Mycelia inactivation processes – maintaining the flexibility and strength of mycelium-based biocomposites

The current trend towards a sustainable and circular economy proposes the development and use of bio-based materials from renewable resources. Mycelium-based biocomposites (MBB), which consists of defragmented lignocellulosic particles linked by dense mycelium, are an ecological and innovative solution to replace petroleum-based products. MBB have shown advantageous properties, such as acoustic insulation, fire resistance, and the absence of harmful synthetic chemical components. These properties are the basis for the production and use of MBB for a wide range of applications, including paper, textiles, foams for packaging material, vehicle parts, and electronic equipment packaging materials. Briefly, MBB production is achieved through the sterilization the biomass, inoculation and incubation with selected fungi, homogenization, and interruption of fungal growth (or inactivation). Most MBB go through a heating treatment to inactivate the mycelia. However, that treatment results in rigid biocomposites with low flexibility. This work investigated the performance of alternative inactivation methods aiming to achieve flexible but sturdy MBB. Low temperature treatments and CuSO4 were tested in biocomposites obtained from two fungi strains. The inactivation efficiency was evaluated through a cell viability assay, MTT assay. The physical properties of the resulting biocomposites were also assessed. Spraying MBB with a CuSO4 solution did not efficiently inactivate the fungi. Although the low temperatures seemed to have inactivated the fungi two days after treatment (ca. 1% cell viability), 15 days later the mycelia resumed growth again (34% cell viability). Therefore, those treatments did not efficiently inactivate the fungi but left them in a latent dormancy state. None of the tested methods compromised the biocomposites’ flexibility features. Further studies need to be conducted to identify inactivation methods that allow the production of MBB with a more diverse range of physical characteristics to expand their application potential.