Biological attack of acetylated wood [Elektronische Ressource] / vorgelegt von Behbood Mohebby

Behbood Mohebby

Informations

• Publié par: georg-august-universitat_gottingen
• Publié le: 01 janvier 2003
• Nombre de lectures: 26
• Langue: English
• Poids de l'ouvrage: 22 Mo

Extrait

Behbood Mohebby
Ph.D. Thesis

Institute of Wood Biology and Wood Technology
Faculty of Forest Sciences and Forest Ecology
Georg-August-Universität Göttingen
Göttingen 2003















vorgelegt von

Behbood Mohebby

geboren in

Zanjan (Iran)





Ph.D. Thesis

Institute of Wood Biology and Wood Technology

Faculty of Forest Sciences and Forest Ecology
Georg-August-Universität Göttingen









Göttingen 2003 Die Deutsche Bibliothek – CIP – Einheitsaufnahme

Mohebby, Behbood
Biological attack of acetylated wood
vorgelegt von Behbood Mohebby, Göttingen, Cuvillier, 2003
Zugl.: Göttingen, Univ., Diss., 2003
ISBN



D 7

1. Berichterstatter: Prof. Dr. H. Militz
2. Berichterstatter: Prof. Dr. A. Hüttermann
Tag der mündlichen Prüfung: 12.05.03






















To my dears who have spent their life for me:
Lobat, Yashar, Camellia
and great Parents






























Acknowledgements

Who does not thank God’s creatures, does not appreciate him.
(Holy Koran)

Hereby, I would sincerely appreciate my merciful and great God who helped me all time in my life, in
happy and sad moments.
It would truly be expressed the best appreciations to my supervisor Prof. Dr. Holger Militz who has
spent four years of his time with me to conduct this research. Two years of this research has been spent in
The Netherlands, Wageningen University and two years in Germany, Göttingen University with him.
My great thanks and sincere to Dr. Reyes Sierra-Alvarez for co-supervising this research during first
two years of my PhD research in Wageningen University.
In general, all people in Wageningen University should be appreciated for their friendly cooperation in
Sub-department of Forestry, Wood Science Chair, Hans Polman, Johan Velthuizen, Egbert Nab, Kathinca
Huisman, Rut, Joke …
Special thanks to Dr. Kose Kaijzer and Mr. Wim Veenaandaal for their friendly cooperation in electron
and light microscopy in Laboratory of Plant Cell and Biology (PCB), Wageningen University.
Cordial thanks to all people in SHR (Stichting Hout Research Institute, The Netherlands), Dr. Rene
Klassen, Erwin Beckers, Bass Hollebom and others for helping me in acetylation of samples and some
other laboratory works.
My great appreciation should be expressed to my kind and helpful friend Dr. Carsten Mai who co-
supervised me in some parts of this research in Göttingen University. He spent lots of his time in our
scientific and friendly talks and discussions.
I would also express my cordial thanks to Prof. Hütterman, Dr. Anje Marcherjeck and Mr. Mojtaba
Zomorrodi for their very friendly cooperation in bioassay part of this work in Forest Botany Institute,
Göttingen University.
Finally great thanks to Dr. Ulrich Junga, laboratory technicians and all people in Institute of Wood
Biology and Wood Technology for their friendly cooperation during this research.












