Determination of optimal growth parameters for the bioincising fungus Physisporinus vitreus by means of response surface methodology

Aim:  To evaluate the influence of water activity ( a _w), temperature and pH on the radial growth and lag phase of Physisporinus vitreus (E-642), a basidiomycete was used in the biotechnological process of bioincising.
Methods and Results:  Radial growth was monitored for 20 days on malt extract agar medium. Five levels of a _w (0·998, 0·982, 0·955, 0·928, 0·892) were combined with three incubation temperatures (10, 15, 20°C) and three pH values (4, 5, 6). Data analyses showed a highly significant effect of a _w and temperature ( P <  0·0001) and a significant effect of pH ( P <  0·05). The radial growth rate and lag phase of P. vitreus were very sensitive to a _w reduction. Although P. vitreus was able to grow at all the selected temperatures and pH values, the lag phase increased with decreasing a _w and growth became inhibited at a _w = 0·955. Optimal conditions for growth of P. vitreus were a _w = 0·998, 20°C and pH 5. The response surface model provided reliable estimates of these growth parameters and confirmed a greater dependence on a _w than on temperature or pH under in vitro conditions.
Conclusions:  Low levels of a _w can prevent growth of P. vitreus , so wood moisture content should be adjusted accordingly.
Significance and Impact of the Study:  Implementation of these results should contribute towards the optimization and efficiency of bioincising.     

Resistance of bioincised wood treated with wood preservatives to blue-stain and wood-decay fungi

Bioincising is a biotechnological process that aims at the improvement of wood preservative uptake in wood species with a low permeability, such as Norway spruce (Picea abies (L.) Karst). The process is based on a short-term pre-treatment with white-rot fungus Physisporinus vitreus. During incubation the membranes of bordered and half bordered pits are supposed to be degraded by fungal activity resulting in a better treatability of the wood structure for wood preservatives. In the present study, first of all the resistance of bioincised Norway spruce heartwood and untreated controls against blue-stain and wood-decay fungi (white- and brown-rot) was determined. Then, bioincised and untreated specimens were dipped or vacuum impregnated with six wood preservatives and substance uptake was assessed gravimetrically. Additionally, the penetration of 3-iodo-2-propynyl butylcarbamate (IPBC) into the wood was analyzed by high-pressure liquid chromatography (HPLC). Finally, wood resistance was assessed according to the European standards EN 152 and EN 113. Results showed no difference between bioincised wood without preservatives and the untreated wood against blue-stain discolouration. However, a significant (P < 0.05) increase in susceptibility against wood decay was recorded. In the bioincised wood samples a significantly higher uptake of all the different preservatives was determined and the HPLC-method revealed that IPBC penetrated deeper into bioincised wood than into control samples. The improved uptake of preservatives into bioincised wood resulted in a significantly higher resistance against white- and brown-rot fungi. However, only a slight protection against wood discolouration by blue-stain fungi was recorded. The results of this study show for the first time that the biotechnological process with P. vitreus can be used to improve wood durability by increasing the uptake and penetration of wood preservatives.     

New polymeric model substrates for the study of microbial ligninolysis.

Lignin model dimers are valuable tools for the elucidation of microbial ligninolytic mechanisms, but their low molecular weight (MW) makes them susceptible to nonligninolytic intracellular metabolism. To address this problem, we prepared lignin models in which unlabeled and alpha-14C-labeled beta-O-4-linked dimers were covalently attached to 8,000-MW polyethylene glycol (PEG) or to 45,000-MW polystyrene (PS). The water-soluble PEG-linked model was mineralized extensively in liquid medium and in solid wood cultures by the white rot fungus Phanerochaete chrysosporium, whereas the water-insoluble PS-linked model was not. Gel permeation chromatography showed that P. chrysosporium degraded the PEG-linked model by cleaving its lignin dimer substructure rather than its PEG moiety. C alpha-C beta cleavage was the major fate of the PEG-linked model after incubation with P. chrysosporium in vivo and also after oxidation with P. chrysosporium lignin peroxidase in vitro. The brown rot fungus Gloeophyllum trabeum, which unlike P. chrysosporium lacks a vigorous extracellular ligninolytic system, was unable to degrade the PEG-linked model efficiently. These results show that PEG-linked lignin models are a marked improvement over the low-MW models that have been used in the past.     

