title: The glucose/xylose facilitator Gxf1 from Candida intermedia expressed in a xylose-fermenting industrial strain of Saccharomyces cerevisiae increases xylose uptake in SSCF of wheat straw.
abstract: Ethanolic fermentation of lignocellulose raw materials requires industrial xylose-fermenting strains capable of complete and efficient D-xylose consumption. A central question in xylose fermentation by Saccharomyces cerevisiae engineered for xylose fermentation is to improve the xylose uptake. In the current study, the glucose/xylose facilitator Gxf1 from Candida intermedia, was expressed in three different xylose-fermenting S. cerevisiae strains of industrial origin. The in vivo effect on aerobic xylose growth and the initial xylose uptake rate were assessed. The expression of Gxf1 resulted in enhanced aerobic xylose growth only for the TMB3400 based strain. It displayed more than a 2-fold higher affinity for D-xylose than the parental strain and approximately 2-fold higher initial specific growth rate at 4 g/L D-xylose. Enhanced xylose consumption was furthermore observed when the GXF1-strain was assessed in simultaneous saccharification and co-fermentation (SSCF) of pretreated wheat straw. However, the ethanol yield remained unchanged due to increased by-product formation. Metabolic flux analysis suggested that the expression of the Gxf1 transporter had shifted the control of xylose catabolism from transport to the NAD(+) dependent oxidation of xylitol to xylulose.
authors: Centro de Recursos Microbiológicos (CREM), Departamento de Ciências da Vida, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal.
authors: César
authors: C
authors: Fonseca
authors: Kim
authors: K
authors: Olofsson
authors: Carla
authors: C
authors: Ferreira
authors: David
authors: D
authors: Runquist
authors: Luís L
authors: LL
authors: Fonseca
authors: Bärbel
authors: B
authors: Hahn-Hägerdal
authors: Gunnar
authors: G
authors: Lidén
mesh_terms: D000332:Aerobiosis; D000693:Anaerobiosis; D001692:Biological Transport; D002175:Candida / Q000201:enzymology / Q000235:genetics*; D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D005800:Genes, Fungal; D007218:Industrial Microbiology / Q000379:methods; D009243:NAD / Q000378:metabolism; D010084:Oxidation-Reduction; D018547:Plant Stems; D010957:Plasmids / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000254:growth & development; D013045:Species Specificity; D014908:Triticum; D014993:Xylitol / Q000378:metabolism; D014994:Xylose / Q000378:metabolism*; D014996:Xylulose / Q000378:metabolism
chemical_list: D005656:Fungal Proteins; D011993:Recombinant Fusion Proteins; D009243:NAD; D000431:Ethanol; D014996:Xylulose; D014994:Xylose; D014993:Xylitol