Empa researchers develop bio-based packaging material from mycelium

In Switzerland, sustainably produced, biodegradable materials are an important focus of modern materials science. However, when working natural materials such as cellulose, lignin or chitin, researchers face a trade-off. Although these substances are biodegradable in their pure form, they are often not ideal when it comes to performance. Chemical processing steps can be used to make them stronger, more resistant or more supple – but in doing so, their sustainability is often compromised.

Empa researchers from the Cellulose and Wood Materials laboratory have now developed a bio-based material that cleverly avoids this compromise. Not only is it completely biodegradable, it is also tear-resistant and has versatile functional properties. All this with minimal processing steps and without chemicals – you can even eat it.

As the basis for their novel material, the researchers used the mycelium of the split-gill mushroom, a widespread edible fungus that grows on dead wood. Mycelia are root-like filamentous fungal structures that are already being actively researched as potential sources of materials. Normally, the mycelial fibers – known as hyphae – are cleaned and, if necessary, chemically processed, which brings about the above-mentioned trade-off between performance and sustainability.

The Empa researchers chose a different approach. Instead of treating the mycelium, they use it as a whole. As it grows, the fungus not only forms hyphae, but also a so-called extracellular matrix: a network of various fiber-like macromolecules, proteins and other biological substances that the living cells secrete. “The fungus uses this extracellular matrix to give itself structure and other functional properties. Why shouldn’t we do the same?” explains Empa researcher Ashutosh Sinha. “Nature has already developed an optimized system,” adds Gustav Nyström, head of the Cellulose and Wood Materials lab.

With a bit of additional optimization, the researchers gave nature a helping hand. From the enormous genetic diversity of the split-gill, they selected a strain that produces particularly high levels of two specific macromolecules: the long-chain polysaccharide schizophyllan and the soap-like protein hydrophobin. Due to their structure, hydrophobins collect at interfaces between polar and apolar liquids, for example water and oil. Schizophyllan is a nanofiber: less than a nanometer thick, but more than a thousand times as long. Together, these two biomolecules give the living mycelium material properties that make it suitable for a wide range of applications.