Mechanism Of The Enhancment Of Chemical Additives To The Hydrolysis Of Biomass

As the key process of the bio-ethanol production,the enzymatic hydrolysis of lignocellulosic material is limited by the structure of lignocelluloses,the denaturation of enzymes to low yields and high cost price.In this work,the effects of BSA,PEG,and Tween on the hydrolysis of lignocelluloses by cellulase and xylanase were investigated.The mechanism of the effects of chemical additives on the enzyme adsorptions onto substrates,and the desorptions of enzymes from the substrates was also investigated.The purpose of this research is to investigate the nonproduction adsorption behavior of cellulase and xylanase onto lignin,aiming at reducing the dosage of enzymes and increasing the hydrolysis yield,and reducing the production cost of the fermentable sugars.The effects of the chemical additives in the cellulase and xylanase hydrolysis were investigated.As shown in the results,the hydrolysis yields of Avicel and corn stover by both comnination and individual xylanase and cellulase were enhanced by the chemical additives,while the synergy factor of xylanase and cellulase was decreased with the presence of chemical additives.The mechanism of chemical additives to enhance the hydrolysis was shown as that,the adsorption on the lignin was reduced to increased the opportunity for the adsorption of enzymes onto cellulose or hemicelluloses,and the thermal stability of the enzyme was protected with the enzyme inactivation was prevented by the chemical additives.The nonproduction adsorption of enzymes onto lignin is one of the main limiting factors in the hydrolysis of lignocelluloses.Effect of chemical additives to the adsorption or desorption of cellulase and xylanase on or from the corn stover lignin,wheat straw lignin,corn stover,xylan or Avicel were investigated.The results showed that the cellulase or xylanase bound to lignin,corn stover,and Avicel or insoluble oat spelt xylan was still productive.Chemical additives could not only affinite with the lignin in the hydrophobic group affiliation,occupy the adsorption sites,effectively reduce the adsorption of enzyme onto lignin,but also could adsorbed on the cellulose and xylan,reduce enzyme on the effective components of meaningless adsorption,free the enzyme to the solution to hydrolysis.For different substrates,the effects of chemical additives were from high to low in the order of lignin,corn stover,xylan or Avicel.After the adsorption of enzymes onto substrates,the amount of enzymes desorbed from substrate with additive were more than with buffer,and the hydrolysis ability of the enzymes bound to substrates was also reduced.It was suggested that a part of enzymes bound to substrate were replaced by the chemical additives,and the enzymes were free to solution to adsorb and hydrolyze the substrates.The effect of chemical additives was in correlation with their concentration,the optium PEG 6000 concentration was 2.5 mg/g substrate.The chemical additives not only enhanced the hydrolysis by cellulase,but also the hydrolysis by xylanase.In addition,the chemical additives reduced the enzye adsorption and the desorption from the lignin,cellulose and xylan.To know the mechism of the effects of chemical additives on the adsorption and desorption of lignocellulosic enzymes,is necessary to achive the recycling and efficient use of the enzymes.