The effect of copper on the growth of wood-rotting fungi and a blue-stain fungus

The effect of copper (II) ions on the growth of three brown-rot fungi, six white-rot fungi and one blue-stain fungus in solid medium was evaluated. The fungi were grown in malt extract agar with different concentrations of copper added, and the radial growth rate was determined. At the end of the incubation period, the mycelial biomass and the media pH were determined. The white-rot and blue-stain fungus grew up to 3 mM and 6 mM copper, respectively and the brown-rot fungi were the only ones that grew up to 10 mM, with higher growth rates than those shown by the other fungi. In general, the brown-rot fungi produced greater acidification in the culture media than the white-rot fungi and blue-stain fungus, and the acidification increased when the amount of copper was increased. The biomass production for the different species, in the absence or presence of copper, was not related to the radial growth rate, and the fungal species that produced the greatest biomass amounts did not correspond to those that presented the highest growth rates. The brown-rot fungi Wolfiporia cocos and Laetiporus sulfureus and blue-stain fungus Ophiostoma sp. demonstrated greater tolerance to high copper concentrations in solid medium than the white-rot fungi, determined as radial growth rate. On the other hand, the highest biomass producers in solid medium with copper added were the white-rot fungi Ganoderma australe and Trametes versicolor and the brown-rot fungus Gloeophyllum trabeum.     

Metabolic activities and ultrastructure imaging at late-stage of wood decomposition in interactive brown rot - white rot fungal combinations

Basidiomycota brown rot fungus (Fomitopsis pinicola) and two white rot fungi (Phlebia radiata, Trichaptum abietinum) were cultivated on thin slices of spruce wood individually and in interspecies combinations. Within 12 months, F. pinicola substantially decomposed spruce wood observed as mass loss, also in three-species combinations. However, white rot fungi through hyphal interactions negatively affected the brown-rot indicative iron reduction capacity of F. pinicola. Decay-signature gene expression in mycelial interaction zones indicated suppression of brown rot mechanism but stimulation of enzymatic white-rot lignin attack by P. radiata. Wood ultrastructure imaging showed white-rot dominance in the fungal combinations, whereas destructive brown-rot was evident with F. pinicola alone. Our results confirm the dynamic pattern of enzyme production in fungal combinations, and transition from brown to white rot decomposition metabolism during the late stage of wood decay after one year of interspecific interactions.     

Fungal bioleaching of metals in preservative-treated wood

Twenty-four brown-rot and 10 white-rot fungi were screened to evaluate their applicability for detoxification of preservative-treated wood impregnated with copper and chromium (CC) salts. Brown-rot fungi generally showed higher tolerance towards copper inhibition than white-rot fungi. Additionally, brown-rot fungi were found to accumulate considerable quantities of oxalic acid (up to 44.3 mM) in liquid medium, while white-rot fungi generally accumulated only traces of this organic acid. Oxalic acid is a strong organic acid capable of complexing a variety of heavy metals. Four Antrodia vaillantii and two Poria placenta brown-rot strains that displayed both a high copper tolerance and a high oxalic acid production were selected for further study. The brown-rot fungi effectively decayed wood containing up to 4.4% CC causing corrected mass losses of up to 24.3% in 4 weeks. Fungal treatment was also found to promote extensive leaching of chromium (up to 52.4%), but only moderate leaching of copper (15.6% or less). These results indicate the potential of solid-state fermentation with copper-tolerant fungi for the remediation of preservative-treated wood. Improving the solubility of copper will be an important challenge for future research.     

Solid-state fermentation in multi-well plates to assess pretreatment efficiency of rot fungi on lignocellulose biomass

The potential of fungal pretreatment to improve fermentable sugar yields from wheat straw or Miscanthus was investigated. We assessed 63 fungal strains including 53 white-rot and 10 brown-rot fungi belonging to the Basidiomycota phylum in an original 12 day small-scale solid-state fermentation (SSF) experiment using 24-well plates. This method offers the convenience of one-pot processing of samples from SSF to enzymatic hydrolysis. The comparison of the lignocellulolytic activity profiles of white-rot fungi and brown-rot fungi showed different behaviours. The hierarchical clustering according to glucose and reducing sugars released from each biomass after 72 h enzymatic hydrolysis splits the set of fungal strains into three groups: efficient, no-effect and detrimental-effect species. The efficient group contained 17 species belonging to seven white-rot genera and one brown-rot genus. The yield of sugar released increased significantly (max. 62%) compared with non-inoculated controls for both substrates.     

