Mycelium-based compounds are synthesized with different types of fungi, especially mushrooms.[38] The selection of fungal species is essential to determine the specific properties of the final product. Species such as G. lucidum, Ganoderma sp. P. ostretus, Pleurotus sp., T. versicolor, Trametes sp., etc.[39].
Fungi are capable of degrading and colonizing different types of organic substances to form compounds. One of the most used organic substrates in mycelium compounds is plant residues. When the fungal mycelium colonizes and degrades these organic compounds, a dense network of hyphae forms.
To produce sustainable alternatives, especially for petroleum-based materials, fungal mycelium is incubated with a plant waste product. It is important that the mycelium and organic substrate are incubated correctly, as it is during this period that these particles interact with each other and come together to form a compound. During this time, the mycelium uses essential nutrients such as carbon, minerals and water from the plant waste product.
The organic substrate used can be varied and include cotton, wheat grain, rice husk, sorghum fiber, agricultural waste, sawdust, bread particles, banana peel, coffee residue, among others. To synthesize and manufacture the compounds, different techniques are used, such as adding carbohydrates, altering fermentation conditions, using different manufacturing technologies, altering post-processing steps, and genetic or biochemical modification to form products with certain properties.[38].
Most mycelium compounds are manufactured in plastic molds, so that the mycelium is grown directly into the desired shape.[40][39] Other manufacturing methods use laminated skin molds, vacuum skin molds, glass molds, wood molds, plywood molds, petri dish molds, mosaic molds, etc.[39] During the manufacturing process, it is crucial to have a sterile environment, controlled light conditions, temperatures between 25 to 35 °C and humidity between 60 to 65% to obtain the best results.[40] Another way to synthesize a mycelium composite is by mixing different proportions of fibers, water and mycelium and then placing them in PVC molds in layers that are then compressed and incubated for a few days.[41] Mycelium composites can be processed into foam, laminate and mycelium sheet using processing techniques such as laser cutting, cold and heat compression, etc.[40][39] Mycelium compounds tend to absorb water once manufactured, however, this property can be removed by drying the product in the oven.[39].
One of the advantages of using mycelium compounds is that the properties can be modified depending on the manufacturing process and the variation of the fungal species used, since the properties depend on the type of fungus used and the place where they are grown.[39] In addition, fungi are capable of degrading plant cellulose to make compounds in a preferable way.[3] Some important mechanical properties, such as compressive strength, morphology, tensile strength, hydrophobicity and flexural strength, They can also be modified for different uses of the composite.[39] To increase tensile strength, the composite can be subjected to thermal pressing.[38] The type of substrate used also affects the properties of the material; For example, a mycelium composite made from 75% rice hulls has a density of 193 kg/m, while 75% wheat grains have 359 kg/m.[3] Another way to increase the density of the composite is by deleting a hydrophobin gene.[39] These compounds are also capable of self-fusion, which increases their strength.[39] Mycelium materials are typically compact, porous, and lightweight. and good insulators. The main property of these compounds is that they are totally natural and sustainable. Another advantage of mycelium composites is that it acts as an insulator, is flame retardant, non-toxic, water resistant, fast growing and capable of binding to neighboring mycelium products.[42] Mycelium foams and sandwich components are 2 common types of composites.[3] Mycelium foams are the most efficient type due to its low density property, high quality and sustainability.[37] The density of mycelium foam can be decreased by using thinner substrates, with a thickness of less than 2 mm in diameter.[37] These compounds also have greater thermal conductivity.[37].
One of the most common uses of mycelium compounds is as alternatives to petroleum-based materials and polystyrene.[39] These synthetic foams are used for sustainable design and architectural products. The use of mycelium compounds is based on their properties. There are several bio-sustainable companies such as Ecovative Design LLC"), MycoWorks"), MyCoPlast"), etc. that use mycelium compounds as protective packaging for electronics and food, bricks, leather substitutes, alternatives for flooring and acoustic tiles, thermal and acoustic insulation, building panels, etc.[39] The ability to bond with neighboring compounds is used to help the mycelium compound form strong bonds to join bricks.[42] An example is Hy-Fi, a 12-meter-high tower at MoMA PS1 in New York, built with 1,000 bricks of corn stalks and mycelium.[43] This tower won the annual Young Architects Program competition in 2014.[43]
There are also other everyday products such as lamps, kitchen utensils, ceiling lights, decorative items, fashion items, chairs, and others made from mycelium.[42] In architecture, mycelium compounds are widely used for their better performance as insulation and greater fire resistance than other products.[39] Mycelium is increasingly used in industry to replace plastic materials that are harmful to the environment. Manufactured using a low energy natural process and are biodegradable.[44].