Characterisation of Postia placenta colonisation during 36 weeks in acetylated southern yellow pine sapwood at three acetylation levels including genomic DNA and gene expression quantification of the fungus

One way to protect timber in service against basidiomycete deterioration is by means of acetylation via reaction with acetic anhydride. The reason why acetylated wood (WAc) is resistant against decay fungi is still not exactly understood. The aim of this study was to contribute to this field of science, and Postia placenta colonisation after 4, 12, 20, 28 and 36 weeks was observed at Three acetylation levels of Pinus spp. sapwood. Mass loss (ML) and wood moisture content (MC) data reflected the acetylation levels. The initial equilibrium MC (EMC) proved to be a good indicator of subsequent ML. Genomic DNA quantification showed P. placenta colonisation in all samples, also in samples where no ML were detectable. The number of expressed gene transcripts was limited, but the findings supported the results of previous studies: WAc seems to have some resistance against oxidative mechanisms, which are part of the metabolism of P. placenta. This leads to a delay in decay initiation, a delay in Expression of genes involved in enzymatic depolymerisation, and a slower decay rate. The magnitudes of these effects are presented for each acetylation level. The data also imply that there is no absolute decay threshold at high acetylation levels, but instead a significant delay of decay initiation and a slower decay rate.publishedVersio

Initial Rhodonia placenta Gene Expression in Acetylated Wood: Group-Wise Upregulation of Non-Enzymatic Oxidative Wood Degradation Genes Depending on the Treatment Level

Acetylation has been shown to delay fungal decay, but the underlying mechanisms are poorly understood. Brown-rot fungi, such as Rhodonia placenta (Fr.) Niemelä, K.H. Larss. & Schigel, degrade wood in two steps, i.e., oxidative depolymerization followed by secretion of hydrolytic enzymes. Since separating the two degradation steps has been proven challenging, a new sample design was applied to the task. The aim of this study was to compare the expression of 10 genes during the initial decay phase in wood and wood acetylated to three different weight percentage gains (WPG). The results showed that not all genes thought to play a role in initiating brown-rot decay are upregulated. Furthermore, the results indicate that R. placenta upregulates an increasing number of genes involved in the oxidative degradation phase with increasing WPG

Incipient brown rot decay in modified wood : patterns of mass loss, structural integrity, moisture and acetyl content in high resolution

The study of degradation and growth patterns of fungi in modified wood may increase the understanding of their mode of action and may lead to more accurate service-life predictions. The aim of this paper was to study the degradation and growth patterns of brown rot fungi in modified wood and to measure moisture content (MC), structural integrity and the acetyl content by frequent monitoring over 300 days. Mass loss (ML) in the modified wood materials increased slowly up to 3% for 50–100 days after which it flattened out and remained constant during the remainder of the test. Structural integrity and acetyl content were maintained in the modified wood materials and MC was lower compared to untreated wood throughout the decay test. ML results of untreated wood indicate that fungi in solid wood go through distinct phases; the degradation patterns in the modified wood materials were more difficult to interpret

Sustainability Assessment in Product Development: Experiences from Two Projects

The poster describes how sustainability is assessed in product development, drawing from experiences of two on-going projects: WoodLife and CelluNova. The objective of WoodLife is to improve properties and increase service-life of clear coatings and adhesives for wood, and hence widen wood product’s scope of application. If this allows wood to replace energy-intensive materials or materials of fossil origin (e.g. aluminium or PVC in window frames, respectively), there is a potential to, for example, decrease greenhouse gas emissions. In CelluNova, the aim is to develop dissolving and spinning conditions which facilitate integration of textile fiber production into pulp mills. This has the potential to be environmentally beneficial compared to today’s pulp-based textile fibers (e.g. viscose). It can also enhance the competitiveness of pulp-based textile fibers compared with today’s market-dominating alternatives: cotton and polyester fibers – fibers subject to environmental concerns and possibly future supply issues due to an anticipated rise in global textile demand. Both projects can potentially expand the forest’s role in solving the resource problems of tomorrow and contribute to a more sustainable society. But unless sustainability parameters are monitored during product development, new unwanted sustainability issues may be introduced along the way. The assessment is founded on the methodology of life cycle assessment, social life cycle assessment and life cycle costing, reflecting the environmental, social and economic dimensions of sustainability, respectively. Five main challenges have been identified: communication, definition of sustainability, underdeveloped methodology, non-existence of production processes and comparison of inherently different dimensions. In the poster, these challenges are elucidated along with experiences of various approaches to tackle them. For example, an exercise on rating different indicators of social sustainability has been carried out within CelluNova. This turned out to be valuable in addressing three of the identified challenges: communication, definition of sustainability and underdeveloped methodology

