Currently, there are several plant-based leathers commercially available, but many of them include a small amount of polyurethane (PU) to make the material water-repellent and durable. The use of PU means these materials are not fully biodegradable, as opposed to animal leather.
Van der Leest is exploring whether fungus can replace plastic to make these plant-based leather materials more sustainable.
Aside from testing different types of fungus in the lab, she has designed a speculative brand identity for the future product, which she calls Fungkee.
“To take a biomaterial and coat it with PU, which of course is plastic, doesn’t really make sense to me,” said Van der Leest. “In nature there are all kinds of different waterproof coatings, on leaves, on mushrooms, on the shields of insects, I made it my goal to find a fungus that could coat this material.”
Based on initial results from, Van DER Leest expects a product could be developed in the next five to 10 years. Van der Leest is developing the concept along with cell biologist Aneta Schaap-Oziemlak. In 2019, they received the Bio Art & Design Award, a €25,000 prize that helped their research take off.
For the initial tests, Van der Leest chose a specific type of bio-leather made from bacterial cellulose. This material is grown by cultivating bacteria and yeast in a vat of liquid.
The concept developed by Van der Leest and Schaap-Oziemlak is for a fungal coating that actually wraps the cellular structure, and not only covers the material. The coating is created by cultivating mycelium spores in liquid and have found one particular fungus that gave them the result they were looking for.
“We saw fungal strains growing invasively through the material, which was a good sign,” said Van der Leest. “They weren’t biodegrading the material, they were using it as a kind of home. That was one of our goals.”
The designer hopes for the coating to be used both by industry and consumers. She hopes to be able to replace PU in bio-leathers as well as in other textiles, like tent fabric.
“It’s very interesting to see how you can develop materials or products that are more natural, but with the help of modern science you can scale them,” she added.