title: Engineering of carbon catabolite repression in recombinant xylose fermenting Saccharomyces cerevisiae.
abstract: Two xylose-fermenting glucose-derepressed Saccharomyces cerevisiae strains were constructed in order to investigate the influence of carbon catabolite repression on xylose metabolism. S. cerevisiae CPB.CR2 (Delta mig1, XYL1, XYL2, XKS1) and CPB.MBH2 (Delta mig1, Delta mig2, XYL1, XYL2, XKS1) were analysed for changes in xylose consumption rate and ethanol production rate during anaerobic batch and chemostat cultivations on a mixture of 20 g l(-1) glucose and 50 g l(-1) xylose, and their characteristics were compared to the parental strain S. cerevisiae TMB3001 ( XYL1, XYL2, XKS1). Improvement of xylose utilisation was limited during batch cultivations for the constructed strains compared to the parental strain. However, a 25% and 12% increased xylose consumption rate during chemostat cultivation was achieved for CPB.CR2 and CPB.MBH2, respectively. Furthermore, during chemostat cultivations of CPB.CR2, where the cells are assumed to grow under non-repressive conditions as they sense almost no glucose, invertase activity was lower during growth on xylose and glucose than on glucose only. The 3-fold reduction in invertase activity could only be attributed to the presence of xylose, suggesting that xylose is a repressive sugar for S. cerevisiae.
authors.affiliation: Centre for Process Biotechnology, BioCentrum-DTU, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark.
authors.forename: C
authors.initials: C
authors.lastname: Roca
authors.forename: M B
authors.initials: MB
authors.lastname: Haack
authors.forename: L
authors.initials: L
authors.lastname: Olsson
mesh_terms: D000693:Anaerobiosis; D018533:Biomass; D004268:DNA-Binding Proteins / Q000235:genetics; D000431:Ethanol / Q000378:metabolism; D005285:Fermentation; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D005947:Glucose / Q000378:metabolism*; D005990:Glycerol / Q000378:metabolism; D007700:Kinetics; D009154:Mutation; D012097:Repressor Proteins / Q000235:genetics / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000502:physiology; D014994:Xylose / Q000378:metabolism*; D043324:beta-Fructofuranosidase / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; C085976:MIG1 protein, S cerevisiae; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D000431:Ethanol; D014994:Xylose; D043324:beta-Fructofuranosidase; D005947:Glucose; D005990:Glycerol