Abstract
Acetylation is an environmental friendly method to modify wood properties and protect it against
biological attack. Many researches have been done in this field. However, no concern was paid for mode of
protection in acetylated wood. This research had been aimed to study mode of action in acetylated wood by
investigating on weight and MOE loss, chemical alteration in cell wall due to microbial attack, IR-
spectroscopy, microcalorimetry, determination of fungal biomass by using ergosterol assay and FDA
hydrolysis and enzyme assays. Beech and Scots pine wood samples were acetylated by using acetic
anhydride at temperature 80-120°C for 180min. Acetylated wood samples were tested under soil bed test
condition, filed and basidiomycete trials. Results showed that the losses of weight and MOE decreased at
increasing weight gains. Soil bed test revealed that the acetylation of beech wood at above 8% and pine
wood at above 10% inhibits soil microorganisms in attacking wood and their activities reached to nil at
higher weight gains. A test with the white rot fungus (T. versicolor) showed that the weight loss decreased
at raising weight gains. Weight gains of above 10% inhibited fungal decay in beech wood and it reached to
zero at higher weight gains. Microscopical studies of wood from soil bed samples, field trials and
basidiomycete (white- and brown-rot) tests showed that fungi could colonize acetylated and non-acetylated
wood. However, measurements of fungal biomass by using ergosterol assays in those woods and
fluorescein diacetate in white rot tests showed a rapid colonization of fungal hyphae at early stages of
incubation and decreased amount of fungal biomass at raising weight gains. Results showed that fungal
colonization is influenced by the acetylation. Biological activities were measured in wood by using
microcalorimetry. The reduction of thermal powers and measured amounts of energy production in
acetylated wood revealed that activities of microorganisms were influenced by the acetylation and their
activities decreased at increased degree of the acetylation. Microscopy of field trial samples showed that
the acetylation of wood was affected the growth of soil microorganisms and protected wood against soil
microorganisms during a long period of exposure (350 weeks) to soil. Different types of decay in field
samples showed successional activities of soft- and white-rot fungi and also bacteria. Soil bed test showed a
synergism between soil fungi and bacteria in wood. It was revealed that bacteria followed hyphal traces in
cells and associated with fungi in wood degradation. Chemical analyses of acetylated wood in soil bed
samples showed a significant effect of the acetylation on removal of cell wall components. The analyses
showed a reduction in removal of cell wall components at increased weight gains. Results revealed that
removal of the cell wall components reduced considerably in beech wood at weight gains above 8% and in
Scots pine samples at above 10%. Study on patterns and phenology of white- and brown-rot decay on
acetylated wood showed no difference of decay patterns between acetylated and non-acetylated wood,
however decay patterns appear more later in acetylated wood.
Keywords- acetylation, beech, Scots pine, mass and MOE loss, soil bed test, field test, basidiomycete, dyn
soft rot, bacterial degradation, white rot, brown rot, Trametes versicolor, Poria placenta, light microscopy,
SEM, chemical analysis, IR spectroscopy, ergosterol assay, FDA analysis.
Contents
Chapter 1
Research background
1.1. Introduction …………………………………………...... 1
1.2. Chemical wood modification …………………………………………...... 1
1.2.1. Etherification …………………………………………...... 2
1.2.2. Esterfication …………4
1.2.3. Urethanes …………………………………………...... 7
1.2.4. Oxidation …………………………………………...... 8
1.2.5. Silylation
1.3. Acetylation of wood …………………………………………...... 10
1.3.1. Acetylation processes ……………………
1.3.2. Properties of the acetylated wood ………………………………...... 11
1.4. Other types of wood modification ……………………...... 16
1.4.1. Thermal wood modification ………………………………
1.4.2. Enzymatic wood modification ……………………...... 18
1.5. Aims of this thesis ………………………………...... 19
References ……………………...... 19
Chapter 2
Soil bed trials with acetylated wood
Material and methods …………………………………………...... 30
2.1. Sample preparation …………
2.2. Acetylation ………………………………...... 30
2.3. Soil bed trials …………31
2.3.1. Sample preparation …………………………………………......
2.3.2. Determination of dynamic Modulus of Elasticity (MOE )…………...... 31 dyn
2.3.3. Soil bed preparation ………………………………...... 32
2.3.4. Chemical analysis …………33
2.3.4.1. Extractives free wood preparation……………………………………......
2.3.4.2. Klason lignin …………………………………………...... 33
2.3.4.3. Holocellulose …………...... 33
2.3.4.4. α-Cellulose…………………………………………34
2.3.4.5. IR spectroscopy …………......
2.3.5. Microscopy …………………………………………...... 35
2.3.5.1. Light microscopy ……………………
2.3.5.2. Scanning Electron Microscopy………………………………………...... 35
2.3.6. Microcalorimetry …………………………………………...... 35
2.3.7. Ergosterol assay in decayed wood ……………………36
2.4. Results and discussion …………………………………………...... 37
2.4.1. Mass and MOE losses ……………………dyn
2.4.2. Chemical analysis …………………………………………...... 40
2.4.3. Microscopy …………………………………………...... 42
2.4.4. IR spectra of acetylated wood …………………………………………...... 51
2.4.5. Microcalorimetry …………………………………………...... 57
2.4.6. Ergosterol assay…………58
2.5. General conclusion …………………