Analysis Of Adsorption And Hydrolysis Of Cellulase Based On QCM-D

Lignocellulose is the largest and most abundant untapped biomass resources reserved in nature.It is especially significant for developing circular economy and green economy to release sugar moiety from lignocellulose using the enzymatic based biological refining technology and then synthesize liquid fuel and bio-based chemicals.In this study,we investigated the adsorption and hydrolysis behavior of two kinds of cellulase on the cellulose thin film by QCM-D,and built an adsorption kinetic model of the enzymes to provide useful reference amd accumulate data for the design of a new-type compounded cellulose system for lignocellulose hydrolysis.The main conclusions were as follows.1.Research about regulation of cellulase behavior by changing pH and using cellulase inhibitors: Cel7 A and Cel7 B would hydrolyze cellulose thin film gradually in absence of inhibitors,showing the variation tendency of frequency shift to decrease and then rise up.However,the viscoelastic properties of the thin films caused by the hydrolysis of the two cellulases were different.The energy dissipation of the films continued to rise under the hydrolysis of Cel7 A,nevertheless,Cel7 B hydrolysis led the energy dissipation of the cellulose films to increase first and then decrease.This phenomenon was caused by the different mechanisms of the two enzyme.The catalysis of cellulase was inhibited significantly in the presence of glucose and cellobiose,which was benifical for investigation of cellulase adsorption.Taking the effect of enzymatic inhibition and economic cost into account,we chose 6000 ppm glucose as the hydrolysis inhibitor of Cel7 A and 3000 ppm cellobiose as the hydrolysis inhibitor of Cel7 B.The adsorption behavior of the two cellulases rendered the obvious differences under various pH.It was beneficial for Cel7 A to adsorb under the condition of acidic pH(? 4.8),while was conductive to desorb under alkaline pH(especially under pH of 9 and 10).The condition of pH ? 4.8 benefited the adsorption of Cel7 B on Avicel and alkaline pH benefited desorption of Cel7 B,just the same as Cel7 A.2.Research about adsorption dynamics of cellulase: The adsorption of cellulase on the cellulose thin film increased first and then remained constant.The higher the cellulase concentration was,the lager adsorbing capacity on the cellulose film surface became;but when it exceeded a certain concentration,all the adsorption sites were occupied and the adsorbing capacity would not increase anymore.Passing through buffer solution could not elute all the enzymes.There was still a fraction of enzymes adsorbed on the cellulose films irreversibly.The longer the adsorption time was,the larger amount of enzymes on the cellulose film surface adsorbed.The later the elution time started,the larger amount of the cellulase with irreversible adsorption on the cellulose surface would be.Adsorption,desorption,and irreversible rate contant were characterized using Langmuir sorption kinetic model.Compared to Cel7 B,Cel7A had a larger Langmuir Equilibrium constant,by adsorbing more quickly and desorbing more slowly,and exhibited a higher affinity to cellulose films.The irreversible adsorption rate contant of Cel7 A was smaller,maybe due to the less denaturation on the cellulose films.