Fig. 2: Metabolic engineering of S. stipitis for efficient glucose/xylose co-utilization.

The SC-ura medium containing 70 g/l glucose and 40 g/l xylose was used. High concentrations of both sugars were used in HCDF considering that glucose at a regular concentration (e.g., 20 g/l) would be depleted in the first 24 h. It was therefore difficult to observe the impact of CCR on xylose assimilation. a Sugar utilization of strain Ss-WT xyl and Ss-xyl. b Screening of xylose-specific transporters cloned from different sources. Bars indicate xylose consumed and glucose remaining after the 5-day fermentation. Ss S. stipitis, WT wild type, Sp Spathaspora passalidarum, Sc Saccharomyces cerevisiae, Nc Neurospora crassa. Ss-xyl carries the engineered xylose assimilation pathway with the promoters of the five identified genes swapped with constitutive ones whereas Ss-WT xyl-SpXut1 contains the overexpressed SpXut1 transporter with the wild type xylose conversion pathway. The rest of the strains have both the overexpressed transporter and the engineered xylose assimilation pathway. Samples were collected after 120 h of cultivation. Data are presented as mean ± S.D., n = 3 per group. Statistical analysis for comparing xylose consumption was performed using a two-sided Student’s t test. Selected comparisons are shown. *p < 0.05, **p < 0.01, ***p < 0.001 versus the strain Ss-xyl. Source data are provided as a Source Data file.