Effects Of Pretreatment On The Fermentation Of Fermentable Sugars From Bamboos And The Adsorption Of Cellulase On Substrates

Bamboo,which is rich in cellulose and hemicellulose,is an important potential raw material for the production of fermentable sugars.It is an effective method to improve the utilization rate of bamboo to produce fermentable sugar by enzymatic hydrolysis and saccharification,which can be used to produce fuel ethanol.Two-stage pretreatment is a combination of two pretreatment methods to improve the efficiency of enzymatic hydrolysis and saccharification by changing the physical and chemical properties of lignocellulose surface.In this paper,a two-stage pretreatment method of hot water and green liquid was used to pretreat bamboo,which reduced the enzymatic hydrolysis barrier of bamboo,and additives were added in the enzymatic hydrolysis process to reduce the adsorption of lignin on cellulase in the substrate of enzymatic hydrolysis,and improve the yield of fermentable sugars prepared by enzymatic hydrolysis.NMR and GPC were used to analyze the changes in the structure,functional groups and molecular weight of lignin before and after pretreatment,and a single-component lignin membrane sensor and a two-component lignin-cellulose membrane sensor were constructed.QCM-D was used to study the adsorption kinetics model of cellulase by the membrane sensor.The results show that:1.The two-stage pretreatment of hot water（HW）and green liquor（GL）could destroy the dense structure of bamboo.Under the optimal pretreatment condition（HW1+GL4）,the lignin removal rate was 63.00%and cellulose retention rate was 58.93%.XRD and XPS analysis showed that the crystallinity of bamboo was improved and the surface lignin content was decreased.2.The enzymatic hydrolysis efficiency of bamboo solid pretreated with hot water and green liquor was higher than that of bamboo solid pretreated with hot water and green liquor alone.The total sugar yield of enzymatic hydrolysis was85.51%,but the hydrolysis efficiency of hemicellulose was low.The addition of bovine serum albumin（BSA）and Tween80 can promote the enzymatic hydrolysis efficiency of hemicellulose,and the promoting efficiency of BSA is better than Tween80,and the combined action of BSA+Tween80 can increase the enzymatic hydrolysis efficiency by 22.45%.In the end,HW1+GL4 pretreatment and BSA+Tween80 compound agent combination were adopted,and the total sugar yield of enzymatic hydrolysis was 99.67%,which realized efficient enzymatic hydrolysis conversion of carbohydrates.3.Combined with elemental analysis,GPC,¹³C NMR and 2D-NMR(¹H-¹³C HSQC NMR),it was found that the carbon and oxygen elements and molecular weight of lignin were decreased,and the contents of G-type and S-type structural units were also decreased.³¹P NMR analysis showed that the total hydroxyl content of lignin in two stages of hot water-green liquor pretreatment decreased.Dissipative microcrystal balance was used to study the change of frequency and mass during the adsorption process of enzyme on MWL membrane.The results showed that increasing the concentration of cellulase would increase the adsorption amount of cellulase on single-component lignin sensor and shorten the time of adsorption equilibrium.The increase of temperature will increase the adsorption capacity of enzyme hydrolysis substrate to cellulase.The adsorption equilibrium time of lignin-cellulose two-component sensor for cellulase was shorter than that of single-component lignin,and the adsorption amount of cellulase was correspondingly reduced.The non-productive adsorption amount of lignin for cellulase was the least,which was positively correlated with the total hydroxyl content of lignin.In addition,the adsorption kinetics models of cellulase by single-component lignin membrane and two-component lignin-cellulose membrane were established under different conditions.