Scientists improved yeast's ability to grow on xylose by modifying a key enzyme. They used protein engineering and in vivo selection to enhance the enzyme's performance. By focusing on specific mutations based on crystal structures, they created two new enzyme variants that showed better growth on xylose. These mutants did not show significant changes in lab tests but performed much better in living yeast cells. The study highlights the importance of metal binding for efficient xylose conversion and suggests that optimizing this process could enhance bioethanol production.