The use of ethanol, particularly biomass-derived ethanol, can produce significant savings in carbon dioxide emissions. A two-stage bioreactor with cell recycle was developed; it is composed by two reactors with a external cell recycling loop. The first reactor dedicated to the growth reaction, second reactor (R2) was coupled to an ultrafiltration membrane in order to reach high cell concentration and/or high ethanol concentration.  Saccharomyces cerevisiae CBS8066 yeast strain was used. Fed batch cultures were carried out at 30°C and pH controlled at 4 with addition of a 14%(v/v) NH₃ solution until the micro organism reached 50% of viability and 100g/L of produced ethanol concentration. This broth was used to inoculate bioreactors (10%(v/v)) containing mineral media with an initial glucose concentration of 100gL^-1 and various initial concentrations of added ethanol (0, 38, 67, 88, 106g.L^-1). The cultures were carried out first in batch mode until the substrate was depleted and then switched into a fed-batch mode.  The impact of the initial ethanol concentration on the dynamic behaviour of S. cerevisiae was studied. This study showed that the yeast response to the stress conditions was a function of the initial cell viability and the ethanol concentration both in the inoculum and in the fermentative medium.