Dual functionality of ethylenediamine pretreatment: Release of fermentable sugars and modified fluorescent lignin

The refining of renewable lignocellulosic resources requires energy-intensive and chemically harsh processes, leading to lignin condensation and carbohydrate loss. To efficiently convert corn cobs (CCs) into fermentable sugars and produce functionalized lignin, we developed an ethylenediamine (EDA) treatment system under high solid loads. At 140 °C, EDA treatment separated 75.87 ± 3.16 % of lignin while retaining 93.72 ± 2.78 % of cellulose. The introduction of amino and amide groups enhanced lignin hydrophilicity through electrostatic repulsion and hydrogen bonding with water, reducing non-productive enzyme binding. As a result, glucose and xylose conversion rates in cellulose solids (CSs) reached 85.17 ± 1.82 % and 75.34 ± 1.95 %, respectively, while xylan solids (XSs) released 90.87 ± 3.47 % of xylose within 12 h of enzymatic hydrolysis. Aminated lignin (AL) contained 14.33 % nitrogen, exhibited aggregation-induced emission, and showed a 4.88-fold enhancement in photoluminescence (PL) intensity compared to alkali lignin. Model compound studies for the first time revealed the nucleophilic attack mechanism of EDA on ester bonds and β-O-4 ether linkages. The solid-state reaction system and α-amination structure effectively blocked reactive sites to prevent lignin condensation. AL can serve as a low-cost fluorescent probe for rapid Fe 3+ concentration detection. This one-step separation system achieves simultaneous extraction and modification, simplifying downstream processing of carbohydrates and lignin for value-added applications.