The Adsorption And Inhibition Of Lignocellulosic Enzymes By Lignin

Lignin is one of the main components of lignocelluloses and its existence decrease the accessibility of lignocellulosic enzymes to substrates and the hydrolysis yields.Thus,evaluating the role of lignin in the enzymatic hydrolysis provides theoretical basis for the efficient usage of lignocellulosic biomass in the producing of biological liquid fuel and relevant high-value chemicals.This paper started with different lignocellulosic materials etc.as materials to study the effects of lignin on enzymatic hydrolysis,the adsorption capacity of enzymes onto relevant substrates when different dosages enzyme were applied,and the hydrolyzalibilities of the lignin-bound enzymes.The results showed that the lignin content exhibited negative relationship with the hydrolysis yields of the pretreated corn stover fractions.Took corn rind as an example,the hydrolysis yields of corn rind were improved significantly after the removal of lignin by aqueous ammonia pretreatment.The hydrolysis yield of corn rind was increased by 45%after 24 hours ammonia pretreatment.X-ray diffraction and scanning electron microscope analysis supported that aqueous ammonia pretreatment improved the porosity of substrates,decreased the crystallinity of substrates,and thus improved the accessibility of enzymes to substrates and increased the hydrolysis yields of substrates.The application of lignin inhibited the hydrolytic capability of cellulases or xylanases.The inbition ratio of 10 mg lignin/g DM to the hydrolysis of Avicel was 34%,indicating that lignin decreased the hydrolytic ability of cellulases.Data showed that lignin could adsorb cellulase and xylanase,and the adsorbed cellulase could hydrolyse Avicel and cellulose in corn stover,and the adsorbed xylanase could hydrolyse beechwood xylan and xylan in corn stover.Besides,the amount of lignin-bound enzyme increased with the increase of lignin dosage,showing that the adsorption of enzymes onto lignin was relevant to the dosage of enzyme.In the adsorption experiments,the adsorption abilities of enzymes onto lignin differed with different enzymes and different lignin preparations.When 1%lignin and 4 mg/ml enzymes was supplied,the adsorption capacity of Celluclast 1.5L onto sulfuric acid pretreated corn stover was 41.1 mg/g substrates and the adsorption capacity of Novozyme 188 onto lignin prepared from corn stover was 47.8 mg/g lignin;the adsorption capacity of Ta Xyl onto lignins(enzymatic prepared lignin,80.4 mg/g lignin;acid-insoluble lignin 57.3 mg/g lignin)was higher than that onto wheat straw(47.4 mg/g substrates).It was also showed that the content of cellulases and xylanases on the surface of lignin exhibited clearly linear relationship with the concentration of reducing sugars.Lignin inhibited the hydrolytic ability of cellulases and xylanase,and the lignin left in lignocelluloses after pretreatment could adsorb enzymes onto lignin,which induced part loss of hydrolytic ability of enzymes and decreased the efficiency of hydrolysis.Therefore,the removal of lignin in lignocelluloses by efficient pretreatment methods was significant to the improvement of hydrolysis yield.This study further verified the role of lignin on enzyme molecule and hydrolysis efficiency.The results provided the efficient pretreatment methods and the development of enzymic preparations with ideas,and supplied the found of efficient enzymatic hydrolysis techniques with theoretical basis.