ETHANOL-PRODUCTION FROM A MIXTURE OF GLUCOSE AND XYLOSE BY A NOVEL COCULTURE SYSTEM WITH 2 FERMENTERS AND 2 MICROFILTRATION MODULES

We developed a novel co-culture system composed of two fermenters and two microfiltration modules for efficient ethanol production from a mi xture of glucose and xylose by co-culture of Pichia stipitis and Sacch aromyces cerevisiae, In a conventional co-culture where P. stipitis an d S. cerevisiae were inoculated simultaneously into a single fermenter , it was impossible to maintain the specific oxygen uptake rate (qO(2) ) at an optimum value for ethanol production from xylose by P. stipiti s due to oxygen consumption by S. cerevisiae. The ethanol concentratio n obtained in the conventional co-culture was lower than that in a sin gle culture of P. stipitis alone in which qO(2) was adjusted to an opt imum level depending upon the kind of sugar consumed. The proposed co- culture system allowed regulation of the dissolved oxygen concentratio n at a level suitable for an individual yeast in each fermentor as wel l as the successful exchange of culture medium between two fermenters. When P. stipitis and S. cerevisiae were cultivated individually under different oxygen supply conditions in the new co-culture system, the yield and productivity of ethanol from a glucose and xylose mixture we re higher than in single culture of P. stipitis alone.