Resume

 Nutritional supplementation of the medium is very important in ensuring successful of the fermentation, since yeast cells require a wide range of nutrients for their growth and metabolic functions. It is also known that the nutrients required can be different depending on the yeast. Therefore, the fermentative performance of Pichia stipitis and Candida guilliermondii growth in sugarcane bagasse hydrolysate supplemented with different nutrients was evaluated. Experiments were carried out with sugarcane hemicelullosic hydrolysate supplemented with rice bran extract (an important source of vitamins and amino acids that greatly furthers the development of microorganisms), (NH₄)₂SO₄ and CaCl₂ (H1); peptone and yeast extract (H2); (NH₄)₂SO₄, CaCl₂, peptone and yeast extract (H3) and a control experiment employing non-supplemented hydrolysate (H4). Nutritional supplementation of hydrolysate favored xylose consumption, cell growth and ethanol and xylitol production by yeasts. P. stipitis produced only ethanol, while C. guilliermondii produced xylitol as the main product and ethanol and glycerol as byproducts. The maximum values of Y_P/S (0.83g/g) and Q_P (0.56g/l.h) were observed on hydrolysate H1 for xylitol by C. guilliermondii after 48h of fermentation, corresponding to a xylose to xylitol conversion efficiency of 90.5%. Maximum values of Y_P/S (0.46g/g) and Q_P (0.29g/l.h) were obtained on hydrolysate H3 for ethanol by P. stipitis after 48h of fermentation, corresponding to a xylose to ethanol efficiency conversion of 92%.