Fungal materials make leather
Dr Michael Ford MIMMM at Haseltine Lake Kempner explores a patent for an artificial leather material made from mushrooms.
Humans having been producing leather in essentially the same way for thousands of years – by tanning animal skins and hides.
More recently, artificial leather – sometimes known as vegan leather or pleather – has been growing in popularity due to concerns about animal welfare, religious sensitivities, cost and environmental impact, including the carbon footprint of cattle-rearing and the use of pollutants in the tanning process.
However, artificial leather is not without its downsides. It is often manufactured using fossil fuel-derived products such as polyurethanes, and so is not necessarily environmentally friendly or carbon-neutral. Many synthetic leather substitutes can also be difficult to recycle and do not decompose when disposed in landfill.
Accordingly, there is significant interest in producing replacements for leather that avoid both animal and fossil-fuel-derived products.
In March 2024, UK-based Plant Material Limited was granted European patent EP4308633B1, which describes renewable and biodegradable fungal materials considered suitable for use as leather substitutes. This is due to their high tensile strength, high flexibility and resistance to water damage.
According to the inventors, this represents an improvement over known materials produced from fungal biomass, which typically fail to achieve sufficient tensile or compressive strength and suffer from high levels of water solubility and susceptibility to moisture damage.
More specifically, the patent claims protection for a fungal material comprising fungal biomass, a polysaccharide-based matrix, a plasticiser, an emulsifying agent, and optionally a diluent.
The plasticiser comprises latex and/or the fungal material comprises a support material selected from cotton, polyester, nylon, denim and/or silk.
According to the patent, the concentration of the polysaccharide-based matrix can be adjusted to vary the structural integrity, rigidity and tensile strength of the material, while the plasticiser helps achieve a high degree of flexibility.
The emulsifying agent is included to mitigate increased susceptibility to water damage, which can be caused by the presence of the plasticiser. The inventors posit that the emulsifying agent promotes plasticiser retention by the fungal material, so avoiding leaching of the plasticiser on contact with water.
Latex is chosen as a plasticiser because it appears to improve the material’s flexibility, tensile strength and tear-resistance, while reducing susceptibility to contamination and the required drying time, as well as improving longevity. The patent explains that these properties can be enhanced by using crosslinked latex.
The fungal biomass used can contain at least one of the fungal fruiting bodies (commonly known as mushrooms), fungal mats (also known as fungal biofilms), mycelium (the tangled, root-like structure of a fungus) and hyphae (the individual fungal filaments that make up the mycelium).
The patent suggests various possible fungal genera, including several with edible members such as Boletus (which includes the porcini mushroom) and Cantharellus (which includes the chanterelle or girolle).
Examples given for the polysaccharide-based matrix component include those based on agarose, carrageenan, alginate, cellulose or chitosan, all being natural products or derivatives.
In some cases, the fungal material includes an oil like sunflower oil, rapeseed oil, castor oil or olive oil. This is incorporated to further enhance water repellence and so resistance to water damage.
Experimental examples are included in the patent to illustrate some of the physical properties achievable using fungal materials, based specifically on Agaricus bisporus fruiting bodies (more commonly known as the cultivated mushroom).
The results appear to show, for example, that use of lecithin as an emulsifying agent can counteract increased susceptibility to water damage when glycerol and/or natural latex was included in the mixture as a plasticiser, and that a synergistic effect was also achieved when the emulsifying agent was combined with an oil.
The patent also claims protection for a method of producing the fungal material that involves combining the fungal biomass, a polysaccharide composition capable of forming the polysaccharide-based matrix, the plasticiser, the emulsifying agent and the diluent to produce a fluid mixture and then solidifying this mixture.
In some cases, the method requires melting of the polysaccharide composition before the fluid mixture is solidified. In embodiments where a support material is used, the method can also involve adhering the fungal material to this support material.
In addition to use as a leather substitute, the inventors suggest the fungal material could be used as a plastic substitute, a rubber substitute, an insulation material, a packaging material and even a foodstuff (such as jerky, a chewy sweet or a dog treat).
