By 2050, global roundwood processing is projected to generate over 329 mtons of side-streams per year, including wood chips, particles and residues, with 42 mtons originating from Europe [1] . Due to their molecular complexity, these side streams are highly recalcitrant and are primarily utilised for energy production. However, there is a growing interest in repurposing these residues within second-generation biorefineries to produce a wide range of high-value products and materials. 
This study explores the potential of fungal biotechnology to valorise spruce wood chips. Through solid-state fermentation (SSF), certain fungal species can efficiently colonize and degrade woody biomass by secreting a diverse array of lignocellulolytic enzymes. These extracellular enzymes can be recovered as an enzyme cocktail with broad applications in biorefineries. A literature review identified Pleurotus ostreatus, Ganoderma lucidum, and Fomes fomentarius as promising candidates for this process. 
Understanding the innate wood degradation approach of those fungi is crucial for optimizing their use in biorefineries. Building on the selection of the mentioned species, this research work begins with a detailed characterisation of spruce biomass. Spruce wood cell walls consist of microfibrils: crystalline cellulose chains (~40%DW) sheathed in a crosslinked lignin-carbohydrate complex (LCC) of hemicellulose (~28%DW) and lignin (~30%DW), with the remainder consisting of extractives and ash. The impact of fungal colonisation of the wood is then monitored over time through substrate and secretome analyses. Changes in the lignocellulose are assessed though ionic chromatography (HPAEC), lignin quantification, and bond analysis via Fourier transform infrared spectroscopy (FTIR). Additionally, enzymatic activity in the fungal secretome is analysed to elucidate degradation strategies and identify key enzyme combinations responsible for LCC breakdown. These insights will help refine fungal biotechnology approaches for efficient biomass valorisation in biorefinery applications.