Researchers improved the ability of yeast to tolerate high ethanol levels by evolving them in a lab setting. They used a method called Adaptive Laboratory Evolution, where yeast were exposed to increasing ethanol concentrations over many generations. The evolved yeast populations were able to survive higher ethanol levels and ferment glucose faster, producing more ethanol than the original strains. One of the evolved populations also showed an increase in growth rate. This study demonstrates that yeast can be adapted to better handle stressful conditions like high ethanol levels, which is important for industries like bioethanol production.