Corn Straw Hemicellulose Hydrolyzate For Xylitol Fermentation Applications

Xylitol is functional sugar alcohol ,it can prevent dental caries,it also a sweetener for diabetics an alternative and protect liver. Industrially, xylitol is produced by chemical hydrogenation of D-Xylose into xylitol. Because the microbial fermentation production condition is easy to control and lower costs, it becomes a research hotspot. Hemicelluloses hydrolyzates contains a number of fermentation inhibiting substances, this substances need to be removed, before hydrogenation it also need a series separation and purification to get high purity products. Before microbial fermentation, so as to Improve the conversion rate of xylitol.This study we uses straw hemicellulose hydrolyzate of corn as raw materials, combined with activated carbon and ultrafiltration manner decolorization, nanofiltration desalination, after decolorization and desalting, hydrolyzate for xylitol fermentation conducted a preliminary study, the results show that:In this study, first use activated carbon removed pigment, based on single-factor test, decolorization using response surface methodology to optimize the conditions, the best conditions for decolorization: add the amount of actived carbon 27.7g/L, operating temperature is 57.92℃, operating time is 21.28min, decolorization rate is 70.9074%, and loss rate of Xylose is 7.65525%. Based on the optimization program, In order to facilitate the experiment, activated carbon dosage is 28g/L, Operating temperature is 60℃, and Operating time is 30min to experimental verification. This experiment is Repeated 5 times, get the decolorization rate is 75.892%, Loss rate of Xylose is 10.694%.Based on the active carbon ,study of the ultrafiltration pressure, temperature, time, velocity, feed concentration on the decolorization effect, determine the ultrafiltration conditions: pressure 0.1MPa, temperature 30℃, time of 30min, flow rate of 6L/h, 2 times more concentrated feed solution. Under these conditions, ultrafiltration, get the real rate of 60.532% decolorization, the loss rate of 9.049% xylose.Study the nanofiltration pressure, temperature, time, pH, concentration of the feed desalination effect, determine the nanofiltration conditions: pressure 0.6MPa, temperature 20℃, time of 40min , liquid concentrated 2 times, experimental verification rate of 70.003% after desalination.Optimized Candida tropicalis 1779 growth conditions , and in this condition, the conversion rate of xylitol is 45.62 g/L, and simulation of xylitol obtained by fermentation from the conversion of 63.91g / L difference, so the need for further study.