Adsorption And Hydrolyzability Of Hemicelluloses On Cellulose

Hemicelluloses(xylans and mannans)are the secondary polysaccharides that build up the complex cell wall of plants.Hemicelluloses have an inherent affinity to cellulose and will thus adsorb irreversibly on cellulose surfaces during the processing of ligcelluloses pretreatment and papermaking industrial processes.The adsorption of hemicelluloses on cellulose is important to the processing of efficient cellulose enzymatic hydrolysis and papermaking industrial processes,but the adsorption behavior and mechanism is not so clear.Therefore,the adsorption of hemicelluloses on celluloses,the hydrolyzability of adsorbed hemicelluloses,and the structure of hemicelluloses were investigated in this study.The aim of this study was to investigate the inhibition of adsorbed hemicelluloses on cellulose hydrolysis,and the adsorption behavior of hemicelluloses on celluloses and the hydrolysis of adsorbed hemicelluloses by hemicellulases.Thus,this study could be further extended to the theoretical foundation of the efficient lignocelluloses hydrolysis and enzymatic adjustment of paper quality.Research results as follow:1.The beechwood xylan(BWX)is 2,3-di-O-acetylated 4-O-methyl-?-D-glucuronoxylan,the oat spelt xylan(OSX)is ?-D-(1,4)-linked D-xylopyranosyl residues substituted with 3-O-?-L-arabinofuranosyl.The structure of glucomannan(GM)and galactomannan(GalM)is straight chain of D-mannopyranosyl and D-glucopyranosyl units and linear chain of ?-D-1,4-linked D-mannose residues with 1,6-linked D-galactose side groups,respectively.The corn stover xylan(CS-xylan)is 3-O-?-L-arabinofuranosyl xylan.2.The glucose yields of Avicel after 6 h hydrolysis decreased about 1%-9% after adsorption of xylans and mannans.This could be due to the adsorption of hemicelluloses on cellulose surface and the binding of hemicelluloses to the active sites of CEL.3.This study further investigated the adsorption behavior and mechanism of hemicelluloses on cellulose.It was observed that the adsorbed amount of xylans and mannans increased along with the increasing loading concentration,and the adsorbed amount of OSX and mannan was higher than other xylans and mannans.The adsorption of BWX on Avicel/CS-DA and OSX on Avicel was conformed to Langmuir-type adsorption isotherm,and the strength of affinity of BWX and Avicel(43.42 mL/g Avicel)was highest.The amount of BWX adsorbed on Avicel increased with the increase of ion strength,but the effect of ion strength to the OSX adsorption was not so obvious.After 6 h of incubation with an initial mannan concentration of 5 mg/mL,the adsorbed amount of mannan on Avicel(94.4 mg/g Avicel)was higher than that of GM(65.7 mg/g Avicel)and GalM(44.3 mg/g Avicel)on Avicel.4.The hydrolyzability of adsorbed hemicelluloses showed that both xylans and mannans adsorbed on celluloses could be hydrolyzed by xylanase and mannanase,and the hydrolysis ratios of BWX and mannan were higher than those of OSX,GM,and GalM.Additionally,the addition of hemicellulases could hydrolyze the hemicelluloses adsorbed on cellulose and potentially improved hydrolysis efficiency of lignocelluloses in different degrees.Above all,the addition of hemicellulase could affect the hemicellulose adsorption and further decrease the inhibition of adsorbed hemicelluloses in cellulose hydrolysis by CEL.What is more,it chould further be applied to the enzymatic adjustment of paper quality in the paper industry.