Sructural features of lignin determining its biodegradation by oxidative enzymes and related systems

Peroxidases and laccases are key enzymes in the lignin biodegradation process. They oxidize phenolic and non-phenolic lignin model compounds into their phenoxy and cation radicals, respectively. Further non-enzymatic evolution lead then to various C-C and ether bond cleavages. Nevertheless, almost no information on the structural alterations undergone in vitro or in situ by lignin after enzymatic catalysis is available. We report here on the molecular structure of lignin oxidized by various (per)oxidasic systems. The oxidizability of phenolic and non-phenolic structures of the guaiacyl and syringyl type in the lignin network will be discussed as well as the modification of the macromolecular properties of the polymer oxidized in situ or in isolated state.