Mild synergistic ethylenediamine-sodium carbonate pretreatment for high glucose yield and lignin degradation mechanism

Efficient pretreatment is essential for unlocking the biorefining potential of lignocellulosic biomass. In this study, a mild and synergistic pretreatment strategy was established using ethylenediamine (EDA) and sodium carbonate (Na₂CO₃) at 85°C under atmospheric pressure. Following optimization, the process enabled effective fractionation of corn stover, removing 85.17 % of lignin while retaining 66.52 % of cellulose, and subsequently achieving a 92.57 % enzymatic glucose yield (0.68 g/g substrate). Mechanistic analyses integrating FTIR, semi-quantitative GC-MS, and DFT calculations revealed that the synergistic interplay between EDA and Na₂CO₃ promotes cleavage of dominant lignin interunit linkages. EDA forms stabilizing hydrogen bonds and facilitates nucleophilic substitution at the C α position, whereas the alkaline environment generated by Na₂CO₃ favors oxygen-anion formation at the C β site, collectively driving lignin depolymerization. As a result, lignin is selectively converted into soluble products, including identifiable aromatic monomers. The pretreatment system also exhibited strong recyclability, maintaining 63.60 % lignin removal and 75.44 % glucose conversion after six reuse cycles. Overall, the EDA-Na₂CO₃ strategy enables high sugar yields under mild, low-energy conditions, offering a promising and sustainable pathway for integrated lignocellulosic biorefining. • Mild EDA-Na₂CO₃ pretreatment achieves 85 % lignin removal and 92 % glucose yield at 85°C. • Dual activation selectively cleaves C α -O and C β -O bonds, promoting efficient lignin depolymerization. • High recyclability maintained over seven cycles, with > 63 % lignin removal and > 75 % glucose yield. • Superior to conventional alkaline methods in sugar yield and cellulose preservation under milder conditions.