BACKGROUND: Xylitol, a sugar alcohol widely used in food and pharmaceutical industries, can be produced through biological reduction of xylose present in hemicellulose hydrolysates by Candida tropicalis. However, the aeration rate and by-products originating from hemicellulose hydrolysis strongly inhibit the production of xylitol in a fermentation process. A two-stage fed-batch fermentation system was developed to reduce these inhibitory effects and to improve xylitol production from corn cob hemicellulose hydrolysates by C. tropicalis. RESULTS: Results of batch fermentations indicated that high xylitol production could be obtained from C. tropicalis at an initial xylose concentration of 80 g L-1 in corn cob hydrolysate medium at an aeration rate of 0.4 vvm at the micro-aeration stage. In the two-stage fed-batch fermentation process, 96.5 g L-1 xylitol was obtained after 120 h, giving a yield of 0.83 g g(-1) and a productivity of 1.01 g L-1 h(-1), which were 12.16% and 65.57% higher than those in a batch fermentation. CONCLUSION: High xylitol production can be achieved in a two-stage fed-batch fermentation process, in which the negative effects of aeration rate and inhibitory compounds on xylitol formation can be considerably reduced. (C) 2011 Society of Chemical Industry