Characteristics of Wood Structure in Gymnosperms and Their systematic Significance

The systematic positions and taxonomic ranks of orders and families in Gymnosperms, especially those in Coniferopsida, are analysed and discussed in this paper based on the evolutionary trends in the wood structure. The opinions of the present authors are as follow: 1. The separation of the Araucariaceae from the Coniferae and establishment of the Araucariales are reasonable,because the intertracheid pitting in the wood is the Araucarioid type and there are no pits on both horizontal and end walls of ray parenchyma cells in the family. 2. The position of the genus Ginkgo in Cheng’s system is acceptable. Ginkgo is more similar to Coniferae than to Cycadaceae in the wood structure. 3. According to the characteristics of wood structure, arrangement of the Podocarpaceae, Cephalotaxaceae and Taxaceae between the Araucariaceae and the Pinaceae is reasonable. Among these families, the Cephalotaxaceae and Taxaceae are more closely related to each other in the view of the spiral thickenings which often appear on the inner wall of wood tracheids. 4. Further evidence for the establishment of the Sciadopitysaceae is provided. For example, most of cross-field pits in the wood of the Sciadopitysaceae are window like, while some of them are of the Lemon type or the Subtaxodioid type; bordered pits are of the Araucaria B type. 5. The characteristics of wood structure in the genus Platycladus differ greatly from Thuja. The former has cross field pits of the Cupressoid type, bordered pits of Araucaria B type and warty layer on the inner surface of tracheids. All of these characteristics have added further evidence for the separation of Platycladus from Thuja. 6. Based on the structural characteristics of woody rays in the Pinaceae, the most primitive genera are Abies, Keteleeria and Pseudolarix, while more advanced ones are Cedrus and Tsuga, and even more advanced ones are Pseudotsuga, Cathaya, Picea and Larix, all of which share normal resin canals. The most advanced genus is Pinus which is also of normal resin canals. Pinus can be divided into three subgenera, Haploxylon, Parry and Diploxylon, according to the presence or absence of dentation and warty layer in wood tracheids. 7. It is reasonable to place the genus Amentotaxus in the Taxaceae, because membrane of bordered pits in the genus is similar to that in the other four genera of the Taxaceae, both of the Araucaria type. 8. The present authors agree with Cheng’s (1978) treatment of Sect. Heopeuce in Tsuga, based on the fact that Tsuga longibracteata has traumatic resin canals and warty layer. Reducing Pinus hwangshanensis into P. taiwanensis, made by Cheng, is reasonable because of the similarities between P. hwangshanensis and P. taiwanensis in the wood structure. The establishment of a new subgenus, Patty, for Pinus bungeana is suitable based on chemotaxonomy, morphology and the distinct warty layer on the innersurface of wood tracheids.     

辽西义县下白垩统沙海组木化石新材料

辽西地区下白垩统沙海组是我国北方地区重要的白垩纪木化石产出层位,其产出的木化石数量丰富、类型多样.尽管前人开展了部分研究,但目前对沙海组木化石植物群组成特征的认识仍相对薄弱.本文报道了辽西义县上石洞沟地区沙海组产出的木化石新材料,共鉴定出2属3种,分别为:Phyllocladoxylon cf.eboracense(H...     

Influence of tropolone on Poria placenta wood degradation

Fenton reactions are believed to play important roles in wood degradation by brown rot fungi. In this context, the effect of tropolone (2-hydroxycyclohepta-2,4,6-trienone), a metal chelator, on wood degradation by Poria placenta was investigated. Tropolone (50 micro M) strongly inhibits fungal growth on malt agar, but this inhibition could be relieved by adding iron salts. With an experimental system containing two separate parts, one supplemented with tropolone (100 micro M) and the other not, it was shown that the fungus is able to reallocate essential minerals from the area where they are available and also to grow in these conditions on malt-agar in the presence of tropolone. Nevertheless, even in the presence of an external source of metals, P. placenta is not able to attack pine blocks impregnated with tropolone (5 mM). This wood degradation inhibition is related to the presence of the tropolone hydroxyl group, as shown by the use of analogs (cyclohepta-2,4,6-trienone and 2-methoxycyclohepta-2,4,6-trienone). Furthermore, tropolone possesses both weak antioxidative and weak radical-scavenging properties and a strong affinity for ferric ion and is able to inhibit ferric iron reduction by catecholates, lowering the redox potential of the iron couple. These data are consistent with the hypothesis that tropolone inhibits wood degradation by P. placenta by chelating iron present in wood, thus avoiding initiation of the Fenton reaction. This study demonstrates that iron chelators such as tropolone could be also involved in novel and more environmentally benign preservative systems.     

