FAIR-CT97-3689 Sustainable wood / new clean technology methods for the control of fungal stains in wood

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Biotechnology : FAIR Area 1.3 - Forestry-Wood Chain : Integrated Crop Protection & Biological Control : Solid Wood Products : Wood (Lignocellulose)

	Contract No:	FAIR-CT97-3689
	Date Prepared:	September 2000
	Source:	Second Annual Progress Report Abstract and Executive Summary

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Second Annual Progress Report Executive Summary

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Second Annual Progress Report Abstract

The overall objective of the project is to find potential biocatalysts and/or environmentally sustainable chemicals for the prevention and decolouration of wood damaging stains, caused by bluestain and mould fungi, and to develop new methods based on these biological compounds as alternatives to conventional biocides.

During the second research year, the study of biochemical and genetic factors affecting the fungal pigmentation has continued. The characterisation of the modes of action of selected antagonists and the isolation and characterisation of decolouring enzymes produced by selected melanin decolouring fungi has been carried out. The application methods based of biological agents have been studied in laboratory scale. Selected biological agents (enzymes and biocontrol strains) have been produced for laboratory and field scale evaluation of prevention and decolouring potential, ecotoxicity testing and field tests. The laboratory and field tests and evaluation of ecotoxicity of the most promising methods have been started.

The formulation, laboratory evaluation and ecotoxicity testing of the chemical prevention and decolouring products has been continued. The evaluation of efficacy of the chemical products in out-door exposition tests is ongoing.

Several promising new chemical and biological agents for the prevention of fungal stains have been identified. Evaluation of the efficacy and environmental impacts of the new methods under laboratory and field test conditions is underway. The investigation of the melanin biosynthesis pathways in selected bluestain fungi by using inhibitors of DHN pathway indicates that DHN pathway is functioning in the fungal isolates studied. Two genes involved in DHN melanin biosynthesis were cloned and characterised from the bluestain fungus Ophiostoma floccosum.

Two fungal isolates were shown to effectively decolourise melanin on nitrogen limited growth conditions. Melanin decolouring enzymes of the selected fungi have been isolated and identified. Melanin decolourisation was obtained by using laccases and peroxidases. The decolouring activity of laccases was enhanced by low molecular weight mediators. The results of the laboratory scale tests on stained wood indicate that the bleaching effects obtained in liquid tests using isolated melanin are not easily reproduced on solid wood. The work is continued to develop enzymatic bleaching methods effective on solid wood.

Work to identify the mode of action of biocontrol bacterial and yeast isolates has indicated that competition for lipid nutrients in wood is unlikely to be an important mechanism of action. The yeast Debaryomyces hansenii produces extracellular anti-fungal compounds which effectively reduce fungal growth, whereas bacterial isolates produce volatile compounds capable of reducing growth and pigment production by staining fungi.

Wood block tests using the bacterium Serratia liquifaciens and the yeast D. hansenii have indicated that a cell density of approx. 10⁹ cells/cm² provides a considerable reduction in staining. The cells of the yeast have been shown to reproduce and survive on wood surfaces. The evaluation of the efficacy of the biocontrol organisms S. liquifaciens and D. hansenii in wood block tests in the laboratory under controlled environmental conditions and in field tests is still in progress.

New chemical treatments to prevent the growth of sapstain fungi on wood have been formulated. Based on preliminary results of the out-door exposition tests, several of the new formulations show good efficacy against fungal growth and stain. Based on the results of ecotoxicology testing, two formulations showing the best environmental profile are proposed for further studies.

During the next reporting period results on the prevention potential and environmental impacts of selected biological and chemical agents will be obtained from laboratory and field scale tests. The most promising methods will be tested in field tests on large dimension lumber. Industrial survey and market study of the novel clean technology methods and their end-use possibilities will be carried out