Microorganisms (fungi, algae, lichens and bacteria) can colonize biofilms, shorten their life span, impair their function and aesthetic appearance and cause hygienic problems. Most fungi are considered to be a public safety hazardalthough the beneficial effects of fungi far outweigh their negative. If they are applied selectively they can optimize material properties. For pure and appliedresearch we use a range of fungal species and enzymes to positively enhance the properties of wood. The application of wood inhabiting fungi results ina significant improvement of the acoustic properties of tonewood. Wood durability of refractory, native tree species such as Norway spruce and Fir is enhancedby the bioincising process which results in a significant increase in wood permeability. Bioincising is a promising technology to enable an efficient distributionof wood modification substances and to promote the efficiency of the desired property improvement.
Mycowood: improved acoustic properties for violins
The quality of wood for the manufacture of music instruments (tone wood) is determined by its physical properties. Wood with a low density and high velocity of sound and modulus of elasticity is favored for string instruments making. The objective of our investigations is to improve the physical quality of tone wood, e.g. reduce the density, and thus increase the sound radiation by exposing it to specific decay fungi under controlled conditions. The latter fungi differ from most other fungi, as they reduce density but do not degrade highly lignified cell wall regions resulting only in negligible changes in the stiffness and velocity of sound which are thought to be important for the sound quality of string instruments.
With the support of the Walter Fischli-Foundation we have developed a procedure which did result in mycowood of optimised quality and physical stability. Violins have been built by two different makers using the incubated mycowood and its non-incubated controls. Studies are being designed which will show the differences of these violins in sound characteristics and acoustic properties at Empa, and their psycho-acoustic differences by CD recordings at the sound design studio "Idee und Klang" in Basel. A first mycowood violin, a copy of the "Caspar Hauser" violin by Guarneri del Gesú, was recorded with a movement of the violin concerto by Ludwig van Beethoven with soloist Oleg Kaskiv and the Gstaad Festival Orchestra, and demonstrates its fine and differentiated sound.
Microstructure-property relationship in varnished wood of string instruments
Wood varnish coatings are not only aesthetically important, but also preserve the musical instrument from wear and fluctuations in the ambient humidity. Depending on the thickness, extent of penetration into the wood and the physical and mechanical properties after hardening, varnishes may change the mechanical and also vibro-acoustical properties of the coated wood. Although some recent studies suggest that solists cannot distinguish between high quality contemporary violins and historical ones still the soloists and collectors believe in the superior quality of sound of the former violins manufactured by Cremonese masters, and the quality of their timber and varnish. Our ultimate goal is to contribute to the scientific understanding of the role of the varnish composition and its structure at the wood-varnish interface on the vibro-acoustics of string instruments. This knowledge helps to develop a generation of high quality varnishes for string instruments.
Enhanced permeability of spruce by fungi modification
Aspiration of bordered pits in Norway spruce wood is the main reason why the treatibility with preservatives is greatly inhibited for increasing the durability against micro-organisms. If this restriction could be overcome wood could be treated more effectively. For this purpose Norway spruce wood is exposed to the white-rot fungus Physisporinus vitreus that selectively degrades the pit membranes, without altering the mechanical properties of wood. At present we are undertaking studies to optimize conditions under which the colonization of wood by the fungus is improved with the objective to upscale our patented procedure as a biotechnological method for industrial purposes.
Laccase-catalysed iodination of wood for achieving antimicrobial effects and protection against microbial degradation
Current methods of functionalization of wood and wood-based materials for antifungal and antibacterial effects rely mainly on the adsorption of bioactive (toxic) compounds. Exposure to physical and chemical forces of the environment, particularly to water, mostly leads to rapid loss of efficacy of antimicrobial surfaces due to leaching. Our studies show that laccase-catalysed oxidation of iodide can be used for generating leaching resistant antimicrobial wood surfaces which effectively prevent colonization against different classes of heterotrophic microorganisms, including enteric bacteria, yeast, bluestain and wood decay fungi.
Development of a biological control method to eradicate the inoculum of copper tolerant fungi in the soil of wood products using antagonists
Wood poles impregnated with copper based wood preservatives are popular and used in the telecommunication and power supply industries all over the world because of their high strength per unit weight, low installation and maintenance costs and excellent durability. Premature failure of wood poles is often the result of wood decay caused by copper tolerant fungi. The objective of this project is to develop a biological control method that can be applied for eradicating copper tolerant fungi of the genus Poria in the soil surrounding wood products. For the purpose we will isolate a range of antagonists from soils on different sites in Europe in which early failure of wood poles are commonly encountered. Once we have isolated and identified the copper tolerant fungi we will complete a range of in intra and in vivo studies that we will enable identification of an antagonist. If this approach is successful it should be possible to drastically reduce the number of early failures of wood poles and other wood products in Europe.
Figure above: Early failure of a wood pole, which was impregnated with a chromium copper formulation. The copper tolerant fungus Poria placenta = Rhodonia placenta was isolated from the decayed wood. Pic.A: Dense, with mycelium has colonized the wood of an incubated control specimens. Pic.B: After pre-treatment with the antagonist T-Cu+ wood specimens were not colonized by Rhodonia placenta.
Superior tonewood has a low density and high Young‘s modulus of elasticity. The acoustic properties of Norway spruce and Sycamore wood can be improved with a controlled degradation process.
Wood of Norway spruce and white Fir is weakly durable, has a low liquid permeability and can be only poorly treated with selected wood modification substances.
Wood decay fungi secrete enzymes which specifically attack the wood polymers. Lignin-degrading enzymes such as laccases can be used for green chemistry, or the production of wood compound materials.
Competences / methods
- Determination of the cause for microbial decomposition of wood plastics, metals, organic and an organic materials
- Research on the selective modification of wood with fungal species and fungal-derived enzymes
- Elucidation of the durability of wood against microorganisms under different environmental conditions
- Determination of the efficiency of wood preservatives and wood modification methods against microbial colonization and decomposition.