From Waste to Wealth: Integrating Biological Systems and Molecular Intelligence for Lignin Valorization

Lignin is an abundant and renewable aromatic polymer, but its structural heterogeneity hinders its efficient bioconversion. Unlike previous reviews that focused on isolated topics such as single enzymes, pathway engineering, or specific bioproducts, this paper comprehensively reviews the latest advances in the structural characteristics, microbial degradation mechanisms, and bioconversion of lignin. Particular emphasis is placed on the catalytic mechanisms of key lignin-degrading enzymes, including laccase, lignin peroxidase (LiP), and manganese peroxidase (MnP), as well as the applications of fungi, bacteria, and synthetic microbial consortia in lignin bioconversion. Metabolic pathways that channel heterogeneous lignin-derived aromatics into central carbon metabolism through sequential catalytic reactions are also covered. Furthermore, we evaluate the emerging applications of artificial intelligence and machine learning in enzyme design and bioprocess control. Finally, techno-economic and life-cycle considerations are integrated to guide large-scale deployment. This review provides in-depth insights into the cross-scale translation from laboratory biocatalysis to industrial biorefineries.