In conclusion, the domestication of S. cerevisiae for carbon dioxide and ethanol formation from hexose sugars has led to the fact that the metabolism of hexose and pentose sugars in this yeast are fundamentally different. As evidenced by genome-scale transcriptome and proteome analyses of numer­ous recombinant pentose-utilizing S. cerevisiae strains, the difference is not only limited to the initial sugar conversion pathways, but also comprises the central metabolism and the glycolytic pathway. The major future challenge remains to translate the knowledge acquired from laboratory strains to indus­trial production strains.

Acknowledgements The authors acknowledge the financial support from the Swedish En­ergy Agency.