Xylitol production from non-detoxified corncob hemicellulose acid hydrolysate by Candida tropicalis

• Corncob hemicellulose hydrolysate without detoxification was used for xylitol production.
• Xylitol yield was influenced by the initial xylose and inhibitors concentrations in the medium.
• Biomass growth rate is essential for xylitol production.
• A maximal 38.8 g l−1 xylitol was obtained using substrate feeding strategy.

The interest on use of lignocellulose for producing chemicals is increasing as these feedstocks are low cost, renewable and widespread sources of sugars. Corncob is an attractive raw material for xylitol production due to its high content of xylan. In this study, hemicellulose hydrolysate from corncobs without detoxification was used for xylitol production by Candida tropicalis CCTCC M2012462. Compared with prepared xylose medium, xylitol production with dilute acid hydrolysate medium does not seem to influence specific xylose reductase activity. The decrease in xylitol productivity with dilute acid hydrolysate medium is a result of a lower biomass concentration and lag-phase time. It appears that biomass growth rate is essential for xylitol production. In xylitol fermentation with a low initial inhibitors concentration and substrate feeding strategy, a maximal xylitol concentration of 38.8 g l−1 was obtained after 84 h of fermentation, giving a yield of 0.7 g g−1 xylose and a productivity of 0.46 g l−1 h−1.