Quantification of fungal degradation of pinus patula and eucalyptus grandis.

Abstract

Previous studies of fungal decay have mainly examined long term effects of wood decay. In contrast, the present work, was designed to quantify fungal degradation of wood during incipient decay. Three facultatively anaerobic, dimorphic fungi were isolated from the rumen of sheep. These fungi were identified as Mucor racemosus, Candida tropicalis and Geotrichum capitatum. Scanning electron microscopy showed that these fungi colonised Pinus patula and Eucalyptus grandis extensively but did not appear to degrade the wood. The obligate anaerobe Neocallimastix frontalis colonised wood very sparsely, whereas the white rot bas id iomycetes Cori 01 us versicolor, and Phanaerochaete chrysosporium, and the brown rotters Coniophora puteana and Lentinus lepideus, colonised wood under both aerobic and anaerobic conditions. The extents of colonisation were greater under aerobic conditions. The work then quantified the effects of the basidiomycetes C. versicolor, P. chrysosporium, C. puteana and L .lepideus, and the non-decay mould, M. racemosus in individual and coculture experiments. Wood colonisation was quantified by Kjeldahl nitrogen determinations converted to biomass assays, and degradation was quantified by weight losses, and Klason lignin determinations. Furthermore, the degraded wood samples were also analysed by HPLC analysis of hydrolysates and their sugar contents were determined to establish whether the glucose of cellulose and xylose + mannose of hemicellulose had been utilised by the respective fungi. The extent and nature of sugar utilisation by monocultures and cocultures in wood were then compared with the biomass and degradation data. statistical analyses of' these comparisons correlated the extents of colonisation, degradation, and the patterns of wood sugars predominantly utilised by each fungus. The results of the corresponding glucose, xylose and 'lignin analyses confirmed the brown rot physiological capacity of C.puteana in both'woods. The white rot fungi behaved as simultaneous rotters and,<M·~<.racemosus was shown to be ligninolytic in P .patula. The white rot physiological capacity of C.versicolor was confirmed in 'E.grandis and that of P.chrysosporium in P.patula. Antagonism and synergism in wood was detected between individuals 'within cocultures during incipient decay. The significance of these findings becomes apparent when decayed wood of unknown history is analysed as described here. Such findings may be interpreted to provide valuable information describing the physiological nature of the responsible fungi, even if these are no longer viable or culturable.