Abstract: Study on continuous fermentation of xylose/glucose mixture by Pichia stipitis under oxygen-limited condition to prepare ethanol was carried out. Mixture of 15.0 g/L xylose and 30.0 g/L glucose as substitute of lignocellulosic hydrolyzate, was used as main fermentation substrate. Tow-stage fermentation cultures were carried out in a two-reactor system under condition of temperature of 35℃ and a ventilation rate of 100-150 mL/min. The working volume of single reactor was 1.5 L. When the influent rate was ca. 60 mL/h, average ethanol concentration in the effluent was 13.79 g/L, and the utilization rate of reducing sugar was 83.09%. When the influent rate was changed to ca. 45 mL/h average ethanol concentration in the effluent was 15.41 g/L, and the utilization rate of reducing-sugar was 90.38%. Using immobilization and low pH value treatment method, the system was run steadily and no contamination was found during a 35-day research.

Key words: Pichia stipitis, immobilization, low pH value treatment, continuous fermentation, ethanol