STUDIES OF WOOD-DESTROYING FUNGI I. POLYPOBUS HISPIDUS (FRIES)

The characteristics of the Polyporus Msjndus , when grown on artificial media, both solid and liquid, are described and compared with those given by Baxter.
Growth on wood of ash under laboratory conditions produces a rot which is indistinguishable from that occurring naturally. The distribution of the hyphae in the wood is described.
The mode of penetration of the cell-wall by the hyphae is figured. It is apparently by pits in the early stages of decay, but by bore-holes, formed entirely by enzyme activity, in-the more advanced rot.
The rate of growth of the fungus under controlled conditions has been measured, and shown to be 0–5 cm. per month.
Successful inoculation experiments have been carried out with young trees, confirming the results of Baxter, who states that the fungus can attack young, living sap wood.
An investigation of the enzymes produced by the mycelium has been carried out, and a method evolved for demonstrating the presence of a ligninase. This is a modification of Czapek's "hadromal" reaction.
The following enzymes are shown to be present in the mycelium: emulsin, diastase, invertase, ligninase, hemicellulase, oxidase, and catalase. The list is not intended to be exhaustive.
The writer desires to express his thanks to Mr W. R. Day, of the Imperial Forestry Institute, Oxford, and to Dr W. Brown, of the Royal College of Science, for helpful criticism and advice. Also to Mr R. S. Pearson, C.I.E., F.L.S., the Director of Forest Products Research, for permission to publish this paper.     

<Emphasis Type="Italic">Physisporinus vitreus</Emphasis>: a versatile white rot fungus for engineering value-added wood products

The credo of every scientist working in the field of applied science is to transfer knowledge “from science to market,” a process that combines (1) science (fundamental discoveries and basic research) with (2) technology development (performance assessment and optimization) and (3) technology transfer (industrial application). Over the past 7 years, we have intensively investigated the potential of the white rot fungus, Physisporinus vitreus, for engineering value-added wood products. Because of its exceptional wood degradation pattern, i.e., selective lignification without significant wood strength losses and a preferential degradation of bordered pit membranes, it is possible to use this fungus under controlled conditions to improve the acoustic properties of tonewood (i.e., “mycowood”) as well as to enhance the uptake of preservatives and wood modification substances in refractory wood species (e.g., Norway spruce), a process known as “bioincising.” This minireview summarizes the research that we have performed with P. vitreus and critically discusses the challenges encountered during the development of two distinct processes for engineering value-added wood products. Finally, we peep into the future potential of the bioincising and mycowood processes for additional applications in the forest and wood industry.     

Influence of Tropolone on Poria placenta Wood Degradation

Fenton reactions are believed to play important roles in wood degradation by brown rot fungi. In this context, the effect of tropolone (2-hydroxycyclohepta-2,4,6-trienone), a metal chelator, on wood degradation by Poria placenta was investigated. Tropolone (50 μM) strongly inhibits fungal growth on malt agar, but this inhibition could be relieved by adding iron salts. With an experimental system containing two separate parts, one supplemented with tropolone (100 μM) and the other not, it was shown that the fungus is able to reallocate essential minerals from the area where they are available and also to grow in these conditions on malt-agar in the presence of tropolone. Nevertheless, even in the presence of an external source of metals, P. placenta is not able to attack pine blocks impregnated with tropolone (5 mM). This wood degradation inhibition is related to the presence of the tropolone hydroxyl group, as shown by the use of analogs (cyclohepta-2,4,6-trienone and 2-methoxycyclohepta-2,4,6-trienone). Furthermore, tropolone possesses both weak antioxidative and weak radical-scavenging properties and a strong affinity for ferric ion and is able to inhibit ferric iron reduction by catecholates, lowering the redox potential of the iron couple. These data are consistent with the hypothesis that tropolone inhibits wood degradation by P. placenta by chelating iron present in wood, thus avoiding initiation of the Fenton reaction. This study demonstrates that iron chelators such as tropolone could be also involved in novel and more environmentally benign preservative systems.     

