Résumé
Substrates that contain hexose as well as pentose sugars can form an interesting substrate for the production of ethanol. Pichia stipitis and a respiratory-deficient mutant of Saccharomyces diastaticus were used to convert such a substrate into ethanol under continuous culture conditions. With a sugar mixture (glucose 70%/xylose 30%) at 50 g/l, the xylose was entirely consumed when the dilution rate (D) did not exceed 0.006 h–1 whereas the glucose was entirely consumed whatever the D. The study of influence of initial substrate concentration (S0) was performed at D = 0.015 h–1. Under these conditions the substrate was entirely consumed when its initial concentration did not exceed 20 g/l. With S0 = 80 g/l the residual xylose concentration reached 20.5 g/l. At low D or at low S0, P. stipitis was the dominant species in the fermentor. Increasing the D or S0 resulted in the wash-out of P. stipitis mainly because of its low ethanol tolerance.