Differential responses of wood-rot fungi cellulases towards polyclonal antibodies against Trichoderma viride cellobiohydrolase I

Cellobiohydrolase (CBH) I, a main component of Trichoderma extracellular protein, was purified to an electrophoretically homogeneous state from a commercial cellulase preparation (Meicelase from T. viride) by column chromatography on anion and cation exchangers. The difference in the cross-reactivity of cellulolytic enzyme systems of brown-rot and white-rot fungi with the polyclonal antibodies to the CBH I was studied by enzyme-linked immunosorbent assay (ELISA). The antibodies were observed to react quantitatively and with great sensitivity with the antigen (CBH I), and at the same time to cross-react to some extent with T. viride cellulase components other than the CBH I. Nevertheless, the intensity of cross-reactivity of wood-rot fungi cellulases with the antibodies was parallel to the activity of exo-1,4-ß-glucanase. The cellulase system from brown-rot fungi, believed to lack exo-1,4-ß-glucanases, gave a negative response towards the antibodies. These results suggested the presence of some homologous sequences and structures with the T. viride CBH I in the enzymes of white-rot fungi and their absence in those of brown-rot fungi. Correspondence to: M. Ishihara     

Degradation and oligomerization of syringic acid by distinctive ecological groups of fungi

Forty-four terrestrial and aeroaquatic and aquatic fungi, including fifteen species causing white-rot, four species causing brown-rot, and some species causing soft-rot of wood, were tested for their ability to degrade the monomer syringic acid, which is released during decay of angiosperm lignin. None of the white- or brown-rot species caused any detectable degradation of syringic acid under the test conditions; however, six typical white-rot fungi strongly oligomerized syringic acid, both with and without cosubstrate. The main polymerization product was identified as a 1,3-dimethylpyrogallol oligomer by¹³C-NMR. Other minor metabolic products were methylated and hydroxylated derivatives. Oligomerization depended on the presence of 1 or 2 methoxy groups in ortho position to the hydroxy group of the substrate. Among the remaining fungi,Exophiala jeanselmei, Fusarium eumartii, andPaecilomyces variotii completely and rapidly degraded syringic acid (5 g/liter) within 48 to 100 hours. A further seven species were able to degrade syringic acid to some extent when glucose was added. Methylated and demethylated metabolic intermediates were identified by GC/MS.     

The synergistic ability of some wood-degrading fungi to transform lignins and lignosulfonates on various media

Summary In order to investigate the ligninolytic activity with mixed cultures of wood-degrading fungi, and the influence of various growth conditions on this activity, 50 wood-degrading fungi were tested for ligninolysis in pure culture and in pair-wise combinations according to a simple plate test recently developed in this laboratory. It was found that a synergistic degradation of lignin and of lignosulfonate was common among fungi inoculated pair-wise on lignin or lignosulfonate media; decomposition was enhanced in the zone where the two mycelia interacted. This synergistic effect was noted with pairs of two different white-rot fungi, with pairs of one white-rot and one brown-rot fungus, and with pairs of one white-rot and one soil Deuteromycete.Lignosulfonate was more susceptible to the synergistic action of pairs of fungi than was lignin. The synergistic attack on lignosulfonate was more pronounced on a meager medium than on a carbohydrate-rich one. On the contrary, the ligninolysis with pure cultures of the fungi was more pronounced on the carbohydrate-rich medium, and lignin was decomposed more easily than was lignosulfonate.     

Distribution of tetracyclic triterpenoids of lanostane group and sterols in the higher fungi especially of the polyporaceae and related families

The fruit bodies of 97 species of wood-rotting fungi, mainly of Polyporaceae and related families, were examined for the distribution of triterpenes and sterols. Triterpene acids of lanostane group were detected exclusively from the fungi causing brown-rot of woods, while sterols were found to occur commonly in both brown-rot and white-rot fungi. The most abundant sterol was found to be ergosta-7,22-dien-3β-ol. The presence and absence of the triterpene acids is discussed from the point of view of fungal phylogeny.     

