Green synthesis of aminated lignin via biocatalytic pathway for removal of Cu( <scp>II</scp> ) from wastewater

Abstract The amination of lignin is crucial for its high‐value utilization, but conventional chemical methods suffer from low selectivity and environmental drawbacks. Here, the amination of industrial alkali lignin was achieved for the first time via a biocatalytic pathway. A cascade catalytic system was constructed based on the mechanistic analysis of lignin model compounds. Aryl alcohol oxidase (AAO) selectively oxidizes hydroxyl groups, while ω‐transaminase (ω‐TA) mediates the transamination of aldehyde groups. The –NH 2 group ratio in nitrogen reached 93.63% in bio‐aminated lignin (EAL1), reflecting a ~9% increase over chemically aminated lignin (AAL1). The enzymatic pathway enabled efficient and selective amination, avoiding byproducts and structural damage from traditional Mannich reactions. Notably, EAL1 exhibited 100% removal efficiency under the experimental conditions for low‐concentration Cu(II) solution via amino‐coordination chemisorption, as verified by density functional theory (DFT) calculations. This study presents a novel approach for green functionalization of lignin, demonstrating potential applications in wastewater treatment.