Study Of Extraction Of Hemicellulose And Enzymatic Hydrolysis To Produce Xylo-Oligosaccharides From Corn Stalk

As the most representative functional sugar,the application areas and market demands of xylo-oligosaccharides(XOS)have been expanding year by year.And as the most representative of lignocellulosic materials in China,corn stalk(CS)are huge in quantity,cheap and easy-to-obtain,which will be a great candidate to produce XOS.Owing to the complex structure of CS,XOS obtained from CS are accompanied by problems such as low purity and high color value,which degrade the product.Therefore,the refinement of XOS from CS has become the focus of this study.First of all,this study explored the effect of the organizational difference of CS on hemicellulose extraction and enzymatic hydrolysis to produce XOS.Followed by a study of removal of chromophore in enzymatic hydrolysis during the production of XOS.Finally,activated carbon adsorption conditions and ethanol gradient elution concentrations during the purification of XOS by activated charcoal-ethanol method were systematically investigated.The main conclusions were as follows:(1)In order to study the effect of the organizational difference of CS on hemicellulose extraction and enzymatic hydrolysis,CS was divided into three parts:leaf,bark and pith.After pretreatment,xylans were obtained by alkaline solution,followed by enzymatic hydrolysis.The results showed that the highest purity of xylan extracted from pith reached 84.89%,while the lowest color value was 1.43×105 and the highest hemicellulose recovery ratio was 91.03%.The enzymatic hydrolysis results revealed that the highest enzymatic hydrolysis ratio was obtained from pith at 40.09%,followed by leaf at 30.57%and bark with the worst ratio at 20%.In summary,corn pith was more conducive to the hemicellulose extraction and enzymatic hydrolysis to produce XOS.(2)In order to removal of chromophore in enzymatic hydrolysis to improve the quality of XOS from CS.Firstly,removal of chromophore in enzymatic hydrolysis by acid precipitation;then,the ethanol elution concentration was systematically investigated after optimizing the adsorption conditions.The results showed that the purity of XOS was increased by 19.97%to 87.28%,and the color value was decreased by 77.57%to 1050 when the acid precipitation pH was 2.On the basis of acid precipitation,using the optimum adsorption conditions and elution volume,the highest purity of XOS was 97.87%,with the lowest color value,780,which reached the standard of the commercial XOS.(3)In order to investigate desorption during ethanol elution to improve the quality and antioxidant activity of XOS from CS,the desorption was systematically investigated after optimizing the elution conditions.The results showed that it had an elution watershed when the volume ratio was 2:1.XOS had an obvious priorities of desorption during ethanol gradient elution.The highest purity of XOS was 98.12%from 30%ethanol eluate.Antioxidant activity assay showed that the highest radical scavenging activity of XOS was 89.89%obtained from 70%ethanol eluate at a concentration of 3 mg/mL,which could be used in antioxidant food,feed additives.