Immunolabelling studies on the detection of enzymes during the degradation of wood by Phanerochaete chrysosporium

IRG/WP 1364

G F Daniel, T Nilsson, B Pettersson

The degradation of lignin in native lignocellulosic substrates by white rot fungi is poorly understood. Biochemical studies have shown the involvement of a number extracellular ligninolytic enzymes released by white rot fungi which are capable of the oxidative conversion of DHP's (lignin model compounds) in vitro, but to date conclusive evidence for occurrence of these enzymes in wood undergoing degradation is limited. In the present work, the distribution of lignin peroxidase during the degradation of Betula verrucosa and Pinus sylvestris by the ligninolytic fungus Phanerochaete chrysosporium (wild type) was studied by using antisera produced against the purified enzyme in conjunction with appropriate light and electron microscopic immunological detection methods. Light microscopic immunofluorescence and immunocytochemical observations showed the enzyme to be closely associated with both the fungus and exposed sites of erosion decay of the wood fibres. This was confirmed by post-embedding TEM immunolabelling studies using gold labelling methods which showed the enzyme to be localized within the peripheral fungal cell cytoplasm, cell membrane, fungal cell wall regions and occassionally extracellular slime materials. Similar gold-labelling methods showed enzymic localization along areas of lumen wall erosion of birch fibres at various stages of decay. Labelling occurred on all cell wall layers including the middle lamella when exposed. The distribution of the enzyme in degrading pine fibres was also restricted to sites exposed during erosion decay. In contrast comparative cytochemical studies performed with 3' 3' diaminobenzidine for general peroxidase enzymes suggested an intracellular distribution within the S2 cell wall of degrading fibres. The enzyme distribution was seen to have a close association with characteristic zones of decay which radiated out from the inner fibre wall regions during attack. Possible reasons for the disparity in the results are discussed as are the implications for the apparent restriction of lignin peroxidase to exposed surface regions of wood fibres during degradation.


Keywords: PHANEROCHAETE CHRYSOSPORIUM; WHITE ROT; DECAY; BETULA VERRUCOSA; PINUS SYLVESTRIS; LIGNIN PEROXIDASE; ANTISERA; GOLD IMMUNOLABELLING; IMMUNOCYTOCHEMISTRY; IMMUNOFLUORESCENCE; TEM; ENZYMES

Conference: 88-04-24/29 Madrid, Spain


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