Xyhlo Biofinish is a natural and environmentally friendly wood protection concept based on linseed oil impregnation and a fungal-based coating. It emerged in the late 1990s and has been developed over the past 15 years into an industrially applicable process in the Netherlands. The combination of linseed oil impregnation and a surface treatment with the living fungus Aureobasidium extends the service life of wood outdoors and significantly reduces maintenance costs. Aureobasidium grows on water-repellent linseed oil surfaces in many regions of the world which enables the use of this concept in a wide range of applications. Tests demonstrate that its reproducible stable outdoor performance allows it to withstand the environmental conditions in at least the northern hemisphere. Linseed oil apparently stimulates growth of Aureobasidium on surfaces and it can function as repellent for liquid water into the wood. However, water vapour is still able to diffuse in the wood which creates a diffusion-open system that swells and shrinks slower. Research on the biofinish concept is still ongoing and more information about the mode of adhesion of the fungus to the wood surface is necessary. The aim of this study was to gain more information about the mode of adhesion of the fungus Aureobasidium to the wood surface and to investigate its relation to the fungal morphology. Aureobasidium produces extracellular polymeric substances (EPS) which enable the attachment of cells to surfaces and biofilm formation. EPS consist among other biopolymers of the polysaccharide pullulan, which is known for its mediation in adhesion and attachment. In this study, EPS was extracted from the fermentation suspension of several morphologically different Aureobasidium cultures and examined on their shear strength. Results showed that the EPS collected from shiny (more light reflecting) black cultures of Aureobasidium performed better in shear tests compared to EPS from matt black cultures and matt light grey/white fungal cultures. This suggests that the morphological appearance of Aureobasidium cultures correlates with the adhesion to surfaces.

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