Structural, Mechanical, and Genetic Insights into Heat-Pressed Fomes Fomentarius Mycelium from Solid-State and Liquid Cultivations

Abstract

Fungal mycelium-based materials are highly valued for their versatility and for harnessing renewable plant biomass through sustainable biotechnological production. Heat pressing is often used to produce fungal particle boards and leather substitutes. In this study, the impact of heat pressing on fungal mycelium from the basidiomycete Fomes fomentarius under lignocellulose-based solid-state and glucose-based liquid cultivation conditions is investigated, focusing on the changes in cell wall gene expression, morphology, chemical composition, hydrophobicity, and mechanical characteristics. With varying effects between two cultivations, heat pressing at 100 MPa changes hydrophobicity, increases tensile strength and stiffness, in line with hyphal compaction and bonding. Compared to mycelium grown on glucose-based medium, lignocellulosic substrate leads to mycelium with higher β-glucan content, less densely packed mycelium structure and thus lower mechanical strength, probably due to the different expression of genes involved in glucan and chitin biosynthesis. This study highlights the impact of heat pressing on fungal mycelium obtained from different cultivation conditions, offering insights to tailor their performance.