Pure mycelium materials from Schizophyllum commune

Mycelium materials, made from fungi like Schizophyllum commune, are emerging bio-based, sustainable alternatives for leather and textiles. Monokaryons, with one nucleus per cell, have so far been used to produce mycelium materials of S. commune. However, mutations in monokaryons can easily affect biomass and material properties. Such phenotypic instability was investigated for the streak mutant that occurs frequently in S. commune. Genomic analysis and complementation revealed that insertion of a transposable element in the Gβ gene causes this mutation. The second nucleus in dikaryotic cells masks recessive mutations, enhancing phenotypic stability. Therefore, material properties of S. commune dikaryons were assessed. Notably, dikaryons outperformed the properties of monokaryons, producing materials up to 10 times stronger and 5 times more ductile. In fact, two dikaryons produced the strongest mycelium materials reported so far. Untreated mycelium materials are brittle, requiring post-treatments to meet textile and leather standards. Treatment with different vegetable and synthetic cross-linkers in combination with glycerol improved tensile strength to leather-like levels. Cross-linking also reduced water absorption, and enhanced resistance to enzymatic degradation. Spectroscopic and amino acid analyses showed that cross-linking targets protein amino groups and polysaccharide hydroxyl groups. Small molecules like glycerol improve ductility but migrate outside the material. Alternatives such as polyglycerol and polyglyceryl fatty acid esters displayed improved ductility with reduced migration up to 11.5-fold, offering better long-term performance. Together, this thesis resulted in new insights to improve mycelium materials, thereby offering the possibility to introduce them as a viable, sustainable alterative for leather and textiles.