Wood, often referred to as the “building material of the 21st century”, has gained recognition as an attractive alternative to several traditional building solutions. To enlarge the application of wood, several properties including biotic and abiotic degradation resistance need to be improved. Consequently, new solutions are available on the market that ensure expected properties and functionality over extended service life and reduce the risk of product failure. The latest trends are driven by biomimicry, an approach that captures and exploits properties that have evolved in nature. This was a strong motivation for the development of an alternative nature-inspired coating system using the yeast-like fungus Aureobasidium pullulans as a living component. A. pullulans is widely found in nature and has unique properties, such as forming biofilms or digesting various nutrients. The majority of research on biofilms focuses on preventing its formation while leaving their protective applications unexplored. Understanding the mechanisms of fungal growth, their ability to utilise different nutrients and form biofilms, are necessary to develop a technically applicable, controlled, and optimised biofilm that effectively protects the substrate surfaces. This study investigated the growth and biofilm formation of A. pullulans on different lignin derivatives, namely, vanillin, phenol, 4-hydroxybenzoic acid, and p-coumaric acid. The ability of the fungi to utilise lignin derivatives in poor, synthetic nutrient media and rich malt extract media was determined, and the amount of biofilm produced was quantified. Fungal growth was visualised using a transmitted light imaging system (EVOS M7000, ThermoFisher Scientific), which captured projection images at defined time intervals. The acquired images were used for evaluating the morphological characteristics of the developing fungal biofilm. Furthermore, they served as quantitative data for the analysis of various morphological and growth parameters of A. pullulans. The combination of time-lapse microscopic observation, with mathematical analysis, offers valuable insights into the first steps of fungal growth that are crucial for our understanding of biofilm development. This knowledge can be used for developing alternative living protective biofilms as well for understanding bioreceptivity of materials and growth mode of early fungal colonisers.

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