Characterization and expression of a myosin heavy–chain isoform in juvenile walleye Sander vitreus

In this study, myosin, the major component of myofibrillar protein in the skeletal muscle, was characterized and its expression was monitored during growth in juvenile walleye Sander vitreus. First, the coding region of myosin heavy chain (MyHC) from the fast skeletal muscle of walleye was amplified by long-distance PCR using a full-length cDNA. Phylogenetic analysis was used to determine the evolutionary relationship of this S. vitreus myosin sequence to other vertebrate myosin sequences. Next, it was established that the myosin isoform was most prevalent in the white muscle, compared with the red and cardiac muscle. Myosin expression was monitored over a series of experiments designed to influence growth. Specifically, change in MyHC mRNA was monitored after acute changes in feeding. Fish exposed to a one-week fasting period showed significant decreases in MyHC mRNA levels by the end of the fast. The effect of feeding was also examined more closely over a 24 h period after feeding, but results showed no significant change in myosin expression levels through this time period. Finally, fish with higher growth rates had higher MyHC mRNA and protein expression levels. This study indicates that MyHC mRNA expression is sensitive to the factors that may influence growth in juvenile S. vitreus .     

Tetracentron Wood from the Miocene of Noto Peninsula,Central Japan,with a short revision of homoxylic fossil woods

A vesselless fossil wood was discovered in the Miocene Yanagida Formation in the Noto Peninsula, central Japan. This fossil has distinct growth rings with gradual transition from the early- to the latewood ; tracheids, which are called 'usual traeheids' here, constitute the ground mass of the wood and have typical scalariform bordered pits on radial walls in the earlywood and circular sparse pits on those in the latewood ; rays are 1\2-4 cells wide and heterogeneous with low to high uniseriate wings; axial parenchyma strands are scattered in the latewood. This wood has a peculiar feature; sporadic radial files of broad tracheids whose tangential walls have crowded alternate bordered pits. The radial walls have crowded half-bordered pits to ray cells, but no pits to the usual tracheids. Among all of the extant and extinct angiosperms and gymnosperms, these unusual tracheids occur only in Tetracentron. From these features, we refer the fossil to the extant genus Tetracentron, and name it T. japonoxylum. A revision of homoxylic woods is made for comparision with the present fossil. Tetracentron japonoxylum is the only fossil wood of Tetracentron.     

Inhibitory Effect of <i>N</i>, <i>N</i>-Dimethylhexadecylamine on the Growth of White-Rot Fungus <i>Trametes versicolor</i> (L.) in Wood

Wood is an organic material that is a source of carbon of organisms called Wood-decay fungi, and to preserve the wood, various toxic compounds to man and the environment have been used. To analyze the effect of N,N-Dimethylhexadecylamine (DMHDA) on wood attacked by the rotting fungus Trametes versicolor L. We used an in vitro system to expose the fungus T. versicolor to different concentrations of the DMHDA (50, 150 and 450 μM). We quantified the diameter of mycelial growth and laccase activity, also, under these experimental conditions we studied morphological details of the organisms using different scanning equipment including scanning electron microscopy. The growth of T. versicolor exposed to DMHDA for 60 days, showed a concentration-dependent dose behavior, also, the electron microscopy analysis revealed that the morphology and mycelial density was affected by the DMHDA, showing a formation of atypical morphological and thickener folds. Finally, the pieces of wood treated with DMHDA and exposed to the fungus had a lower mass loss, after a period of 60 days of exposure, the values obtained were 0.7, 1.0 and 0.5 g of mass lost for the control, LoC and LoDMHDA treatments respectively. Wood-rot fungi have represented economic losses worldwide, the strategies used have been supported by toxic compounds for the environment. The DMHDA both in the Petri dish system and as a wood preservative was shown to significantly inhibit the growth of T. versicolor.     

An NADH:quinone oxidoreductase active during biodegradation by the brown-rot basidiomycete Gloeophyllum trabeum

The brown-rot basidiomycete Gloeophyllum trabeum uses a quinone redox cycle to generate extracellular Fenton reagent, a key component of the biodegradative system expressed by this highly destructive wood decay fungus. The hitherto uncharacterized quinone reductase that drives this cycle is a potential target for inhibitors of wood decay. We have identified the major quinone reductase expressed by G. trabeum under conditions that elicit high levels of quinone redox cycling. The enzyme comprises two identical 22-kDa subunits, each with one molecule of flavin mononucleotide. It is specific for NADH as the reductant and uses the quinones produced by G. trabeum (2,5-dimethoxy-1,4-benzoquinone and 4,5-dimethoxy-1,2-benzoquinone) as electron acceptors. The affinity of the reductase for these quinones is so high that precise kinetic parameters were not obtainable, but it is clear that k(cat)/K(m) for the quinones is greater than 10(8) M(-1) s(-1). The reductase is encoded by a gene with substantial similarity to NAD(P)H:quinone reductase genes from other fungi. The G. trabeum quinone reductase may function in quinone detoxification, a role often proposed for these enzymes, but we hypothesize that the fungus has recruited it to drive extracellular oxyradical production.     

