Coupling of manganese peroxidase-mediated lipid peroxidation with destruction of nonphenolic lignin model compounds and C-14-labeled lignins

Linoleic acid, the predominant unsaturated fatty acid (UFA) in the lipids o f wood-rotting fungi, was oxidized by manganese peroxidase (MnP) from the w hite-rot fungus Phlebia radiata through a peroxidation mechanism. The perox idation was markedly stimulated by hydrogen peroxide. UFAs that are substra tes for lipid peroxidation and surfactants that emulsify water-insoluble co mponents were essential for the MnP-catalyzed destruction of a nonphenolic beta-O-4-linked lignin model compound (LMC). Moreover, both components stim ulated the MnP-catalyzed mineralization of C-14-labeled synthetic lignin an d C-14-labeled wheat straw. A high level of destruction was obtained in rea ction systems with Tween 80 acting both as surfactant and source of UFAs. T he presence of the linoleic acid in reaction systems with MnP and Tween 80 additionally enhanced rate and level of LMC destruction and lignin minerali zation. The results indicate that lipid peroxidation may play an important role in lignin biodegradation by wood-rotting basidiomycetes and support th e hypothesis of coupling between the processes. (C) 1999 Academic Press.