Engineered Biohybrid Mycelia Materials with Hierarchical Structure Control

Mycelia materials are composed of filamentous fungi, in which hyphal extensions grow into randomly oriented crosslinked networks. Engineered living materials (ELMs), including those generated from mycelia, demonstrate comparatively lower strength and toughness. Here, we leverage processes used by nature such as alignment and biomineralization to form complex hierarchical structures to achieve increased strength. We investigate mycelia materials composed of the fungus, Aspergillus niger, in fiber and film geometries. The A. niger cells are engineered to express silicatein on the cell surface, which acts as a template for silica mineralization. After fiber incubation, printed fungal cells display radial hyphal growth, extending from the core fiber, that can be tuned by capillary force alignment. The radial density of hyphae depends on oxygen and nutrient availability. Mineralized mycelia, in both geometries, demonstrate statistically significant increases in elastic modulus and maximum stress compared to non-mineralized, which we associate to the silica deposition from enzymatic activity of silicatein-alpha in catalyzing the mineralization. Further, twisted and braided fibers demonstrate an increase in fracture strain compared to single fibers, suggesting a toughening mechanism indicated by multi-stage fracture in stress-strain curves. Overall, our results provide insights into how biomineralization and hyphal alignment impact the mechanical properties of mycelia materials.