Growth of Arthrobotrys superba from a birch wood resource base into soil determined by radioactive tracing

The ability of a nematode-trapping fungus to establish in field soil is an important characteristic when considering its use as a biological control agent. The outgrowth of the nematode-trapping fungus Arthrobotrys superba from wood was recorded by labelling the fungus with [(14)C]3-O-methylglucose and [(32)P]orthophosphoric acid and by using the soil sprinkling method. The fungus reached a distance of 7-8 cm during 25 days in heat-treated (60 degrees C) soil, detected by either radioactive tracing or the soil sprinkling technique. The two labelled compounds were co-distributed at all sampling times (r(2)=0.946) which indicates that the glucose pool (as methylglucose) and phosphorus content were correlated throughout the mycelium. In natural, non-heat-treated soil the fungus reached a distance of 1.5 cm from one disc of birch wood after 30 days, while it reached 3.2 cm during the same period when the food base was a pile of five inoculated discs. The experiments showed, for the first time, that a nematophagous fungus, A. superba, can grow out into soil from a piece of wood and supported by nutrients translocated from the resource base to the edge of the mycelium.     

Comparative genomics of the white-rot fungi, Phanerochaete carnosa and P. chrysosporium, to elucidate the genetic basis of the distinct wood types they colonize

ABSTRACT: BACKGROUND: Softwood is the predominant form of land plant biomass in the Northern hemisphere, and is among the most recalcitrant biomass resources to bioprocess technologies. The white rot fungus, Phanerochaete carnosa, has been isolated almost exclusively from softwoods, while most other known white-rot species, including Phanerochaete chrysosporium, were mainly isolated from hardwoods. Accordingly, it is anticipated that P. carnosa encodes a distinct set of enzymes and proteins that promote softwood decomposition. To elucidate the genetic basis of softwood bioconversion by a white-rot fungus, the present study reports the P. carnosa genome sequence and its comparative analysis with the previously reported P. chrysosporium genome. RESULTS: P. carnosa encodes a complete set of lignocellulose-active enzymes. Comparative genomic analysis revealed that P. carnosa is enriched with genes encoding manganese peroxidase, and that the most divergent glycoside hydrolase families were predicted to encode hemicellulases and glycoprotein degrading enzymes. Most remarkably, P. carnosa possesses one of the largest P450 contingents (266 P450s) among the sequenced and annotated wood-rotting basidiomycetes, nearly double that of P. chrysosporium. Along with metabolic pathway modeling, comparative growth studies on model compounds and chemical analyses of decomposed wood components showed greater tolerance of P. carnosa to various substrates including coniferous heartwood. CONCLUSIONS: The P. carnosa genome is enriched with genes that encode P450 monooxygenases that can participate in extractives degradation, and manganese peroxidases involved in lignin degradation. The significant expansion of P450s in P. carnosa, along with differences in carbohydrate- and lignin-degrading enzymes, could be correlated to the utilization of heartwood and sapwood preparations from both coniferous and hardwood species.     

Inoculum production of the ectomycorrhizal fungus Pisolithus microcarpus in an airlift bioreactor

Many important tree species in reforestation programs are dependent on ectomycorrhizal symbiosis in order to survive and grow, mainly in poor soils. The exploitation of this symbiosis to increase plant productivity demands the establishment of inoculum production methods. This study aims to propose an inoculum production method of the ectomycorrhizal fungus Pisolithus microcarpus (isolate UFSC-Pt116) using liquid fermentation in an airlift bioreactor with external circulation. The fungus grew as dark dense pellets during a batch fermentation at 25.5 degrees C and air inlet of 0.26-0.43 vvm. The maximum biomass (dry weight) achieved in the airlift bioreactor was approximately 5 g.l(-1) after 10-11 days. The specific growth rate (micro(x)) in the exponential phase was 0.576 day(-1), the yield factor (Y(X/S)) 0.418, and the productivity (P(X)) 0.480 g.l(-1).day(-1). This specific growth rate was higher than that observed by other authors during fermentation processes with other Pisolithus isolates. The method seems to be very suitable for biomass production of this fungus. However, new studies on the fungus growth morphology in this system, as well as on the efficiency of the process for the cultivation of other ectomycorrhizal fungi, are necessary. It is also necessary to test the infectivity and efficiency of the inoculum towards the hosts.     