Interactions between wood-inhabiting fungi and termites: a meta-analytical review

The foraging behavior and survivorship of termites are modified by the presence of wood-inhabiting fungi. Nonetheless, it is not clear if these interactions are beneficial, negative, or neutral for termites. We conducted a meta-analytical review to determine if the presence of wood-inhabiting fungi affects the foraging behavior and survivorship of termites. Overall, the presence of wood-inhabiting fungi in a resource used by termites was positive, increasing resource consumption by 120%, and aggregation behavior by 81%. The presence of fungi also increased termite trail-following by approximately 200% and increased survival by 136%. The results varied, however, according to the type of fungi evaluated. Decay fungi and sap-stain fungi elicited positive responses in termites, whereas molds did not affect the consumption of cellulose by termites. Amongst the decay fungi group, white-rot fungi caused the strongest and most positive response in all termite behaviors evaluated, although brown-rot fungi is known to be preferred by termites. The results of our study, therefore, suggest that wood-inhabiting fungi are potential facilitators of the foraging behavior and survivorship of termites. These results have great implications for termite biocontrol, as well as for knowledge of the ecological aspects of termite–fungi interactions.     

Effect of carbohydrate and nitrogen on hydrogen peroxide formation by wood decay fungi in solid medium

Abstract Hydrogen peroxide (H₂O₂) has been implicated in degradation of wood by both brown-rot and white-rot fungi. This study found that low concentrations of nitrogem and carbohydrates (cellobiose, glucose, xylose and mannose) in an agar medium had little effect on H₂O₂ production by white-rot fungi. However, low concentrations of nitrogen and carbohydrates stimulated H₂O₂ production by brown-rot fungi. Use of the chromogen 2,2'-azino-di(3-ethyl benzthiazoline-6-sulphonic acid) (ABTS) with horseradish peroxidase to detect H₂O₂ by the fungi was slightly better than detection by the chromogen o -dianisidine with horseradish peroxidase. An auxiliary test to check the role of H₂O₂ in wood decay found that hydrogen peroxide-negative isolates of the white-rot fungi Pharnerochaete chrysosporium and Ganoderma applanatum were unable to decay sweetgum and southern pine.     

Biodelignification of wheat straw by different fungal associations

Seven strains of fungi were tested individually as well as in different combinations to determine their lignin degrading ability using wheat straw as natural substrate. When tested individuallyPhanerochaete chrysosporium caused a maximum loss in total organic matter (26.45%) as well as in the lignin component (28.93%). The associations between different groups: white-rot plus white-rot, white-rot plus brown-rot and white-rot plus soft-rot fungi revealed that in certain combinations the ligninolysis was enhanced to variable extent.Deadalea flavida plusP. chrysosporium was the best association to bring about a lignin loss of 36.27%.     

Vanillic acid metabolism by selected soft-rot,brown-rot,and white-rot fungi

Metabolism of vanillic acid, a product of lignin degradation, has been studied in selected representatives of soft-rot, brown-rot and white-rot fungi. All of the brown-and white-rot species examined decarboxylated vanillate to methoxyhydroquinone oxidatively. Mycelium extracts of all these fungi, except Pleurotus ostreatus contained high levels of an NAD(P)H-dependent vanillate hydroxylase. P. ostreatus also released ¹⁴CO₂ from ¹⁴COOH-vanillate but by a different mechanism possibly involving phenoloxidases. Most of these fungi also contained a dioxygenase which catalysed the intra-diol cleavage of hydroxyquinol (1,2,4-trihydroxybenzene) to form maleylacetate. No 3-O-demethylase activity was detected, and data indicate that in some of the fungi examined cleavage of the aromatic ring occurs without prior removal of the methoxyl group. None of the soft-rot fungi tested contained vanillate hydroxylase or hydroxyquinol 1,2-dioxygenase, but very low levels of protocatechuate 3,4-dioxygenase were detected in mycelium extracts. Vanillate catabolism among members of this group occurs via a different route which may involve ring demethylation although no 3-O-demethylase activity was detected in this study. The enzyme NAD(P)H-quinone oxidoreductase was demonstrated to exist in all the studied groups of fungi.     

