Effect of Carboxylated and Quaternized Lignin and Epoxidized Lignin on Enzymatic Hydrolysis of Corn Stalk

Lignin structure is known to have significant effects on the enzymatic hydrolysis efficiency (EHE) of lignocellulose. In this study, the lignin produced from corn stalk pretreated with p-toluenesulfonic acid (PCS) was used to prepare carboxylated and quaternized lignin (CQCL) and epoxidized lignin (ECL), and the effect of the two modified lignin forms on the EHE of PCS was investigated. The results showed that EHE after adding CQCL (83.7%) was higher than adding ECL (60.8%). To explore the reasons, the unproductive adsorption, cellulase-lignin interaction, and molecular dynamics experiments were conducted. The results showed that the smaller hydrophobic interaction and electrostatic attraction between CQCL and cellulase caused less unproductive adsorption between CQCL and cellulase than ECL. Additionally, CQCL and ECL changed differently the conformations of key amino acid residues of cellobiohydrolase I and endoglucanase II, which was also responsible for the higher EHE after adding CQCL.