Carboxylated and quaternized lignin enhanced enzymatic hydrolysis of lignocellulose treated by p-toluenesulfonic acid due to improving enzyme activity

• Carboxylated and quaternized lignin (CQL) enhanced hydrolysis. • Hydroxymethylated lignin (HML) inhibited hydrolysis. • CQL increased but HML reduced β-glucosidase (β-GL) activity. • Molecular docking results showed that CQL-β-GL complexes had a lower binding free energy. • Binding site of HML and β-GL overlapped with carbohydrate binding domain of β-GL. Modificated lignins can affect enzymatic hydrolysis efficiency (EHE) because of changing physicochemical properties of lignin. In this study, carboxylated and quaternized lignin (CQL) and hydroxymethylated lignin (HML) were prepared to explore the effect of lignin modification on cellulase adsorption and EHE of p-toluenesulfonic acid treated corn stover (PCS). The results showed that CQL enhanced EHE of PCS due to the higher β-glucosidase (β-GL) activity, resulting from the formation of CQL-β-GL complexes with a lower binding free energy and the improvement of β-GL conformation made by the binding of CQL and β-GL. However, the drop in EHE due to the addition of HML was consequent on β-GL deactivation that was because the binding site of HML and β-GL overlapped with the carbohydrate binding domain of β-GL, causing the decrease in β-GL activity compared with CQL. This study would help deeply elucidate the effect of modified lignins on EHE and cellulase adsorption.