Insights into acidic deep eutectic solvent-mediated softwood pretreatment for high fermentable sugar yield and efficient lignin recovery

This study addresses the critical challenges of softwood pretreatment, focusing on Chinese fir as a model substrate to tackle its high lignin content and recalcitrant structure. To enhance the fractionation efficiency of softwood components and improve enzymatic glucose yield, four deep eutectic solvent (DES) systems—ChCl/LA, ChCl/FA, TEBAC/LA, and TEBAC/FA—were systematically evaluated. Using density functional theory (DFT) calculations and molecular dynamics (MD) simulations, TEBAC/LA (1:4) was identified as the optimal DES system, exhibiting exceptional binding energy (-162.37 kcal/mol) and strong hydrogen bonding interactions that effectively disrupted lignin’s hydrogen bond network. Furthermore, Pearson correlation analysis between the physicochemical properties of DES (e.g., density, viscosity, surface tension, and Kamlet-Taft parameters) and enzymatic hydrolysis yield revealed that low surface tension, high Kamlet-Taft α, and high π parameters significantly enhance pretreatment efficiency. Guided by these computational insights, experimental validation revealed that TEBAC/LA achieved outstanding lignin removal (97.41 %) and glucose yield (97.09 %) under optimized conditions (150 °C, 90 min). This work not only advances the understanding of DES-biomass interactions but also demonstrates the power of integrating molecular simulations with experimental validation to design efficient biomass pretreatment systems. This study provides a scalable and sustainable approach for optimizing solvent systems, advancing renewable energy and material production.