Effect Of Combined Pretreatment Technology Based On Lignin In-situ Modification On Lignocellulosic Enzymatic Hydrolysis

n terms of the non-productive adsorption of lignin on cellulase during the enzymatic hydrolysis of lignocellulose,the carboxyl,sulfonate and oxidation groups were introduced into commercial alkaline lignin to prepare the sulfonated lignin?SL?,oxidized lignin?OL?,and carboxylated lignin?CL?,to investigate the interaction between modified lignin and cellulase for improving the glucose yield of cellulose enzymatic hydrolysis.The results showed that after modifying,the content of phenolic hydroxyl group and hydrophobicity of AL decreased by 17-80%and 61-80%respectively;the electronegativity increased by 21-45%.The 72 h glucose yield of microcrystalline cellulose?Avicel?-modified lignin hydrolytic system was 48.5%?Avicel-SL?,51.3%?Avicel-OL?and 49.4%?Avicel-CL?respectively,which was 8-15.3%higher than that of Avicel-AL?44.5%?.Also,the content of free enzyme in Avicel-modified lignin hydrolytic systems increased by 14-15%compared with that of Avicel-AL after 72 h of hydrolysis.We concluded that the adsorption between modified lignin and cellulase enzyme was mitigated and the-SO₃,-COOH were synergistic factors of enzymatic hydrolysis.The sugarcane bagasse?SCB?was carried out three combined treatments which employed sulfomethylation,oxidation and carboxylation as post-treatments based on alkaline pretreatment.The component of treated biomass showed that alkaline pretreatment removed 52.53%of lignin in SCB and alkaline-sulfomethylation,oxidation,carboxylation treatments removed 75.19%,68.28%and 70.52%of lignin respectively,which was 30-43%higher than alkaline pretreatment alone.The sulfomethylation post-treatment made the glucose yield and free enzyme concentration of AP-SCB increased by 60.43%and 1.20 times;the carboxylation post-treatment made these of AP-SCB increased by 72.68%and 0.96 times;however,oxidation post-treatment had little effect on the reducing sugar yield of AP-SCB.The residual lignin in each combined treated SCB was isolated and extracted to determine its surface properties and structural characteristics.The results showed that,after combined treatments,the O/C of residual lignin in SCB was decreased.Sulfomethylation and carboxylation post-treatment broke the?-O-4 linkages in residual lignin.Sulfomethylation post-treatment introduced the-SO₃ onto surface of residual lignin;the content of C-O was increased;the hydrophilicity and electronegativity of residual lignin were improved by 32.87%and 59.28%respectively.Carboxylation post-treatment introduced the aliphatic carbonyl group onto the surface of residual lignin;the content of C-O and O-C=O was increased;its hydrophilicity and electronegativity were improved by 29.31%and 9.17%,respectively.The hydrophilicity and electronegativity of residual lignin were improved after sulfomethylation and carboxylation so that the adsorption capacity of residual lignin on cellulase was weakened.