FIG. 1.

Evolution of S. cerevisiae TMB3001 in carbon-limited chemostat cultures at a D of 0.05 h⁻¹ under aerobic conditions with 5 g of xylose per liter and 1 g of glucose per liter (A); under aerobic, microaerobic (light gray background), and anaerobic (dark gray background) conditions with 5 g of xylose per liter (B); and under anaerobic conditions with 5 g of xylose per liter (C). Arrow 1 indicates the time when the airflow was reduced from 0.3 liters min⁻¹ to <1 ml min⁻¹; arrow 2 indicates the time when the airflow was shut off; and arrow 3 indicates the time when anaerobiosis was initiated by sparging with technical N₂. The evolving population was subjected to EMS mutagenesis prior to inoculation of the chemostats.