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Oxidative lignin modification is a chemical and biochemical process that alters the molecular structure of lignin through controlled oxidation reactions, wherein electron transfer from lignin's aromatic subunits generates reactive radical intermediates that subsequently undergo bond cleavage, coupling, or oxyfunctionalization ^[1]. Lignin, a complex polyphenolic biopolymer composed of methoxylated phenylpropanoid units (guaiacyl, syringyl, and p-hydroxyphenyl) linked by ether and carbon–carbon bonds, possesses two distinct classes of oxidizable sites: phenolic hydroxyl groups, which are readily oxidized at relatively low redox potentials, and non-phenolic moieties, which require higher oxidation potentials or the presence of redox mediators to undergo transformation ^[2]. The oxidation of phenolic units proceeds via one-electron abstraction to yield phenoxy radicals, which can delocalize across the aromatic ring and participate in radical–radical coupling reactions that form new interunit linkages (C–C, C–O, or C–N bonds), or undergo further two-electron oxidation to quinone or quinone methide intermediates that are susceptible to nucleophilic attack ^[3]. Non-phenolic units, particularly the abundant β-O-4 aryl ether linkages, can be oxidatively cleaved through mechanisms involving benzylic Cα-oxidation to ketone or carboxyl functionalities, followed by β-ether bond scission, or through direct attack on the aromatic ring mediated by high-potential oxidants ^[4]. Oxidative lignin modification is effected through diverse catalytic systems, including fungal multicopper oxidases (laccases), class II peroxidases (lignin peroxidase, manganese peroxidase, and versatile peroxidase), ortho-methoxyphenolases, and synthetic chemical oxidants (metal complexes, TEMPO-based systems, electrochemical and photochemical oxidants), each operating through distinct mechanistic pathways and exhibiting different substrate selectivities ^[5]. The term encompasses both degradative transformations that depolymerize lignin into lower-molecular-weight fragments and constructive transformations that increase molecular weight or introduce new functional groups, and is distinguished from reductive lignin depolymerization by its reliance on oxidizing agents rather than reducing agents, and from lignin biosynthesis by its occurrence under exogenous, non-physiological conditions ^[1].