Combined evaluation of durability and ecotoxicity: a case study on furfurylated wood

Modified wood is commercially available and merchandized as a new, environmentally friendly and durable wood species. However, there are no standards focusing on the evaluation of modified wood. Combining resistance against fungal decay and good ecotoxicological properties may be a start. In this study softwood and hardwood species were furfurylated using different treatment processes and treating solutions. The durability was determined by exposing the treated wood to a range of Basidiomycetes and the ecotoxicity was studied on two aquatic organisms. It was the purpose to come to a strategy for how to unite efficacy and ecotoxicity, since this is important in product development. The results show that the selection of fungus used for mass loss determination and the choice of ecotoxicity method is decisive, confirming that a combination of methods is valuable. A tiered approach to find the optimal treatment seems the best option. First, adequate protection against woodrotting fungi should be attained, followed by ecotoxicity evaluation of the wood leachates. If necessary, the optimization process should be repeated until both durability and ecotoxicity are within satisfactory limits. This process could be extended with other evaluation criteria, e.g. dimensional stability of the modified wood or a risk analysis of its leachate

Hydrophobic and Hydrophilic Extractives in Norway Spruce and Kurile Larch and Their Role in Brown-Rot Degradation

Extractives found in the heartwood of a moderately durable conifer (Larix gmelinii var. japonica) were compared with those found in a non-durable one (Picea abies). We identified and quantified heartwood extractives by extraction with solvents of different polarities and gas chromatography with mass spectral detection (GC-MS). Among the extracted compounds, there was a much higher amount of hydrophilic phenolics in larch (flavonoids) than in spruce (lignans). Both species had similar resin acid and fatty acid contents. The hydrophobic resin components are considered fungitoxic and the more hydrophilic components are known for their antioxidant activity. To ascertain the importance of the different classes of extractives, samples were partially extracted prior to subjection to the brown-rot fungus Rhodonia placenta for 2–8 weeks. Results indicated that the most important (but rather inefficient) defense in spruce came from the fungitoxic resin, while large amounts of flavonoids played a key role in larch defense. Possible moisture exclusion effects of larch extractives were quantified via the equilibrium moisture content of partially extracted samples, but were found to be too small to play any significant role in the defense against incipient brow-rot attack

Degradative Capacity of Two Strains of Rhodonia placenta: From Phenotype to Genotype

Brown rot fungi, such as Rhodonia placenta (previously Postia placenta), occur naturally in northern coniferous forest ecosystems and are known to be the most destructive group of decay fungi, degrading wood faster and more effectively than other wood-degrading organisms. It has been shown that brown rot fungi not only rely on enzymatic degradation of lignocellulose, but also use low molecular weight oxidative agents in a non-enzymatic degradation step prior to the enzymatic degradation. R. placenta is used in standardized decay tests in both Europe and North America. However, two different strains are employed (FPRL280 and MAD-698, respectively) for which differences in colonization-rate, mass loss, as well as in gene expression have been observed, limiting the comparability of results. To elucidate the divergence between both strains, we investigated the phenotypes in more detail and compared their genomes. Significant phenotypic differences were found between the two strains, and no fusion was possible. MAD-698 degraded scots pine more aggressively, had a more constant growth rate and produced mycelia faster than FPRL280. After sequencing the genome of FPRL280 and comparing it with the published MAD-698 genome we found 660,566 SNPs, resulting in 98.4% genome identity. Specific analysis of the carbohydrate-active enzymes, encoded by the genome (CAZome) identified differences in many families related to plant biomass degradation, including SNPs, indels, gaps or insertions within structural domains. Four genes belonging to the AA3_2 family could not be found in or amplified from FPRL280 gDNA, suggesting the absence of these genes. Differences in other CAZy encoding genes that could potentially affect the lignocellulolytic activity of the strains were also predicted by comparison of genome assemblies (e.g., GH2, GH3, GH5, GH10, GH16, GH78, GT2, GT15, and CBM13). Overall, these mutations help to explain the phenotypic differences observed between both strains as they could interfere with the enzymatic activities, substrate binding ability or protein folding. The investigation of the molecular reasons that make these two strains distinct contributes to the understanding of the development of this important brown rot reference species and will help to put the data obtained from standardized decay tests across the globe into a better biological context