Ehsan Bari

Mechanical properties and chemical composition of beech wood exposed for 30 and 120 days to white-rot fungi

Abstract The effects of exposing specimens of Oriental beech [Fagus sylvatica subsp. orientalis (Lipsky) Greuter and Burdet] to the white-rot fungi Pleurotus ostreatus (Jacq.: Fr.) Kummer and Trametes versicolor (L.: Fr.) Pilát strain 325 have been studied concerning the mechanical properties and chemical composition in terms of carbohydrates, cellulose, and lignin. Biological decay tests were carried out in accordance with the EN 113 standard specifications for 30 and 120 days. P. ostreatus had nearly the same deteriorating effects on the mechanical properties and chemical composition as that caused by T. versicolor. High and significant correlations were found between some mechanical properties with chemical components; for instance, the correlation coefficient (R2) between impact bending and carbohydrate content was about 0.96. The changes of components influence the various mechanical properties to a different degree. Incipient fungal decay caused severe changes for impact bending and carbohydrate loss. Several other properties declined at 120-day exposure time, such as the hardness, compression strength parallel to grain, and cellulose and lignin losses.

EFFECTS OF NANO-CLAY ON BIOLOGICAL RESISTANCE OF WOOD- PLASTIC COMPOSITE AGAINST FIVE WOOD-DETERIORATING FUNGI

Effects of nano-clay on weight loss of wood-plastic composites (WPC) by five fungi were studied. Nanoclay particles of 20 to 50 nm size were applied at 2, 4, and 6% WPC of 0,90 g/cm3 density. The white-rot fungi Physisporinus vitreus, Pleurotus ostreatus and Trametes versicolor as well as the brown-rot species Antrodia vaillantii and Coniophora puteana were used. Mass loss tests were conducted according to the European standard. The highest (3.2%) and lowest (0,2%) mass losses were produced by T. versicolor and P. vitreus in the control and 6%-nanoclay treatments, respectively. Obviously the weight loss of WPC depends on the fungus species. Although weight losses were extremely low, nano-clay considerably inhibited the growth of wood-deteriorating fungi. Mass loss correlated with water absorption.

Natural decomposition of hornbeam wood decayed by the white rot fungus Trametes versicolor

The impacts of white-rot fungi on altering wood chemistry have been studied mostly in vitro. However, in vivo approaches may enable better assessment of the nature of interactions between saprotrophic fungi and host tree in nature. Hence, decayed and sound wood samples were collected from a naturally infected tree (Carpinus betulus L.). Fruiting bodies of the white rot fungus Trametes versicolor grown on the same tree were identified using rDNA ITS sequencing. Chemical compositions (cellulose and lignin) of both sound and infected wood were studied. FT-IR spectroscopy was used to collect spectra of decayed and un-decayed wood samples. The results of chemical compositions indicated that T. versicolor reduced cellulose and lignin in similar quantities. Fungal activities in decayed wood causes serious decline in pH content. The amount of alcohol-benzene soluble extractives was severely decreased, while a remarkable increase was found in 1% sodium hydroxide soluble and hot water extractive contents in the decayed wood samples, respectively. FT-IR analyses demonstrated that T. versicolor causes simultaneous white rot in the hornbeam tree in vivo which is in line with in vitro experiments.

Monitoring the cell wall characteristics of degraded beech wood by white-rot fungi: Anatomical, chemical, and photochemical study

Meticulous chemical analysis of decaying xylem and linking it to corresponding anatomical modification at the cellular level can improve our understanding of the decay process. The aim of this study was to monitor the histological, chemical, photochemical, and progression of wood degradation by two white-rot fungi at different intervals. Oriental beech wood (Fagus orientalis) blocks were exposed to Pleurotus ostreatus and Trametes versicolor to investigate the degradation capabilities of these two fungi. Light microscopy was used to study the decay patterns in wood. Decayed wood samples were also analyzed to determine lignin, cellulose and sugar contents and also evaluated at two week intervals by FT-IR spectroscopy to study chemical alterations. According to chemical analyses lignin is the most degraded polymer followed by cellulose and hemicelluloses for both white rot fungi. However, both test fungi tended to consume lignin more than cellulose. FT-IR spectra changes for lignin and carbohydrates in beech wood supported chemical alteration and indicated that both fungi decay wood in a simultaneous pattern.

How nano-wollastonite can change the fundamental properties of a wood fibre and rice straw composites?

The potential of using rice straw (RS) in combination with wood fibre in the production of medium density fibreboard was investigated. Nano-wollastonite (NW) was added to some of the panels to determine if it would enhance the physical and mechanical properties. It was found that satisfactory composite boards could be made with the addition of 10% RS to the wood fibre. Furthermore, the mechanical and physical properties of the composite were enhanced when NW was added.

Assessing the Biodiversity of Wood Decay Fungi in Northern Forests of Iran

Fungal diversity in the Hyrcanian forests can greatly vary due to diverse ecological conditions. The scope of the present research was to investigate the diversity of wood decay fungi at three sites in the northern forests of Iran. Fruiting bodies of fungi were collected in three plots dominated by Quercus castaneifolia C.A.M. (oak) and Carpinus betulus L. (hornbeam) in the Hyrcanian Forest. As many as 19 and 13 taxa were found on hornbeam and oak, respectively. The identification of these fungi revealed Fomes fomentarius (L.) Fr. and Ganoderma lucidum (Curtis) P. Karst. as highly abundant on hornbeam and oak, respectively. Highest fungal abundance was observed at an altitude range of 1150-1200 meters above sea level. Diversity of macro-fungi was determined and the mean Shannon diversity index was found to be 2.52 and 1.94 for hornbeam and oak, respectively, and mean equitability was calculated as 0.84 and 0.73 for hornbeam and oak, respectively. There were no significant differences in the Shannon Diversity Index or equitability. Overall, current work showed that most of the identified fungi were classified as white rot fungi.