Anisotropic Growth of Filamentous Fungi in Wood Hydrogel Composites Increases Mechanical Properties

There is a rising demand for sustainable, biodegradable, and robust materials in response to growing environmental concerns. Here, we propose using delignified wood as a scaffold for fungal proliferation to obtain wood-fungi composites. The delignification process preserves the fiber directionality inherent to natural wood, enabling fungi to grow along these fibers, enhancing the composites' mechanical properties, and promoting anisotropic fungal growth. The delignified wood was used as a scaffold for the growth of <i>Aspergillus oryzae</i> and <i>Rhizopus oligosporus</i>. Both wood-fungi composites exhibited a higher mechanical strength after fungal proliferation. We used balsa, poplar, and spruce as wood to demonstrate the effects of varying wood architectures. Even though the tensile strengths of all three wood scaffolds were not significantly different, wood scaffolds with lower densities promoted fungal growth. Increasing agar and glucose concentrations were found to significantly enhance tensile strength and Young's modulus. The tensile strength and Young's modulus of wood scaffolds increased from 10¹ kPa to nearly 10³ kPa and 10^-3 GPa to nearly 10^-1 GPa, respectively. These results highlight the versatile nature of delignified wood as a platform for fungal growth. It offers tunable properties that can be optimized for various applications in composite manufacturing.