The effect of manganese on lignin peroxidase activity was studied. The enzyme was produced with a new process using an air-lift-type reactor. The experiments were performed with veratryl alcohol and a dimeric lignin model compound. It was shown that when Mn(I1) . lactate complex was present the amount of veratraldehyde formed and the uptake of oxygen were significantly enhanced during the aerobic oxidation of veratryl alcohol. A similar effect can be obtained with superoxide dismutase. These results strongly suggest that the superoxide anion can occur during the reaction; its scavenging by Mn(I1) or superoxide dismutase generates H202. In contrast, no evidence for the formation of superoxide anion was found during oxidation of the lignin model, compound veratrylglycerol-/3-guaiacyl ether.The discovery of the extracellular ligninolytic system of the white-rot fungus Phanerochaete chrysosporium [1, 21 has renewed interest in biodelignification. The constituents of this system have been identified as two types of peroxidase, now referred to as lignin peroxidase or ligninase, and manganesedependent peroxidase. Recently, Kersten et al. [3] demonstrated an H202-generating system, a glyoxal oxidase in ligninolytic cultures.Lignin peroxidase is able to catalyse a variety of reactions in lignin model compounds. This enzyme functions by singleelectron oxidation, leading to cation radical intermediates [4, 51; their further decomposition and the evolution of the radical-moiety depend on their chemical structure [6 -91. Such a mechanism could explain the non-specificity of lignin-peroxidase-catalyzed reactions, and makes this enzyme important for lignin depolymerisation.The activity of manganese-dependent peroxidase toward phenolic substrates depends on the presence of manganese [lo, 111. This peroxidase oxidizes Mn(I1) to Mn(III), which is in fact the effective oxidative agent involved in the enzymic reactions [12].As lignin is a complex polymer, its biodegradation may require some synergy between enzymes. In this paper, we examine if manganese also has an effect on lignin peroxidase activity. For this purpose, lignin peroxidase was isolated from the culture fluid of P. chrysosporium grown in an air-lift-type reactor, with a glycerol/high-nitrogen-supplemented medium. The experiments were performed with two substrates, veratryl alcohol, a secondary metabolite produced by the fungus during lignin biodegradation [13], and veratrylglycerol-P-guaiacyl ether, a dimeric lignin model compound.

No abstract

No abstract