Handbags that are fashioned from “leather” made from a fungus, are going to be the trend in the forthcoming days. At present, scientists explain how they have controlled this organism to transform food waste into tenable faux leather, as well as paper products and cotton substitutes, with properties equivalent to the conventional materials.
Fungal fibers can be turned into yarn (left) or a leather substitute (right). Image Credit: Akram Zamani.
The researchers state that less time is required to produce the fungal leather compared to present substitutes available on the market, and, unlike some, it is 100% biobased.
The scientists will present their outcomes at the spring meeting of the American Chemical Society (ACS). ACS Spring 2022 is a hybrid meeting that is being held virtually and in-person (March 20–24), with on-demand access available (March 21 to April 8). The meeting features over 12,000 presentations on an extensive range of science topics.
Cotton supplies are diminishing, and, like petroleum-based textiles and leather, its production is linked to environmental concerns. At the same time, plenty of food gets wasted. Akram Zamani, PhD., set out to solve such unrelated issues with new biobased and sustainable materials derived from fungi.
We hope they can replace cotton or synthetic fibers 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.
Akram Zamani, Project Principal Investigator, University of Borås
Fungi eat, just like humans. For the organisms to be fed, the team gathered unsold supermarket bread, which was dried and ground into breadcrumbs. The breadcrumbs were mixed with the water in a pilot-scale reactor and added spores of Rhizopus delemar. This can normally be found on decaying food.
This fungus fed on the bread, and it generated microscopic natural fibers made of chitin and chitosan that collected in its cell walls. After two days, the scientists gathered the cells and eliminated proteins, lipids and other byproducts that could be utilized in food or feed.
The leftover jelly-like residue comprising the fibrous cell walls was further spun into yarn. This could be utilized in sutures or wound-healing textiles and probably in clothing.
Alternatively, the fungal cells’ suspension was laid out flat and dried to make paper- or leather-like materials. The fungal leather prototypes produced by the team were thin and not sufficiently flexible, stated Zamani, who is at the University of Borås in Sweden.
Currently, the group is working on thicker versions comprising multiple layers to more closely mimic actual animal leather. Such composites consist of layers treated with tree-derived tannins—which makes the material soft. This has been integrated with alkali-treated layers that give it strength. Also, strength, flexibility, and glossiness were enhanced by treatment with a biobased binder and glycerol.
Our recent tests show the fungal leather has mechanical properties quite comparable to real leather.
Akram Zamani, Project Principal Investigator, University of Borås
For example, the relation between density and Young’s modulus, which quantifies stiffness, is the same for the two materials.
According to Zamani, while a few other fungal leathers have reached the market already, little information regarding their production has been reported, and their properties do not yet match real leather.
From what Zamani can ascertain, the commercial products are created from harvested mushrooms or fungus grown in a thin layer on top of sawdust or food waste utilizing solid state fermentation.
These techniques need several days or weeks to generate sufficient fungal material, whereas her fungus has been soaked in water and takes only a couple of days to create the same amount of material. Also, a few other scientists are experimenting with submerged cultivation but at a much smaller scale compared to the measures taken by her group.
Some of the fungal leathers available on the market today contain reinforcing layers or environmentally harmful coatings made of synthetic polymers derived from petroleum, like polyester. That differs from the University of Borås team’s products, consisting solely of natural materials and will thus be biodegradable, expects Zamani.
Zamani’s team is working to refine their fungal products further. Also, they recently started testing other types of food waste, such as vegetables and fruits, such as the mass left over after fruit has been pressed to make juice.
Instead of being thrown away, it could be used for growing fungi. So we are not limiting ourselves to bread, because hopefully there will be a day when there isn’t any bread waste.
Akram Zamani, Project Principal Investigator, University of Borås
The researchers acknowledge financial support from Vinnova.
New textiles from bread waste
Video Credit: American Chemical Society.
Source: https://www.acs.org/content/acs/en.html