Microbial degradation of lignin: Role of lignin peroxidase, manganese peroxidase, and laccase

Abstract

Lignin peroxidase (LiP), laccase (LA) and manganese peroxidase (MnP) of white-rot basidiomycetes such as Phanerochaete chrysosporium, Coliorus versicolor, Phlebia radiata and Pleurotus eryngii catalyze oxidative degradation of lignin substructure model compounds and synthetic lignins (DHPs). Side chain- and aromatic ring cleavage products of both phenolic and non-phenolic substrates oxidized by LiP were isolated and characterized by NMR and MS. The cleavage mechanism was elucidated by using 18O, 2H, and 13C labeled lignin substructure dimers with 18O 2 and H218O. Recent studies suggested that LiP is capable of oxidizing lignin directly at the protein surface via a long-range electron transfer process. LA and MnP, which oxidize phenolic but not non-phenolic moieties, generally degrade lignin stepwise from phenolic moieties. However, recent studies indicated that MnP and LA can degrade both phenolic and non-phenolic aromatic moieties of lignin with some special mediators. (Communicated by Yasuyuki YAMADA, M.J.A.)