Optimization of SO2 ‐catalyzed hydrolysis of corncob for xylose and xylitol production

Abstract BACKGROUND Conventional techniques for corncob hydrolysis were generally based on acid treatment. However, a large number of by‐products and undesirable compounds released during acid hydrolysis process may act as inhibitors to xylitol fermentation. To replace acid hydrolysis, SO2‐catalyzed hydrolysis was used in this study to improve the fermentability of corncob hemicellulose hydrolysate. RESULTS Based on a central composite design (CCD), 20 operations were performed to optimize the process of SO2‐catalyzed hydrolysis by varying SO2 concentration, temperature and reaction time. The optimum condition found for these parameters was 2.16% (wt), 142 °C, 98 min, with 90.51% of the theoretical xylose yield obtained. In a comparison with sulfuric acid hydrolysis, SO2‐catalyzed hydrolysis was proved to be preferable since it resulted in approximately the same sugar yields, but better fermentability. The conversion of xylose to xylitol and volumetric productivity fermented from concentrated SO2‐catalyzed hydrolysate (SCH) were 70.21% and 1.16 g L‐1 h‐1, respectively, higher than those fermented from concentrated sulfuric acid hydrolysate (SAH). CONCLUSION Findings suggested that the SO2‐catalyzed hydrolysis strategy can be conveniently and effectively applied to xylose and xylitol production. © 2013 Society of Chemical Industry