Researchers have developed a novel biodegradable coating by cultivating an edible fungus on a base of wood fibers, creating a barrier that renders materials like paper and textiles impervious to liquids. This innovation, detailed in the journal Langmuir, presents a promising, food-safe alternative to the single-use plastics found in products like disposable cups and food packaging. The composite film effectively repels water, oil, and grease, addressing a significant source of global plastic pollution with a solution grown from natural components.
The new method harnesses the inherent properties of fungal mycelium—the dense, fibrous root network of fungi—and combines it with microscopic cellulose fibers to create a robust, liquid-proof layer. A team at the University of Maine led the proof-of-concept study, which demonstrated that this bio-based film could be successfully grown on diverse surfaces including paper, denim, polyester, and wood. This breakthrough could pave the way for sustainable materials in both the packaging and textile industries, significantly reducing reliance on petroleum-based plastics that accumulate in landfills and oceans. The lead researcher, Caitlin Howell, emphasized the potential of turning to nature for elegant solutions to pressing environmental challenges.
An Overview of the Innovative Coating
The foundation of this technology lies in a symbiotic combination of two natural materials: an edible fungus and microscopic plant fibers. The fungus, Trametes versicolor, is commonly known as “turkey tail” for its colorful, fan-like appearance. While the mushroom cap is the most visible part of a fungus, the true workhorse is the mycelium, a vast, underground network of fine, thread-like filaments. Mycelium networks are naturally hydrophobic, meaning they repel water, a characteristic that researchers have begun to exploit for creating novel materials like leather alternatives and specialized textiles.
To augment the natural water resistance of the fungus, the researchers integrated cellulose nanofibrils into the formula. These are extremely small fibers derived from wood pulp, the same raw material used to make paper. On their own, cellulose nanofibrils are known for creating dense films that can act as effective barriers against oxygen, oil, and grease. By blending the fungal mycelium with these wood-derived fibrils in a nutrient-rich solution, the team created a composite material that leverages the distinct advantages of both components. The mycelium provides the primary water-repellent chemistry, while the cellulose fibers add mechanical strength and enhance the barrier against other liquids.
The Science Behind the Barrier
The effectiveness of the coating stems from the intricate structure that forms as the fungus grows. When the mycelium and cellulose nanofibril mixture is applied to a surface, the fungus begins to expand, weaving its feathery filaments into and around the cellulose fibers. This process creates a dense, interconnected mat that physically blocks liquids from passing through. The inherent water-repelling properties of the mycelial surfaces ensure that water droplets do not spread out or soak in, but instead remain as tight, bead-like spheres on the surface.
This combined physical and chemical barrier is remarkably effective against a wide range of substances. Beyond water, the coating was shown to prevent the absorption of several other liquids, including organic solvents like n-heptane and toluene, as well as castor oil. This demonstrates its potential to serve as a versatile barrier for various types of packaging, from coffee cups that must hold hot water to food wrappers that need to resist grease and oils. The resulting film is remarkably thin, comparable in thickness to a single coat of paint, yet it provides comprehensive protection without relying on synthetic polymers.
The Application and Growth Process
Creating the fungal coating is a multi-day process that relies on controlled biological growth. First, researchers prepare a liquid suspension containing the T. versicolor mycelia, cellulose nanofibrils, and essential nutrients to encourage growth. Thin layers of this mixture are then applied to the target materials, such as sheets of paper, pieces of denim fabric, or wood veneers.
Incubation and Formation
Once coated, the materials are placed in a warm, controlled environment to allow the fungus to grow. The mycelium network steadily develops over several days, consuming the nutrients and integrating with the cellulose fibrils to form the protective film. The research team found that a minimum of three days of incubation was necessary to develop an effective water barrier. By the fourth day, the coating is well-formed and provides robust protection. This growth phase results in a visible change to the material’s surface, which takes on mottled, organic coloring in shades of yellow, tan, or orange.
Finalizing the Material
After the desired amount of fungal growth is achieved, the materials undergo a final treatment to prepare them for use. The samples are placed in an oven for a full day, a step that serves two critical purposes. First, the heat inactivates the fungus, ensuring that it does not continue to grow or spread. Second, it thoroughly dries the coating, setting the interwoven mycelium and cellulose structure into a stable, durable film. This final step completes the transformation, leaving the base material permanently enhanced with a liquid-proof, food-safe, and fully biodegradable layer.
Performance and Real-World Potential
The proof-of-concept study yielded impressive results across all tested materials. On untreated surfaces, liquids like water would quickly flatten out and soak in completely. In stark contrast, droplets placed on the fungus-treated paper and textiles beaded up into distinct spheres, demonstrating the coating’s high level of repellency. This performance suggests the technology is a viable contender to replace the plastic coatings currently used in countless single-use products. As corresponding author Caitlin Howell stated, “Our hope is that by providing more ways to potentially reduce our reliance on single-use plastics, we can help lessen the waste that ends up in landfills and the ocean.”
Implications for Sustainability
This fungal coating technology arrives at a critical moment, as global efforts intensify to combat the environmental damage caused by plastic pollution. Conventional plastic linings in paper cups, food containers, and wrappers are difficult to recycle and persist in the environment for centuries. By offering a solution grown from edible, biodegradable materials, this research presents a pathway toward a circular economy where products can be safely returned to the earth. Although the technology is still in its early stages, its core components—fungal spores and cellulose fibers—are abundant and readily accessible. Future research will likely focus on scaling up production, optimizing the growth conditions for industrial applications, and testing the long-term durability of the coatings in real-world scenarios.
