Deletion of sc3 , Alone or in Combination with sc15 , Alters Mycelial Surface Wettability and Substrate-Dependent Adhesion in Schizophyllum commune

Abstract Fungal mycelium has attracted increasing interest as a sustainable alternative to petroleum-derived adhesives and functional coatings. However, the interfacial mechanisms that govern fungal adhesion and surface interactions are still not fully understood. In this study, we investigated how deletion of the hydrophobin gene sc3 either alone or together with the hydrophobin-like sc15 gene impacts extracellular polysaccharide secretion, mycelial surface properties, and adhesion in the basidiomycete Schizophyllum commune. Two wild-type strains (H4–8A and 4–39) and the Δsc3 and Δsc3Δsc15 strains were grown in liquid shaken conditions and under static conditions on glass, Teflon, and wood that had been placed on agar medium. Production of the extracellular polysaccharide schizophyllan was increased in the Δsc3 and the Δsc3Δsc15 strains when compared to the wild-type strain. Moreover, unlike the wild-type strains, the deletion strains produced a hydrophilic instead of a hydrophobic mycelium at the air-exposed side, which was accompanied by reduced aerial hyphae formation. While all strains adhered strongly to wood, wild-type strains attached more strongly to hydrophobic Teflon than the Δsc3 and the Δsc3Δsc15 strains. Adhesive bonding strengths on birch wood veneer ranged from 1.31 to 1.83 MPa, with the Δsc3Δsc15 mutant showing the highest strength after growth on this substrate under static conditions and Δsc3 after growth in liquid shaken cultures. These results demonstrate that deletion of sc3, either or not in combination with sc15 impacts substrate-specific adhesion, while increased formation of schizophyllan in these strains did not consistently correspond to increased bonding.