Fermentation of sugar cane bagasse hemicellulosic hydrolysate for xylitol production: Effect of pH

Candida guilliermondii FTI 20037 was grown In sugar cane bagasse hydrolysate supplemented with (NH4)(2)SO4 2.0 g l(-1), CaCl2 0.1 g l(-1) and rice bran 20.0 g l(-1), through 45-h batch tests (agitation of 200 min(-1) and temperature of 30 degrees C) with initial pH varying from 2.5 to 7.5. Under pH < 4.5 the consumption of glucose, xylose and arabinose as well as the production of xylitol and cells were inhibited. Nevertheless, at pH values greater than or equal to 5.5 the yeast produced xylitol with a yield of 0.75 g g(-1) and productivity of 0.57 g l(-1) h(-1). Moreover, the yeast was also capable of metabolizing the acetic acid, which is always present in media made from hydrolysates of plant material. The inhibition of xylose/xylitol bioconversion could be related to the effects of low pH and undissociated acetic acid concentration over 5.0 g l(-1). (C) 1997 Published by Elsevier Science Ltd.