The simultaneous optimization of detoxification for ferulic acid and saccharification processes using highly efficient modified lignin

Abstract

A novel modified lignin adsorbent was prepared from residual lignin in alkali-pretreated rice straw. Density functional theory (DFT) calculations were used to select the optimal modification method, aiming to create an efficient adsorbent with strong affinity for ferulic acid and minimal binding to cellulase. The DFT results showed that sulfomethylated lignin had a high binding affinity of −15.655 kcal mol⁻¹ and the shortest hydrogen bond length (1.76 Å) with ferulic acid. In contrast, it had a lower binding affinity of −11.390 kcal mol⁻¹ and a longer Pi-Pi stacking distance (3.36 Å) with cellulase. Compared to other adsorbents, sulfomethylated lignin demonstrated a higher adsorption efficiency for ferulic acid (72.85 %). Quartz Crystal Microbalance with Dissipation Monitoring (QCM-D) curves indicated a reduction in nonproductive adsorption between modified lignin and cellulase. The adsorption of ferulic acid by modified lignin fitted the pseudo second-order model better, suggesting that the process was primarily driven by chemical interactions such as ion exchange or electrostatic attraction. Additionally, the reduction in nonproductive adsorption of cellulase was associated with changes in the electronegativity and hydrophobicity of the modified lignin. This study simultaneously reduced the ferulic acid toxicity and cellulase nonproductive adsorption, achieving dual benefits in detoxification and saccharification processes.