Researchers have harnessed fungus to convert food waste into sustainable faux leather, as well as paper products and cotton substitutes, with properties comparable to the traditional materials. This fungal leather takes less time to produce than existing substitutes already on the market, and, unlike some, is 100% biobased.
Who did it: Akram Zamani of the University of Borås in Sweden led researchers on this project. This research was recently presented at a meeting of the American Chemical Society.
How it worked: The researchers collected unsold supermarket bread, which they dried and ground into breadcrumbs. They mixed the breadcrumbs with water in a pilot-scale reactor and added spores of Rhizopus delemar, which can typically be found on decaying food.
- As this fungus fed on the bread, it produced microscopic natural fibres made of chitin and chitosan that accumulated in its cell walls.
- After two days, the scientists collected the cells and removed lipids, proteins and other byproducts that could be used in food or feed. The remaining jelly-like residue consisting of the fibrous cell walls was then spun into yarn, which could be used in sutures or wound-healing textiles and perhaps in clothing.
- Alternatively, the suspension of fungal cells was laid out flat and dried to make paper- or leather-like materials. The first prototypes of fungal leather the team produced were thin and not flexible enough.
- Now the group is working on thicker versions consisting of multiple layers to more closely mimic real animal leather. These composites include layers treated with tree-derived tannins — which give softness to the structure — combined with alkali-treated layers that give it strength. Flexibility, strength and glossiness were also improved by treatment with glycerol and a biobased binder.
- While some other fungal leathers have already reached the market, little information about their production has been published, and their properties don’t yet match real leather. The commercial products are made from harvested mushrooms or from fungus grown in a thin layer on top of food waste or sawdust using solid state fermentation. Such methods require several days or weeks to produce enough fungal material, whereas this fungus is submerged in water and takes only a couple of days to make the same amount of material. A few other researchers are also experimenting with submerged cultivation but at a much smaller scale than her group’s efforts.
- In addition, some of the fungal leathers on the market contain environmentally harmful coatings or reinforcing layers made of synthetic polymers derived from petroleum, such as polyester.
What next: Zamani's team is working to further refine their fungal products. They also recently began testing other types of food waste, including fruits and vegetables. One example is the mass left after juice is pressed from fruit. The researchers acknowledge support and funding from Vinnova.
In the reseacher's words:
We hope they can replace cotton or synthetic fibres and animal leather, which can have negative environmental and ethical aspects. In developing our process, we have been careful not to use toxic chemicals or anything that could harm the environment. Our recent tests show the fungal leather has mechanical properties quite comparable to real leather.
—Akram Zamani
University of Borås in Sweden
