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The transition from a linear to a circular economy is urgently needed to mitigate environmental impacts and loss of biodiversity. Among the many potential solutions, the development of entirely natural-based materials derived from waste is promising. One such material is mycelium-bound composites obtained from the growth of fungi onto solid lignocellulosic substrates, which find applications such as insulating foams, textiles, packaging, etc. During growth, the fungus degrades and digests the substrate to create a web-like stiff network called mycelium. The development of the mycelium is influenced by several factors, including the substrate composition. As food waste accounts for nearly 44% of total municipal solid waste, incorporating food in the substrate composition could be a means to increase the nutrients absorbed by the fungus. In this paper, we study the effects of the addition of food supplements on the growth of two fungal species, Ganoderma lucidum and Pleurotus ostreatus. The substrates, the food supplements, and the mycelia are characterized using Fourier-transform infrared spectroscopy, scanning electron microscopy, and optical microscopy. Our results show that addition of barley as a supplement significantly boosts the growth of G. lucidum and P. ostreatus. Using a common food as a nutritious enrichment for the development of mycelium is a simple and straightforward strategy to create waste-based mycelium-bound biocomposites for a large range of applications, on-site, therefore promoting a circular economy., Competing Interests: The authors have read the journal’s policy and have the following potential competing interests: The research was conducted at the Future Cities Laboratory at the Singapore-ETH Centre and at Nanyang Technological University. The authors acknowledge the Facility for Analysis, Characterization, Testing, and Simulation, Nanyang Technological University, Singapore for the use of their electron microscopy facilities. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

Current environmental crisis calls for new sustainable materials and products. Mycelium-based materials are grown by fungi onto solid ligno-cellulosic substrates and are promising sustainable materials which still face barriers to entry. This review discusses the challenges and prospects for making mycelium products. First, the technical challenges, properties needs and scientific knowledge gaps are reviewed. Then, methods to tailor the performance of mycelium-based materials are proposed, using synthetic or natural means. Living mycelium-based materials are also considered as an interesting alternative. The potential market opportunities for these products and their distribution are also discussed along with the public acceptance and perception. Overall, this paper complements current reviews on mycelium materials fabrication and properties by highlighting key gaps and challenges to address to allow these materials to enter the market. The paper suggests directions of future research and development for including mycelium-based products in daily life and improving the sustainability of the materials commonly used and their production. • One barrier to entry for mycelium products is their biodegradability. • Mycelium products could be made competitive thanks to their biodegradability. • Mycelium materials' properties can be tailored using synthetic or natural means. • Mycelium-based materials can also be used as living engineering materials. • Positive public perception could increase by adopting holistic views of the world. [ABSTRACT FROM AUTHOR]

[Display omitted] • Single fungal hyphae increase in stiffness with time, up to 5 GPa. • Increase in mycelium density increases the mechanical properties of the composite. • Woodpiles porous structures lead to increased dense mycelium skin growth. • Woodpiles porous structures increase the stiffness by 6 times after 28 days mycelium growth. • Structural design in porous structure is an efficient method to improve the properties of growing bio-based materials. Mycelium-bound composites are biodegradable, eco-friendly materials grown by fungi onto solid ligno-cellulosic substrates. Mycelium is an interconnected network made of fungal cells that bind the substrates' particulates together. Uncompressed mycelium-bound composites have typically weak mechanical properties, similar to that of expanded polystyrene. In this paper, mycelium is grown onto porous woodpile struts structures to increase the final mechanical properties. The hypothesis is that increase in porosity can increase oxygen diffusion throughout the material and increase the development of dense mycelium network. Mycelium-bound composites grown from P. ostreatus onto bamboo microfibers substrates were studied to test this hypothesis. Constructing porous woodpile structures and monitoring the growth and the mechanical properties under compression, it was found that the porosity obtained through the design was able to increase dense fungal mycelium skin formation. As a result, the stiffness of the porous structures was multiplied by 6 after 28 days of growth. The specific modulus was in turned multiplied by 4 with the addition of 30 % macroscopic porosity. Despite the modest mechanical properties (stiffness about 0.5 MPa), the approach proposed illustrates how appropriate structural design can efficiently increase the properties of grown bio-based materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • An organic waste-based ink was developed for 3D printing of mycelium-based engineered living materials (ELMs) in non-sterile conditions. • Mycelium growth and density improves with increasing nutrient content, which improves the mechanical strength of the 3D printed structure. • 3D printed mycelium-based ELMs exhibit self-healing behaviour. • 3D printed mycelium-based ELMs have the potential to act as a glue, joining different compatible materials together. There is an urgent need to change the way society produces and fabricates materials. Among the sustainable processes developed to date, 3D printing enables limited generation of waste. Living materials that are grown by microorganisms are also an interesting approach to fabricate biodegradable materials sustainably. 3D printing of living materials is nevertheless challenged by a high barrier to entry due to stringent sterilization requirements. In this study, the authors use a waste ingredient, coffee grounds, to fabricate mycelium materials using 3D printing in ambient conditions. Mycelium is the vegetative parts of the fungi which forms an interconnected network, covering air-material interfaces with a dense skin. An agar gel was chosen as the printing medium and supplemented with coffee grounds, malt and peptone to double the growth rate and density of the mycelium by Pleurotus ostreatus. Despite the jelly nature of the agar-based ink, 3D printing with a resolution of about 1 mm could be achieved using direct ink writing. The growth of the mycelium embedded in the ink was studied over 28 days and demonstrated that the mycelium was efficient in reinforcing the printed part, doubling its compressive modulus up to 60 kPa. Furthermore, the objects created by this ink exhibit self-healing and can be used for gluing components together. The approach taken in this work could be adapted by the user to accommodate for functionality requirements and the available local resources, thereby addressing some of the most pressing sustainable development goals. [ABSTRACT FROM AUTHOR]

Mycelium-bound composites are promising materials for sustainable packaging, insulation, fashion, and architecture. However, moulding is the main fabrication process explored to date, strongly limiting the ability to design the complex shapes that could widen the range of applications. Extrusion is a facile and low energy-cost process that has not yet been explored for mycelium-bound composites with design freedom and structural properties. In this study, we combine cheap, easily and commonly available agricultural waste materials, bamboo microfibres, chitosan, and mycelium from Ganoderma l ucidum, to establish a composite mixture that is workable, extrudable and buildable. We study the impact of bamboo fibre size, chitosan concentration, pH and weight ratio of bamboo to chitosan to determine the optimum growth condition for the mycelium as well as high mechanical stiffness. The resulting materials have thus low energy costs, are sustainable and can be shaped easily. The developed composition is promising to further explore the use of mycelium-bound materials for structural applications using agricultural waste. Unlabelled Image • Mycelium-bound composites are sustainable alternative to current composites used in architecture, for example. • Having an extrudable composition to build mycelium-bound composites allows complex shaping and designing. • Chitosan addition to bamboo fibres provides workability, extrudability and buildability while allowing mycelium growth. [ABSTRACT FROM AUTHOR]