Fungal Strain Influences Thermal Conductivity, Hydrophobicity, Color Homogeneity, and Mold Contamination of Mycelial Composites

Mycomaterials are biomaterials made by inoculating a lignocellulosic substrate with a fungus, where the mycelium acts as a binder and enhances material properties. These materials are well suited as sustainable alternatives to conventional insulation materials thanks to their good insulation properties, low density, degradability, and fire resistance. However, they suffer from mold contamination in moist environments and poor perception ("organic" appearance). Furthermore, most mycomaterials to date have been derived from a limited range of fungal species, leaving the vast phenotypic diversity of fungi largely untapped. We hypothesized that by exploring a broader range of strains, we could enhance the likelihood of discovering a material that meets the needs for insulation panels. We generated mycomaterials from nine fungal strains and measured their thermal conductivity, mold resistance, and perception properties. We observed significant variations across strains on these three parameters. Thermal conductivity ranged from levels comparable to extruded polystyrene to nearly as effective as polyurethane (0.039 to 0.019 W/mK). All materials generated were hydrophobic (equivalent to 105-122° contact angle), but differed by a factor of two in color appearance and sensitivity to mold (0-94% of surface colonized). We also found a method to improve resistance to mold using deactivated contaminant propagules.