D-glucose-insensitive uptake of D-xylose by engineered S. cerevisiae strains. Growth of strain DS71054 (a) and DS71054 EvoB (b) on 1% D-xylose and varying D-glucose concentration: 0% (open circles), 3% (solid circles), 6% (open squares), and 10% (solid squares). (c) Uptake of 50 mM [14C-] D-xylose by the DS71054 (open circles) and DS71054 EvoB (solid circles) strains in the presence of competing concentrations of D-glucose. Growth of the DS68625 strain expressing HXT36 (open circles) or HXT36-N367I (solid circles) on 2% D-glucose (d) or 2% D-xylose/0.05% maltose (e). Growth on xylose was corrected for the slight background growth on 0.05% maltose using the DS68625 strain transformed with an empty plasmid. (f) Uptake of 50 mM [14C-] D-xylose by the DS68625 strain expressing HXT36 (open circles) or HXT36-N367I (solid circles) in the presence of various glucose concentrations. Strain DS71054 contains a xylose-fermenting pathway and lacks the hexose kinases necessary for growth on glucose, but contains a full complement of hexose transporters. This strain grows on xylose but can no longer grow on glucose. Strain DS68625 contains a xylose-fermenting pathway but lacks the HXT1-7 and GAL2 genes and therefore cannot grow on xylose, while it grows poorly on glucose.