One of the main problems limiting the economic production of ethanol from lignocellulosic biomass is D-xylose fermentation. In a medium containing glucose and xylose, it is preferable to achieve conversion with glucose fermenting yeast like S. cerevisiae and xylose fermenting yeast like P. stipitis. In order to resolve this problem, it is better to use respiratory deficient mutants. In this research, respiratory deficient mutant strains S. cerevisiae V30 and Ja(a) were obtained and their ability to ferment glucose in coculture with P. stipitis was investigated. A higher xylose conversion was observed in P. stipitis cultivation with these mutants because of better oxygen conditions than in the culture with native S. cerevisiae. A degree of assimilated xylose did not efficiently increased ethanol yields but on the other hand it increased the production of yeast biomass. Process considerations in relation to the fermentative performances using different strains combinations are discussed.