Study On Corn Straw Hydrolysate Detoxification Acid Fermentation Of Xylitol

Xylitol is a highly value-added product. Its domestic and international market demand is increasing. The hydrolysis product of hemicellulose is rich in xylose which can be converted into xylitol through a chemical reaction or bio-fermentation. Recent studies show that bio-fermentation which acting under mild conditions is the best method to produce xylitol in industrial and it does not need high-grade purity of xylose solution as raw materials. During the hydrolytic process of hemicellulose, some assistant production which was toxic to microorganism was produced. Thus further exploration of xylitol at commercial scale was restricted.This paper studies on the process optimization of corn straw hydrolysis catalyzed by solid acid ZSM-5 and the detoxification technology in xylitol production such as organic solvent extraction, D311 resin adsorption, excessive alkali combines organic solvents, excessive alkali combines D311 resin adsorption. By detecting the removal rate of the major inhibitor of the treated hydrolyzate and the loss rate of xylose, it is sure that excessive alkaline combines D311 anion resin adsorption is the best detoxification methods.Solid acid ZSM-5 was used to catalytic hydrolyzed the hemicellulose of corn straw. The effects of retention time, temperature, concentration of catalyst, the ratio of liquid to solid were analyzed by means of orthogonal test. The optimal condition of hydrolysis of corn straw with was concentration of catalyst 20%, ratio of liquid to solid 10:1,140℃ for 240 min. The yield of xylose could achieve to 66.2%(xylose/pentosane) under the optimal condition of hydrolysis.The removal rate of the main inhibitors such as acetic acid, furfural increased by more than 15% when the hydrolysate treated by excessive alkaline combines solvent extraction or D311 anion resin adsorption detoxification. Especially, the excessive NaOH combines D311 anion resin adsorption detoxification led to removal rate of 95.16% of furfural, but at the same time, led to the highest loss rate of xylose 21.59%.To further verify the detoxification effect, the hydrolysate treated by the best detoxification method was placed in 250 mL cone-shaped bottles, fermented by Candida, tropicalis and the yield of xylitol after 72 hours reached to 52.31%..All the hydrolysate solution prepared by different detoxification methods were fermented under the best conditions of fermentation.By comparing the fermentation efficiency and overall economic benefit addition with the costs and environmental impact analysis, the excessive alkaline combines D311 anion resin adsorption detoxification is determined to be feasible.