Ligninolytic activity of Phlebiopsis gigantea strains in cultivation on Norway spruce wood

Abstract

Abstract
 
 As a white-rot basidiomycetous and wood-decaying fungus, Phlebiopsis gigantea (Fr.: Fr.) Jülich is able to degrade lignin, cellulose and hemicellulose with a complex set of extracellular enzymes. Enzyme activity of this fungus has not been sufficiently explored.
 The aim of this study was to assess the activity of laccase and peroxidases as well as the level of micromolecular compounds in P. gigantea strains, grown on pieces of Norway spruce wood (sapwood and heartwood) over 50 days of incubation under laboratory conditions. Enzymatic activity was determined using spectrophotometry. Phlebiopsis gigantea strains showed laccase (Lacc), manganese peroxidase (MnP), lignin peroxidase (LiP) and versatile peroxidase (VP) activity. Hydroxy– and methoxyphenols were released during this process also. High levels of MnP activity (from 5.5 to 107.847 mU/μg of protein in cultures on sapwood and from 7.585 to 229.055 mU/μg of protein in cultures on heartwood) were observed in P. gigantea strains, as well as high activity of VP with manganese-oxidizing properties (from 3.36 to 61.708 mU/μg of protein on sapwood and from 1.7 to 254.479 mU/μg of protein on heartwood) compared with the other examined extracellular enzymes. The activity of Lacc ranged from 0 to 0.731 mU/μg of protein on sapwood and from 0 to 0.216 of protein on heartwood. LiP activity was also low and ranged from 0.025 to 0.593 mU/μg of protein on sapwood, and from 0.060 to 1.566 mU/μg of protein on heartwood. The activity of VP in terms of guaiacol-oxidizing properties ranged from 0.016 to 1.432 mU/μg of protein in cultures on sapwood, and from 0.042 to 1.238 mU/μg of protein on heartwood. Released hydroxyphenols for P. gigantea strains ranged from 39.204-129.157 μg of protocatechuic acid/ml in cultures on sapwood, and from 23.098-83.630 μg of protocatechuic acid/ml on heartwood. Methoxyphenols produced by P. gigantea strains ranged from 7.5 to 22.987 μg of vanillin acid/ml on sapwood, and from 10.187 to 36.885 μg of vanillin acid/ml on heartwood.
 Keywords: white-rot fungus, Phlebiopsis gigantea, laccase, manganese peroxidase, lignin peroxidase, versatile peroxidase, hydroxy–, methoxyphenols.