Antrodia gossypium,Phlebiopsis gigantea and Heterobasidion parviporum: in vitro growth and Norway spruce wood block decay

Polymerase chain reaction-amplified and sequenced isolates of Antrodia gossypium, Phlebiopsis gigantea and Heterobasidion parviporum from decaying Norway spruce wood blocks after three and six months, which exhibited linear growth, were investigated. P. gigantea strains showed the fastest growth, whereas A. gossypium growth was five times slower. The differences between the mean daily increment of A. gossypium and the other examined isolates (except Hp2) were statistically significant. There were also significant differences in wood decay between densities over time. These results were confirmed by the decay acceleration index (DAI) and decay activity index, which were positively correlated with wood density regardless of the fungus species. The registered P. gigantea strains (Rotstop and PG Suspension) exhibited a strong decomposition ability (28% after six months); the weight loss caused by A. gossypium after six months of decay (15.2%) was similar to the results of P. gigantea (GB) after just three months (13.2%). All tested H. parviporum isolates showed rather rapid growth and equally strong wood decay (20–25%) compared to those of P. gigantea. DAI showed that A. gossypium may significantly contribute to wood decomposition over time, particularly in less dense wood samples. The use of both saprotrophs as biological agents against root pathogens is discussed.     

An anamorph of the white-rot fungus Bjerkandera adusta capable of colonizing and degrading compact disc components

A Geotrichum-like fungus isolated from a biodeteriorated compact disc (CD) was able to degrade in vitro the components of different CD types. The fungal hyphae inside the CD fragments grew through the aluminium layer and produced the solubilization of this metal. Furthermore, examination of CDs by scanning electron microscopy showed that the fungus was able to destroy the pits and lands structures grooved in the polycarbonate layer, confirming degradation of this aromatic polymer. The fungus secretes aryl-alcohol oxidase and Mn2+-oxidizing peroxidase, two kinds of oxidoreductases characteristic of ligninolytic basidiomycetes. Analysis of the ITS region of ribosomal DNA, as well as the morphological characteristics, the lack of sexual forms and the profile of enzymes secreted in liquid medium identified the fungus as a Geotrichum-like anamorph of Bjerkandera adusta (Willd.) P. Karst.     

Paint Deterioration as a Result of the Growth of Aureobasidium pullulans on Wood

Growth of Aureobasidium was noted on both painted and unpainted wood surfaces but not on painted glass slides, indicating that the source of carbon and energy for growth was not associated with paint components but was probably supplied by the wood. Several aromatic compounds related to aromatic extractives of wood were shown to support growth of this fungus.     

Multidimensional NMR analysis reveals truncated lignin structures in wood decayed by the brown rot basidiomycete Postia placenta

Lignocellulose biodegradation, an essential step in terrestrial carbon cycling, generally involves removal of the recalcitrant lignin barrier that otherwise prevents infiltration by microbial polysaccharide hydrolases. However, fungi that cause brown rot of wood, a major route for biomass recycling in coniferous forests, utilize wood polysaccharides efficiently while removing little of the lignin. The mechanism by which these basidiomycetes breach the lignin remains unclear. We used recently developed methods for solubilization and multidimensional (1) H-(13) C solution-state NMR spectroscopy of ball-milled lignocellulose to analyse aspen wood degraded by Postia placenta. The results showed that decay decreased the content of the principal arylglycerol-β-aryl ether interunit linkage in the lignin by more than half, while increasing the frequency of several truncated lignin structures roughly fourfold over the level found in sound aspen. These new end-groups, consisting of benzaldehydes, benzoic acids and phenylglycerols, accounted for 6-7% of all original lignin subunits. Our results provide evidence that brown rot by P. placenta results in significant ligninolysis, which might enable infiltration of the wood by polysaccharide hydrolases even though the partially degraded lignin remains in situ. Recent work has revealed that the P. placenta genome encodes no ligninolytic peroxidases, but has also shown that this fungus produces an extracellular Fenton system. It is accordingly likely that P. placenta employs electrophilic reactive oxygen species such as hydroxyl radicals to disrupt lignin in wood.