Wood durability of home-garden teak against brown-rot and white-rot fungi

Natural decay resistance of teak wood grown in home-garden forestry and the factors influencing decay resistance were determined in comparison with that of a typical forest plantation. Accelerated laboratory tests were conducted on 1800 wood samples drawn from 15 trees of three planted sites. Analysis of variance based on a univariate mixed model showed that planted site, fungal species, and their interaction terms were important sources of variation in decay resistance. With increasing decay resistance from centre to periphery of the heartwood, radial position was a critical factor and the interaction effect of fungal species × radial position was significant in influencing the durability. No significant differences were found in decay resistance either between the opposite radii or due to the various possible interaction terms of radii with the site, fungal species and radial position. There were significant differences in decay resistance against brown-rot fungi between wet and dry sites of home-garden teak although differences against white-rot fungi were non-significant among the three planted sites. Polyporus palustris was the more aggressive brown-rot fungus than Gloeophyllum trabeum. The higher susceptibility of wet site home-garden teak to brown-rot decay was associated with a paler colour of the wood and lower extractive content.     

Protecting wood from mould,decay, and termites with multi-component biocide systems

Biocides must be developed for controlling mould establishment on cellulose-based building materials. Accordingly, biocides intended for indoor applications must be non-toxic, non-volatile, odourless, hypoallergenic, and able to provide long-term protection under conditions of high humidity. Multi-component biocide systems were tested in American Wood-Preservers’ Association soil block tests for inhibition of brown-rot and white-rot decay fungi and American Society for Testing and Materials standard tests for inhibition of mould fungi and termites. Multi-component systems combining a borate base supplemented with either 0.1% azole or 0.5% thujaplicin, performed well against the two brown-rot fungi Postia placenta and Gloeophyllum trabeum; the white-rot fungus Coriolus versicolor; the three mould fungi Aspergillus niger, Penicillium chrysogenum, and Trichoderma viride; and the subterranean termite Reticulitermes flavipes (Kollar). It was concluded that for interior applications borate-based multi-component biocide systems can protect wood from decay fungi, mould fungi, and termites, and that a system containing thiabendazole provided protection at a lower retention than the other biocides in this study. Synergy was observed between the borate base and voriconazole in inhibition of mould.     

A proposed role of oxalic acid in wood decay systems of wood-rotting basidiomycetes

Abstract: The possible roles of oxalic acid, veratryl alcohol, and manganese were investigated in relation to lignin biodegradation by white-rot basidiomycetes. Oxalate inhibited both lignin peroxidase (LiP) and manganese-peroxidase (MnP). and was decarboxylated by the mediation of veratryl alcohol and Mn. Oxalate was shown to regulate the mineralization of lignin in the in vivo system of Phanerochaete chrysosporium . In the brown-rot wood decay process, oxalic acid may serve as an acid catalyst as well as an electron donor for the Fenton reaction, to breakdown cellulose and hemicellulose. Oxaloacetase and glyoxylate oxidase may play a key role in production of oxalic acid by white-rot and brown-rot basidiomycetes such as Phanerochaete chrysosporium, Coriolus versicolor and Tyromyces palustris . A possible role of oxalate metabolism is discussed in relation to the physiology of wood-rotting fungi.     

Ergosterol contents of some wood-rotting basidiomycete fungi grown in liquid and solid culture conditions

Ergosterol contents of six wood-rotting basidiomycetes were analyzed under different cultivation conditions. Four white-rot and two brown-rot fungi were cultivated in liquid synthetic medium with low nutrient nitrogen (2 mM) and 0.1% glucose, and ergosterol in mycelial biomasses were measured weekly for 35 days. The highest ergosterol content per fungal dry mass in the white-rot fungi was found in Phanerochaete chrysosporium being 2100 μg g⁻¹, while in Ceriporiopsis subvermispora it was 1700 μg g⁻¹, Phlebia radiata 700 μg g⁻¹, and Physisporinus rivulosus 560 μg g⁻¹. In brown-rot fungi the ergosterol content was in Poria placenta 2868 μg g⁻¹ and in Gloeophyllum trabeum 3915 μg g⁻¹. On agar media, P. chrysosporium and P. radiata reached the highest ergosterol value in 7 days, while in wood block cultures the ergosterol contents were quite stable. The conversion factors for ergosterol-to-fungal biomass varied from 48 and 243, which were lower than values for ascomycetous soil fungi reported in the literature.     

