Transcriptional reprograming for improved xylose metabolism in engineered yeast

Glucose repression in Saccharomyces cerevisiae has been extensively studied and well established. However, it is unknown how the native regulatory systems would respond and function if foreign metabolic pathways were introduced. In particular, the dynamics of regulatory networks in S. cerevisiae engineered for xylose metabolism have not been systematically investigated.

We first hypothesized that native transcriptional regulation of S. cerevisiae, which is optimized for glucose metabolism might limit the xylose metabolism. To test this, we perturbed key transcriptional regulators involved in regulation of sugar metabolism. We found that the deletion of a transcriptional regulator in xylose-fermenting S. cerevisiae improved the rate and efficiency of xylose fermentation. To further optimize both glucose and xylose fermentation rates, we screened mutant alleles of the transcriptional regulator. Lastly, we measured expression levels of key metabolic enzymes in glycolysis and the pentose phosphate pathway to capture the pattern of transcriptional changes after perturbation of the transcriptional regulator.

In conclusion, the perturbations of the transcriptional regulator altered transcriptional profiles in favor of xylose metabolism, and improved xylose fermentation capability. These results suggest that the native regulatory mechanisms, primarily the transcriptional regulations, might be associated with the suboptimal xylose fermentation by xylose-fermenting S. cerevisiae.