title: Effect of glucose on xylose utilization in Saccharomyces cerevisiae harboring the xylose reductase gene.
abstract: We have constructed recombinant Saccharomyces cerevisiae JH1 harboring a xylose reductase gene (xyl1) isolated from Pichia stipitis. However, JH1 still utilizes glucose more easily than xylose. Therefore, in this study, we characterized the effect of a glucose supplement on xylose utilization, the expression level of xylose reductase as a recombinant gene in JH1, and the expression levels of two hexose transporters (Hxt4 and Hxt7) due to co-fermentation of different concentrations of glucose and xylose. Co-fermentation using 20 g/l of glucose increased xylose consumption up to 11.7 g/l, which was 7.9-fold that of xylose fermentation without a glucose supplement. In addition, we found xyl1 mRNA levels dramatically increased as cells grew under co-fermentation conditions with supplementary glucose; this result is consistent with a significant decrease in the xylose concentration 48 h after cultivation. In addition, the expression levels of Hxt4 and Hxt7 were strongly activated by the presence of glucose and xylose; in particular, Hxt7 showed a 2.9-fold increased expression relative to that of recombinant S. cerevisiae JHM with only a backbone vector, pYES2. The results of this study suggest that xylose utilization would be improved by activation of hexose transporters induced by glucose (rather than xylose) reductase expression.
authors.affiliation: Graduate School of Semiconductor and Chemical Engineering, Chonbuk National University, Jeonju, South Korea.
authors.forename: Ji-Hye
authors.initials: JH
authors.lastname: Han
authors.forename: Ju-Yong
authors.initials: JY
authors.lastname: Park
authors.forename: Kye Sang
authors.initials: KS
authors.lastname: Yoo
authors.forename: Hyun Woo
authors.initials: HW
authors.lastname: Kang
authors.forename: Gi-Wook
authors.initials: GW
authors.lastname: Choi
authors.forename: Bong-Woo
authors.initials: BW
authors.lastname: Chung
authors.forename: Jiho
authors.initials: J
authors.lastname: Min
mesh_terms: D000449:Aldehyde Reductase / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D005285:Fermentation; D005800:Genes, Fungal; D005947:Glucose / Q000378:metabolism*; D051246:Glucose Transport Proteins, Facilitative / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000378:metabolism; D010843:Pichia / Q000201:enzymology / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D014170:Transformation, Genetic; D014994:Xylose / Q000378:metabolism*
chemical_list: D051246:Glucose Transport Proteins, Facilitative; C090593:HXT4 protein, S cerevisiae; C095258:HXT7 protein, S cerevisiae; D009004:Monosaccharide Transport Proteins; D029701:Saccharomyces cerevisiae Proteins; D014994:Xylose; D000449:Aldehyde Reductase; D005947:Glucose