Uncovering the Design Rules for Sustainable Growth of Mineralized Mycomaterials

Mycomaterials, materials made from filamentous fungi, have several advantages over traditional materials, such as their genetic programmability and self-healing properties. However, their lack of mechanical strength and cost of production often constrain the applications they can be used in. In this work, we take inspiration from natural systems to overcome these challenges by elucidating design principles for mineralization-based enhancement of mechanical strength and synthetic lichen-based low-cost growth. We demonstrate that surface display of an enzyme from sea sponges, silicatein α, on the hyphae of the filamentous fungus Aspergillus niger enables mineralization of polysilicate and that this does not impact fungal growth. We also show that this strategy can be extended to other silicatein α variants and characterize how the degree of mineralization can be modulated. We then demonstrate that mineralization enhances the mechanical properties of the mycelium, including its tensile strength, modulus, and toughness. Finally, we show how these reinforced mycelia can be grown without external carbon sources using a synthetic lichen-based co-culture to facilitate low cost biomanufacturing. Together, our results lay the groundwork for the sustainable production of mineralized mycomaterials and create a new model system to study how mineralization impacts growth and mechanical properties. Significance Statement Materials: made from filamentous fungi, called mycomaterials, have several advantages over traditional materials, but their poor mechanical properties and relatively high production costs have limited their application. We elucidated design principles to enable tunable mineralization of fungal mycelium and have shown that it does not impact growth but significantly enhances mechanical strength. We have also shown that these reinforced mycelia can be grown without any external carbon in a synthetic lichen like consortia to minimize production costs. This work creates a novel experimental system to study how mineralization impacts growth and mechanical properties and will facilitate the broader application of mycomaterials in the future.