Study On The Mechanism Of Cellulase Hydrolysis Promoted By Lignin Assembly

In this paper,for the structural heterogeneity of residual lignin in pretreated materials,the residual lignin was fractionally separated to systematically study the physicochemical properties of different lignin components(ethanol lignin and bulk lignin),chemical structure characteristics,and their differential effects on cellulase hydrolysis.The results provide an important method for studying the structure-activity relationship of lignin on the hydrolysis of cellulase.The lignin component was separated by ethanol pretreatment of sawdust as substrate.The results showed that the weight average molecular weight of the ethanol lignin(1665~1902 Da)obtained by the separation was significantly lower than that of the bulk lignin(6969~8332 Da).The content of ?-O-4 aryl ether bond in ethanol lignin(3.22~3.23/100Ar)is much lower than bulk lignin(13.70~14.46/100Ar).Simultaneously,the condensation type resin alcohol?-?structure and phenyl coumarin full ?-5 structure content of bulk lignin are lower than the bulk lignin.It is indicated that the degree of depolymerization of ethanol lignin is higher than bulk lignin.ethanol lignin and bulk lignin represent two different lignin components in ethanol pretreated sawdust.The ethanol lignin was removed by ethanol washing,which reduced the glucose yield of the ethanol pretreatment material by 15.03~15.17%,the sodium chlorite delignification method was used to remove bulk lignin,so that the 72 h glucose was obtained,the rate has increased significantly to 64.65 to 81.42%.It is indicated that the ethanol lignin in ethanol pretreatment sawdust can promote the hydrolysis of cellulase,and the bulk lignin has a strong inhibitory effect on cellulase hydrolysis.The adsorption behavior of cellulase on the surface of ethanol and bulk lignin films were monitored by quartz crystal microbalance technology in real time.The results showed that the maximum adsorption capacity of ethanol lignin cellulase was 152.63~168.09ng/cm~2,significantly lower than the bulk lignin(196.71~224.73 ng/cm~2).In addition,cellulase adsorption experiments of combined lignin films showed that the presence of ethanol lignin reduced the irreversible adsorption capacity of cellulase on the bulk lignin film by 39.2-45.0%.Therefore,it reveals the potential promoting mechanism of ethanol lignin on the hydrolysis of cellulase,that is,the ethanol lignin and the bulk lignin are assembled to each other,thereby masking the inactive adsorption site of bulk lignin to cellulase,effectively alleviating the irreversible adsorption of the enzyme on the bulk lignin.The addition of 2-naphthol and 2-naphthol-7-sulfonate in the process of pretreatment of sawdust with dilute acid increased the glucose yield of the dilute acid pretreatment material by9.1%and 47.8%,respectively.The addition of sodium 2-naphthol-7-sulfonate during pretreatment is more effective in promoting cellulase hydrolysis than 2-naphthol.The characterization of the pretreated materials showed that the addition of sodium2-naphthol-7-sulfonate significantly improved the accessibility of the material cellulose and the surface electronegativity of the material,while reducing the adsorption capacity of the pretreatment material and cellulase.In addition,lignin structural characterization experiments show that the 2-naphthol-7-sulfonate assisted pretreatment not only significantly enhances the cleavage of ?-O-4 and ?-?bonds,but also alleviates the polycondensation of lignin.Therefore,the addition of 2-naphthol derivatives during the pretreatment can improve the enzymatic hydrolysis performance of the pretreated materials by regulating the polycondensation and depolymerization of lignin.