For the production of xylitol using hemicellulosic hydrolysates,the process is affected by the sugar concentration in the fermetation medium and the ratio in which they occur, and also by the toxic compounds released during hemicellulose hydrolysis. Forexample, high concentrations of monomeric sugars may causeosmotic stress and incite ethanol production by the yeast in into lerable concentrations [35]. C. tropicalis ATCC 96745 was grown ina synthetic medium containing 60 g L−1of xylose and in differentconcentrations of glucose, and it was observed that glucose stronglyinhibited the formation of xylitol at all levels. Initial low glucose