Extracellular activities and wood component losses during Pinus taeda biodegradation by the brown-rot fungus Gloeophyllum trabeum

Abstract

Gloeophyllum trabeum is a brown-rot fungus that may hold promise for use in biorefineries. In the present work, G. trabeum was grown on Pinus taeda wood chips under solid-state fermentation conditions to study the degradative mechanisms used by this fungus. Metabolite secretion, Fe3+-reducing activity and wood component losses were evaluated in the cultures. The average mass loss ranged from 4% to 7% (m/m) during the period of 1–4 weeks. Polyoses were degraded preferentially. Cellulases and xylanases were secreted, but no correlation between hydrolytic enzymes and wood polysaccharide losses was observed. No phenol-oxidizing enzyme activity was detected. Soluble oxalic acid was detected in trace quantities. The residual lignin content remained unchanged (28.5% m/m), but mass balance studies indicated that Pinus taeda wood chips were partially delignified. This delignification was not accompanied by the accumulation of water-soluble phenols with Fe3+-reducing activity. The data suggest that Fenton-based biodegradation of wood polysaccharides by G. trabeum may be independent of lignin degradation products with Fe3+-reducing activity.