of d-xylose to d-xylonate with Kluyveromyces lactis.
abstract: d-Xylonate was produced from d-xylose using Kluyveromyces lactis strains which expressed the gene for NADP(+)-dependent d-xylose dehydrogenase from Trichoderma reesei (xyd1). Up to 19 ± 2g d-xylonatel(-1) was produced when K. lactis expressing xyd1 was grown on 10.5 gd-galactosel(-1) and 40 g d-xylosel(-1). Intracellular accumulation of d-xylonate (up to ∼70 mg [gbiomass](-1)) was observed. d-Xylose was metabolised to d-xylonate, xylitol and biomass. Oxygen could be reduced to 6mmolO(2)l(-1)h(-1) without loss in titre or production rate, but metabolism of d-xylose and xylitol were more efficient when 12 mmolO(2)l(-1)h(-1) were provided. d-Xylose uptake was not affected by deletion of either the d-xylose reductase (XYL1) or a putative xylitol dehydrogenase encoding gene (XYL2) in xyd1 expressing strains. K. lactis xyd1ΔXYL1 did not produce extracellular xylitol and produced more d-xylonate than the xyd1 strain containing the endogenous XYL1. K. lactis xyd1ΔXYL2 produced high concentrations of xylitol and significantly less d-xylonate than the xyd1 strain with the endogenous XYL2.
authors.affiliation: VTT, Technical Research Centre of Finland, VTT Espoo, Finland. yvonne.nygard@vtt.fi
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Nygård
authors.forename: Mervi H
authors.initials: MH
authors.lastname: Toivari
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: D000429:Alcohol Oxidoreductases / Q000096:biosynthesis / Q000235:genetics; D050542:D-Xylulose Reductase / Q000096:biosynthesis / Q000235:genetics; D005656:Fungal Proteins / Q000096:biosynthesis / Q000235:genetics; D007716:Kluyveromyces / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D030781:Organisms, Genetically Modified / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D014242:Trichoderma / Q000201:enzymology / Q000235:genetics; D014993:Xylitol / Q000235:genetics / Q000378:metabolism; D014994:Xylose / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; D014994:Xylose; D000429:Alcohol Oxidoreductases; C035795:D-xylose dehydrogenase; D050542:D-Xylulose Reductase; D014993:Xylitol