Abstract
Filamentous fungi colonize substrates by forming a mycelium. This network of hyphae can be used as a bio-based material. Here, we assessed the impact of environmental growth conditions and deletion of the hydrophobin gene sc3 on material properties of the mycelium of the mushroom forming fungus Schizophyllum commune. Thermogravimetric analysis showed that Δsc3 mycelium retained more water with increasing temperature when compared to the wild type. The Young’s modulus (E) of the mycelium ranged between 438 and 913 MPa when the wild type strain was grown in the dark or in the light at low or high CO2 levels. This was accompanied by a maximum tensile strength (σ) of 5.1–9.6 MPa. In contrast, E and σ of the Δsc3 strain were 3–4- fold higher with values of 1237–2727 MPa and 15.6–40.4 MPa, respectively. These values correlated with mycelium density, while no differences in chemical composition of the mycelia were observed as shown by ATR-FTIR. Together, genetic modification and environmental growth conditions impact mechanical properties of the mycelium by affecting the density of the mycelium. As a result, mechanical properties of wild type mycelium were similar to those of natural materials, while those of Δsc3 were more similar to thermoplastics.
Highlights
The use of bio-based materials is part of the conversion to a circular economy
A (1,3)-α-linked glucan is located beneath the mucilage, while the inner layer of the cell wall consists of chitin cross-linked to a highly branched (1,3)(1,6)-β-glucan[9,10]
Density of wild type mycelium grown at low CO2 in the dark or at high CO2 in the light was similar (819–1026 kg m−3; Fig. 1, Table 1)
Summary
The use of bio-based materials is part of the conversion to a circular economy. These materials are derived from molecules or structures of microbes, plants, macro-algae, and animals. The outer layer of the S. commune cell wall consists of a water-soluble mucilage of (1,3)(1,6)-β-glucan[9]. This so called schizophyllan is secreted into the culture medium. We assessed properties of wild type and Δsc[3] mycelium of S. commune grown in the light or in the dark at 400 or 70,000 ppm CO2. Mycelium of strain Δsc[3] retained more water with increasing temperature when compared to that of the wild type. Both the absence of SC3 and environmental conditions affected mechanical properties of the mycelium, which can be explained by changes in the density in the mycelium. Genetic modification and environmental growth conditions can be used to create a palette of mycelium materials
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