(Nanowerk Spotlight) Mushrooms have long been a staple in the culinary world, but their role in the sustainability movement is rapidly expanding. With global mushroom production reaching over 48 million tons in 2022, this thriving industry produces a significant amount of waste. From discarded mushroom stems to the substrate left behind after harvest, a staggering volume of mushroom by-products accumulates each year. Traditionally, these by-products have been underutilized, often relegated to low-value uses like compost or biofuel. However, recent advances in material science are poised to change that, offering innovative ways to transform this waste into valuable, sustainable materials.
In recent years, the quest for eco-friendly materials has intensified. Single-use plastics and other non-biodegradable materials dominate industries such as cosmetics, packaging, and environmental cleanup. Their environmental impact, particularly their contribution to pollution and waste, has led researchers to explore alternatives that can offer similar functionality without the lasting ecological footprint. This backdrop of environmental concern has driven interest in finding new uses for agricultural by-products, including those from the mushroom industry.
Mushroom residues (MR), which include discarded stems and caps, and spent mushroom substrate (SMS), the nutrient-rich material left after mushroom harvest, are two abundant by-products. Together, they offer a promising source of raw material for creating functional, biodegradable products. The challenge has been finding ways to harness their natural properties in a way that adds value and meets the demands of modern applications.
This is where the work of researchers in Sweden comes in. Their study, published in Advanced Functional Materials (“Fungal Innovation: Harnessing Mushrooms for Production of Sustainable Functional Materials”), have focused on transforming MR and SMS into useful products like flexible sheets for cosmetics, rigid materials for packaging, and foams for oil spill remediation. These innovations offer a way to not only reduce waste in mushroom farming but also provide sustainable alternatives to conventional materials in key industries.
A general overview of the concept for the development of advanced functional materials from by-products of the mushroom industry – mushroom residue (MR) and spent mushroom substrate (SMS), targeting cosmetics (flexible sheet), packaging (rigid sheet), and sorption (foam) applications. The researchers demonstrated that by harnessing the natural characteristics of bioresources and using innovative technologies, advanced functional materials with specific properties for their intended applications can be developed. (Reprinted from DOI:10.1002/adfm.202412753, CC BY)
One of the most exciting aspects of this research is the development of flexible, bioactive sheets from mushroom residues. The fruiting bodies of mushrooms, particularly the white button mushroom (Agaricus bisporus) and lion’s mane mushroom (Hericium erinaceus), are rich in compounds like chitin and glucan. Chitin is a strong, fibrous polymer that forms part of the cell walls in fungi and provides mechanical strength, while glucan adds flexibility and toughness. Together, they create a natural composite material that is ideal for producing flexible sheets, such as those used in cosmetic face masks.
To extract these valuable polymers, researchers experimented with different methods. One approach involved using water to extract the chitin-glucan complex, preserving many of the bioactive compounds naturally present in the mushrooms. Another method used sodium hydroxide (NaOH) to strip away non-structural components, leaving a purer form of the chitin-glucan. While the NaOH extraction yielded stronger sheets, the water extraction retained more of the antioxidants, making these sheets particularly well-suited for cosmetic applications.
The properties of the resulting sheets were impressive. The researchers found that the sheets made using water extraction had higher tensile strength than those created with NaOH, making them both durable and flexible – key qualities for use in face masks. Moreover, these fungal-based masks exhibited antioxidant activity of up to 94%, which could potentially benefit the skin by protecting it from oxidative stress. This natural bioactivity, combined with the mechanical properties, suggests that mushroom-based face masks could be a sustainable alternative to the cotton and synthetic fiber masks currently dominating the market.
In addition to cosmetic applications, the researchers explored the potential of SMS to create rigid, durable materials. SMS consists mainly of cellulose, hemicellulose, and lignin—components commonly found in wood. By processing SMS using ultrafine grinding or twin-screw extrusion, the researchers were able to create sheets with varying properties. The grinding method produced dense, strong sheets, while extrusion resulted in lighter, more porous materials. Both processes reduced the size of the SMS fibers, allowing them to be formed into rigid sheets suitable for packaging applications.
The SMS-derived sheets demonstrated good mechanical strength and were comparable to polylactic acid (PLA), a common bioplastic used in packaging. Not only were the SMS sheets strong, but they also exhibited antioxidant properties, which could enhance their value as bioactive packaging materials. Furthermore, these sheets had a low oxygen permeability, making them suitable for packaging products that are sensitive to oxidation, such as food and pharmaceuticals.
Another remarkable application of SMS is in the creation of foams for oil spill remediation. The porous structure of SMS, combined with its amphiphilic nature—meaning it can absorb both oil and water—makes it an excellent material for cleaning up environmental pollutants. The researchers developed foams from SMS that could absorb up to 28 times their weight in oil while maintaining structural integrity. This property is crucial for effective oil spill clean-up, as many conventional sorbents degrade or lose their structure after absorbing oil. Unlike synthetic materials, SMS foams are biodegradable, meaning they won’t contribute to microplastic pollution if they are left in the environment.
The potential environmental impact of these SMS foams is significant. Oil spills are a major environmental hazard, with long-lasting effects on ecosystems. Current oil sorbents, often made from synthetic materials, can address the immediate problem but create their own waste issues. A biodegradable sorbent like SMS foam offers a more sustainable solution that can help mitigate the damage without adding to the problem.
Overall, this research demonstrates the untapped potential of mushroom farming by-products. Through relatively simple processing techniques, these by-products can be transformed into high-value, sustainable materials that address real-world needs. The ability to produce flexible sheets for cosmetics, rigid sheets for packaging, and foams for environmental remediation highlights the versatility of mushroom-derived materials.
The implications of this work extend far beyond the mushroom industry. As the world continues to grapple with environmental challenges, including plastic pollution and resource scarcity, the development of bio-based, biodegradable materials will be critical. The work of these researchers shows that even materials typically considered waste can become part of the solution. By transforming mushroom residues and spent substrate into functional materials, they not only reduce agricultural waste but also contribute to a more sustainable future.
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