Efficacy of tar oil recovered during slow pyrolysis of macadamia nut shells

Decay and termite resistance of wood treated with tar oil obtained from a commercial pyrolysis process of macadamia nut shells was evaluated. Vacuum-treated pinewood specimens were subjected to two brown- and two white-rot fungi based on the soil-block test method specified by the American Wood Protection Association after a 10-day-leaching process. Treated specimens were also subjected to the subterranean termite attack according to Japanese Industrial Standards (JIS) for 3 weeks under laboratory conditions. In the study, growth inhibition of selected fungi with the tar oil was also tested in vitro. Treated wood specimens at a retention level of 460 kg m⁻³ showed good protection against all the fungi tested. Mass losses in leached specimens were less than those observed in unleached specimens. Similar results were seen when the specimens were subjected to termite attack. Inhibition tests showed that higher concentrations of the tar oil are critical for inhibition of the brown-rot fungi compared to the concentrations required to impede the white-rot and sap-staining fungi tested.     

Label-free differentially proteomic analysis of interspecific interaction between white-rot fungi highlights oxidative stress response and high metabolic activity

The laccase production by mycelial antagonistic interaction among white-rot fungi is a very important pathway for lignin degradation research. To gain a better understanding of competitive mechanisms under mycelial antagonistic interaction among three lignin-degrading white-rot basidiomycetes of Trametesversicolor (Tv), Pleurotusostreatus (Po) and Dichomitussqualens (Ds), mycelial morphology and proteins in three co-culture combinations TvPo (Tv cocultivated with Po), PoDs (Po cocultivated with Ds), TvDs (Tv cocultivated with Ds) were compared with corresponding each two mono-cultures. In this study, scanning electron microscopy detection of co-cultures indicated a highly close attachment of fungal hyphae with each other and conidiation could be inhibited under fungal interaction. In addition, a label-free proteomic analysis revealed changes on fungal proteomes existed in their counterpart competitors of co-culture. The maximum number of 1020 differentially expressed proteins (DEPs) were identified in PoDs relative to Po while the minimum number of 367 DEPs were identified in PoDs relative to Ds. Notably, we also found a large number of overexpressed proteins were oxidative stress-related proteins, followed by carbohydrate metabolism-related proteins and energy production-related proteins in all three co-culture combinations compared with control. These results were important for the future exploration of molecular mechanisms underlying lignin-degrading fungal interaction.     

Deadwood substrate and species-species interactions determine the release of volatile organic compounds by wood-decaying fungi

Wood-decaying fungi in the phylum Basidiomycota play a significant role in the global carbon cycle, as they decompose deadwood effectively. Fungi may compete for utilizable substrate and growth space by producing soluble metabolites and by releasing volatile organic compounds (VOCs). We determined the role of wood substrate (Scots pine or Norway spruce) on the generation of hyphal biomass, secreted metabolites and enzyme activities, wood decomposition rate, and fungal species-species interactions on VOC release. We studied one brown-rot species (Fomitopsis pinicola) and two white-rot species (Phlebia radiata and Trichaptum abietinum) cultivated individually or in combinations. Wood substrate quality influences VOC release by the wood-decaying fungi, with signature differences caused by the decomposition trait (brown rot or white rot) and species-species interactions. VOC release was higher in the cultures of Basidiomycota than in uncolonized sawdust. Fungal biomass, decomposition activity, iron reduction, enzyme activities, oxalate anion content, and oxalic acid production explained VOC release from decaying wood.     

Evaluation of accelerated decay of wood plastic composites by Xylophagus fungi

The resistance to fungal attack of wood plastic composites (WPCs) containing 40% polypropylene and 60% either pine, maple or oak, wt%/wt%, was examined. WPCs specimens were made using the hot press system. Resistance to decay was evaluated using soil block and agar tests. Test specimens were exposed to either white-rot fungi, Trametes versicolor or Phanerochaete chrysosporium, or the brown-rot fungi Gloeophyllum trabeum or Postia placenta for six or 12 weeks. Moisture content and weight loss were used to assess the extent of decay of WPCs. Rates of decay in WPCs exposed in soil-block tests were greater than those exposed in the agar. WPCs containing either maple or oak were more susceptible to fungal attack then those containing pine.