The Study On The Fermentation Of Hemicellulose From Wheat Straw To Produce Xylitol

The Wheat straw has very cheap price and renewable characteristic.The wheat straw was used in the hemicellulose hydrolysis extraction of xylose and the hydrolyzater was used in production of xylitol the.This process compared with the process of traditional catalytic hydrogenation production of xylitol and that has low raw material costs,mild reaction conditions,product quality and other advantages.In this article,it explore the hydrolysis of xylose in wheat straw and activated carbon adsorption the hydrolyzate.The main research results are as follows:The xylose dissolution variations of wheat straw stalks sulfuric acid hydrolysis were explored under different conditions,which demonstrated that in heat preservation temperature 120 ?,holding time 60 min,sulfuric acid concentration of 4%,the xylose extraction efficiency of wheatgrass reached the maximum amount of 0.20 g/g.Moreover,xylose dissolution process could be divided into three stages with enhancement of the hydrolysis reaction strength.X-Ray Diffraction(XRD),Fourier Transform Infrared Spectroscopy(FTIR)and Environmental Scanning Electron Microscopy(SEM)analyses confirmed that sulfuric acid concentration and temperature of heat preservation were the main factors to damage wheat straw fiber crystallization area.When the xylose extraction efficiency was maximizing,hemicellulose was almost completely degraded and dissolved.In order to Explore the product change in the process of wheat straw autohydrolysis,Ion chromatography and high performance liquid chromatography(HPLC)were used to detect sugar(arabinose,galactose,glucose and xylose)and fermentation inhibitor(formic acid,acetic acid,5-HMF and furfural)in the hydrolysate,the change rule of sugars and fermentation inhibitor in the single factor experiment have been analyzed.Liquid ratio,temperature and time parameters which have impact on xylose generation in the auto-hydrolysate were researched through the response surface analysis.And mathematical model of quadratic polynomial of xylose extraction was built.The results showed that the optimum conditions(liquid ratio1:11.67,time 57.76 min and temperature 173.93?),the xylose extraction efficiency of wheatgrass was 83.91 mg/g.After the modification,it was found by BET specific surface area analyzer and infrared spectrophotometer that the surface of the activated carbon chemical group and the pore diameter will be a certain change,and the adsorption of 5-HMF and furfuralon activated carbon at 100 mg/g of material concentration and 2.5 g/L of the amount of activated carbon can reach 89.0% and 81.0% at 20?,respectively.While the adsorption of formic acid and acetic acid is not good.In the same conditions,it can only reach 14.0% and 13.8%.And the adsorption process of 5-HMF and furfural on activated carbon belongs to the exothermic physical adsorption process and the entropy reduction process.Adsorption is most suitable for low temperature.The adsorption capacity of activated carbon to the fermentation inhibitor in hydrolyzate of wheat straw was investigated.At the same time,the changes of the surface and pore volume of the activated carbon before and after adsorption were compared.The hydrolyzate of wheat straw was treated with activated carbon and the lignin in the hydrolyzate reaches more than 90%,the removal rate of 5-HMF and furfural reach 97% under the amount of activated carbon 10 wt%,the original pH,was stirred for 5 minutes at room temperature.And the adsorption capacity of activated carbon surface micropores was higher than that of medium pore to lignin,so should be selected high percentage of porous activated carbon to the hydrolysis solution for adsorption.This paper explored the removal of fermentation inhibitors in lime neutralization enough lime neutralization and weak-base ion-exchange resin treatment.It was found that the weakly basic ion exchange resin D301 had a good effect on the fermentation inhibitor such as acetic acid in the hydrolysate and can significantly improve the fermentation performance of the hydrolysate.After seven times of concentration,activated carbon adsorption,lime neutralization and weakly alkaline ion exchange resin D301 adsorption treatment,the yield of xylitol produced by fermentation of wheat straw hydrolysate can reach 64.4%.