The Changes Of Corn Strover’s Main Componential Structure And Enzymelysis After Being Pretreated By Ethanol

In recent years, extensive attention has been aroused by energy and environment problems. It can be regarded as a development tendency of clean energy to produce cellulosic ethanol from agricultural wastes. It makes contribution to environment and can sovle the problem of energy shortage. The lignin that exists in the wood fiber raw material has an effect on the digestion process of cellulosic ethanol production. It will restrict the development of cellulosic ethanol. Therefore, an in-depth study on lignin is indispensable. It can provide theoretical basis for the development of cellulosic ethanol if the law of enzymolysis has been grasped.In this paper, corn stover was selected as raw material and ethanol was used to pretreat it. The results showed that during pretreatment 66.62% lignin and 61.30% extractive were removed, part of cellulose and hemicellulose were also degraded. Then hemicellulose was extracted and purified from corn stover before and after ethanol pretreatment respectively. FTIR spectrum, UV spectrum and liquid chromatogram were used to analyze the characteristic of hemicellulose. According to the results, hemicellulose from corn stover was composed mainly with xylan, with little amount of glucan, glactan and arabinan. In the process of ethanol pretreatment, glucose from hemicellulose was the easiest to be degraded, then were arabinose and galactose, xylose was the most stable. Sugar would not be oxidized to uronic acid in the mild pretreatment conditions. In addition, a decrease in molecular weight of hemicelluloses was the result of the bond breaking of part of the hemicelluloses during pretreatment.Firstly, the effect of pretreatment on lignin has been studied, milled wood lignin(MWL) and cellulytic enzyme ilignin(CEL) was extracted and purified from corn stover before and after ethanol pretreatment respectively. FTIR spectrum, UV spectrum and liquid chromatogram were used to analyze the characteristic of lignin. According to the results, it was concluded that lignin from corn stover consisted mainly of Guaiacyl, Syringyl and Hydroxyl Phenyl. In the process of ethanol pretreatment, the rand-size relationship of lignin’s degradation is as follows: G>S>H.Secondly, in order to study the resource utilization of the lignin extracted from pretreating solution, the lignin sample was grade and taken an antioxidant experiment. According to the results, it was concluded that the lower molecular weight of lignin equated to better performance of inoxidizability. Moreover, the concentration of lignin has a linear relation with the inoxidizability of lignin. That is to say, the higher the concentration is the better performance of inoxidizability.Last, the effect of lignin on enzymolysis has been studied, the lignin that extracted from corn stover before and after ethanol pretreatment was adsorbed by cellulose respectively, than measure the enzyme activity of each group. According to the results, it was concluded that the lignin extracted from corn stover after ethanol pretreatment absorbed more cellulose than the lignin in raw corn stover, had a stronger inhibitory effect of enzyme activity. Thereinto, Xylanase activity was the most inhibited, then were circumscribed glucan enzyme activity and cut inside glucan enzyme activity, β-glycosidase enzyme activity was the weakest inhibited. Otherwise, the higher protein content of cellulose, the easier to be absorbed by lignin. It will result in more decline of enzyme activity.