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Mycelium is crucial in decomposing biomass and cycling nutrients in nature. While various environmental factors can influence mycelium growth, the role of substrate mechanics is not yet clear. In this study, we investigate the effect of substrate stiffness on mycelium growth. We prepared agar substrates of different concentrations to grow the mycelium, but kept other environmental and chemical conditions consistent. We made a time-lapse recording of the growing history with minimum interruption. We repeated our tests for different species. Our results generally support that mycelium grows faster on a stiffer substrate,Ganoderma lucidumgives the highest growth rate andPleurotus eryngiiis most sensitive to substrate stiffness. We combined experimental characterization and computational simulation to investigate the mechanism and discovered that mycelium concentrates on the surface of a rigid substrate, but penetrates the soft one. Our Monte Carlo simulations illustrate that such a penetration allows mycelium to grow in the three-dimensional space, but effectively slows down the surface occupation speed. Our study provides insights into fungal growth and reveals that the mycelium growth rate can be tuned through substrate stiffness, thus reducing the time for producing mycelium-based composites.

We used agar substrates and tuned its stiffness to culture mycelium and compared tune its stiffness to culture mycelium and compare its growth in a well-controlled condition. Our results revealed that mycelium grows faster on stiffer substrates, thus fully occupying the petri dish surface more quickly. We repeated our study several times by testing four species,P. eryngii,G. lucidum,Trametes versicolor,and Flammulina velutipes,and the stiffest substrate always gives the highest mean growing rate than others. TheG. lucidumshows the highest spreading rate that is obtained on the stiffest substrate as 39.1 ± 2.0 mm²/h. We found that the mycelium on a soft substrate will grow into the substrate instead of spreading on the stiffer surface. Our Monte Carlo simulations further show that once the fibers grow into a three-dimensional substrate, its growth is slower than growing on a two-dimensional surface, providing a microscopic mechanism of the substrate stiffness effect. This study’s analysis of how substrate stiffness impacts mycelium growth is new, bridging a critical knowledge gap in understanding the relationship between substrate mechanics and fungal ecology. The knowledge from this study has a potential in accelerating sustainable manufacturing of mycelium-based composite by adjusting substrate mechanics.

Polyvinyl alcohol (PVA) is a water-soluble synthetic polymer that can be used to make hydrogels for biomedical applications as well as biodegradable bags and films; however, compared to other plastics currently used for containers, it lacks mechanical strength, thermal stability, and can easily absorb water from humid environments. Although mechanical improvement has been observed by blending PVA with collagen in a hybrid hydrogel, there is a lack of fundamental understanding of the molecular mechanism, and it is not clear whether the improvement is limited to a hydrated state. Here, using classical molecular dynamics simulations based on fully atomistic models, we develop the equilibrated molecular structure of PVA with collagen and characterize its mechanics. We show that by interacting with a collagen molecule, PVA is equilibrated to a more ordered structure with each residue interacting with the near neighbors by forming more hydrogen bonds locally, making the structure stiffer than pure PVA. The structure shows higher thermal stability before melting, as well as higher rigidity in water. Our results provide the mechanism of the mechanical advantages of hybrid PVA-collagen polymer. The study demonstrates that the structure and mechanics of a synthetic polymer can be tuned by a tiny amount of a natural polymer at the molecular interface. Moreover, it may shed light on identifying a way to improve the mechanics of biodegradable polymer materials without adding much cost, which is crucial for environmental safety.

Blending natural and synthetic polymers (e.g., polyvinyl alcohol [PVA] and collagen in a hybrid hydrogel) has shown advantages in polymer mechanics, but there is a lack of fundamental understanding. Using molecular dynamics (MD) simulations based on fully atomistic models, we develop the equilibrated structure of the PVA with collagen and characterize its mechanics. We show that by interacting with a collagen molecule, PVA is equilibrated to a more ordered structure with each residue interacting with the near neighbors by forming more H-bonds locally and the structure is stiffer than pure PVA. Moreover, the structure shows a higher thermal stability before the melting point of PVA, as well as higher rigidity in water. Our results demonstrate that the structure and mechanics of a synthetic polymer can be tuned by a tiny amount of a natural polymer at the molecular interface. It provides the mechanism of the mechanical advantages as experimentally observed. This study paves the way for the multiscale modeling and mechanical design of the hybrid polymer material. It sheds light on identifying a way to improve the mechanics of biodegradable materials without adding much cost for both material functionality and environmental safety.