Adsorption Of Complex Cellulase On Lignin And Enhancement Of Enzymatic Hydrolysis Of Lignocelluloses

Enzymatic saccharification of lignocellulose is a crucial step in bioethanol production from lignocellulosic biomass through sugar platform which essentially requires attachment of cellulases onto cellulose.However,non-productive adsorption of cellulase onto lignin leads to high cost of cellulase in enzymatic hydrolysis of lignocellulose.In this work,the adsorption behavior of complex cellulase(CTec2)on lignin and types of interaction between cellulase-lignin were investigated by using quartz crystal microbalance(QCM-D)and polyacrylamide gel electrophoresis(SDS-PAGE).And effects of ?-glucosidase and urea on enzymatic hydrolysis of lignocellulose and their mechanisms were discussed.Effects of buffer pH,ionic strength and urea on adsorption of CTec2 on lignin film were investigated by QCM-D.The results showed that the adsorption of CTec2 on lignin increased with buffer pH increasing from 3.6 to 4.0 and then decreased with the pH exceeded 4.0.The CTec2 adsorption decreased with the increase of ionic strength when buffer pH was 4.8.It indicated that electrostatic interaction was involved in the non-productive binding of CTec2 to lignin.Besides,the adsorption of CTec2 on lignin decreased with the increase of urea concentration when buffer pH was 4.8,indicating that hydrogen bonding was one type of interaction causing non-productive binding of CTec2 and lignin.Effects of buffer pH,ionic strength,urea and surfactants on the adsorption of each component in CTec2 on lignin were investigated by SDS-PAGE.The results showed that buffer pH,ionic strength,urea and surfactants had little effects on the adsorption of ?-glucosidase(BGL)and endoglucanases(EG III and EG V)on lignin,but had significant effect on other cellulase(CBH I,CBH II,EG I,EG II,EG IV and Xyn)binding to lignin.The binding affinity of each component in CTec2 to lignin can be ranked as follows: BGL,EG III and EG V > Xyn > CBH I,CBH II,EG I,EG II and EG IV.Adsorption of BGL and EG III to lignin were little affected with the increase of urea concentration and ionic strength when buffer pH was 4.8.It suggested that hydrophobic interaction were the major causes of non-productive binding of BGL and EG III to lignin during enzymatic hydrolysis of lignocellulose.The increase of urea concentration and ionic strength could significantly reduce the adsorption of CBH I on lignin,indicating that hydrogen-bond interaction and electrostatic attraction were the dominating factors influencing the behavior.Effects of ?-CTec2(?-glucosidase in CTec2)and Novozyme 188 on the enzymatic hydrolysis of lignocellulose were investigated.The results showed that addition of Novozyme 188 had little effect on the enzymatic hydrolysis of lignocellulose,while ?-CTec2 promoted the enzymatic hydrolysis of lignocellulose.?-CTec2 had a strong adsorption on lignin,which can reduce other cellulase binding to lignin.In addition,effect of urea on the enzymatic hydrolysis of lignocellulose was also investigated.The results showed that urea with low concentration promoted lignocellulose hydrolysis,which was attributed to the decrease of CTec2 binding to lignin in the presence of urea.This work focused on types of interaction between cellulase-lignin and the possible strategies to overcome it so as to allow maximum cellulases for cellulase-cellulose productive binding.By inhibiting cellulase-lignin binding,the cellulase dosage could be reduced dramatically thereby reducing the cost of enzyme in bioethanol process.