Xylitol formation by Candida guilliermondii grown in a sugar cane bagasse hemicellulosic hydrolysate: Effect of aeration and inoculum adaptation

The xylose conversion into xylitol by Candida guilliermondii was evaluated in sugar cane bagasse hemicellulosic hydrolysate. The effect of air flow rates of 0.4, 0.6 and 0.8 vvm on xylitol formation was studied. In addition, inoculum previously adapted to the hydrolysate was also tested in the fermentation carried out at 0.6 vvm. The results showed that xylitol production depends markedly on the aeration rate and on the previous adaptation of the yeast to the hydrolysate. When the fermentations were carried out at an air flow rate of 0.8 vvm and non-adapted inoculum was used, the highest productivity of xylitol was 0.39 g/l x h. However, during the fermentation carried out at an air flow rate of 0.6 vvm with adapted inoculum, the productivity increased to 0.65 g/l x h. Furthermore, the adapted cells performed quite well in the presence of acetic acid concentrations of about 4.5 g/l in the medium.