Lignin Peroxidase Activity Is Not Important in Biological Bleaching and Delignification of Unbleached Kraft Pulp by Trametes versicolor

Abstract

The discovery in 1983 of fungal lignin peroxidases able to catalyze the oxidation of nonphenolic aromatic lignin model compounds and release some CO2 from lignin has been seen as a major advance in understanding how fungi degrade lignin. Recently, the fungus Trametes versicolor was shown to be capable of substantial decolorization and delignification of unbleached industrial kraft pulps over 2 to 5 days. The role, if any, of lignin peroxidase in this biobleaching was therefore examined. Several different assays indicated that T. versicolor can produce and secrete peroxidase proteins, but only under certain culture conditions. However, work employing a new lignin peroxidase inhibitor (metavanadate ions) and a new lignin peroxidase assay using the dye azure B indicated that secreted lignin peroxidases do not play a role in the T. versicolor pulp-bleaching system. Oxidative activity capable of degrading 2-keto-4-methiolbutyric acid (KMB) appeared unique to ligninolytic fungi and always accompanied pulp biobleaching.

Aryl alcohols in the physiology of ligninolytic fungi

“…The table clearly demonstrates that the ligninolytic enzyme complex is not so homogeneous among white-rot fungi as once thought [3]. However, it should be kept in mind that the detection of 159 ligninolytic enzymes in the culture broth is often difficult because of the association of the enzymes to the fungal mycelium [85] and/or the occurrence of inhibitors in the culture broth [86][87][88][89].…”

“…Purified enzyme can give depolymerization of a synthetic lignin (DHP) [163], and also degrades high molecular mass chlorolignins [164]. MnP is the predominant enzyme involved in kraft pulp bleaching [89,165] and the decolorization of bleach plant effluents [155].…”

Lignin-modifying enzymes from selected white-rot fungi: production and role from in lignin degradation

“…Reactions of LiP using a variety of lignin model compounds and synthetic lignin have thoroughly been studied, catalytic mechanisms elucidated and its capability for C~-C~ bond cleavage, ring opening and other reactions has been demonstrated [1,16]. However, its exact role in lignin biodegradation and in other related processes such as pulp bleaching, pulp mill effluent decolorization and detoxification of environmental pollutants has frequently been questioned [17][18][19].…”

“…An interesting laccase ('Laccase III'), which apparently degrades lignin model compounds and causes depolymerization of lignin, has been described in C. t,ersicolor [40]. C. cersicolor has extensively been studied for biobleaching of pulp [19,21]. Prior to P. chrysosporium, this fungus was considered as a 'standard' white-rot fungus and was frequently used in studies.…”

“…it degrades wood carbohydrates and lignin at the same proportional rate [1]. The essential role of LiP in biobleaching and delignification by this fungus is doubtful [19]. Instead, MnP is considered an important and essential enzyme in demethylation and delignification of pulp by C. t,ersicolor [21].…”