Influence of various glucose/xylose mixtures on ethanol production by Pachysolen tannophilus

Ethanol production was experimented in different synthetic glucose/xylose mixtures by Pachysolen tannophilus1771. Glucose was the preferred substrate in fermentation on mixed sugars, xylose fermentation started after glucose was exhausted. The presence of glucose could limit the xylose consumption and there was an adaptive period for P. tannophilus to utilize xylose to produce ethanol after glucose used up in fermentation on mixed sugars. The average glucose rate (1.28 g l−1 h−1) was higher than the average xylose consumption rate (0.34 g l−1 h−1) in fermentation on single sugar. Highest ethanol concentration (6.90 g l−1) was obtained at the 12th hour of fermentation on 100% glucose, while the lowest ethanol concentration (2.70 g l−1) was obtained at the 48th hour of fermentation on 100% xylose. But biomass showed an opposite result that highest biomass (6.65 g l−1) was obtained in fermentation on pure xylose and lowest biomass (5.22 g l−1) was obtained in fermentation on pure glucose.