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Mycelium-bound composites (MBCs) are materials obtained by growing fungi on a ligno-cellulosic substrate which have various applications in packaging, furniture, and construction industries. MBCs are particularly interesting as they are sustainable materials that can integrate into a circular economy model. Indeed, they can be subsequently grown, used, degraded, and re-grown. Integrating in a meaningful biocycle for our society therefore demands that MBCs fulfil antagonistic qualities which are to be at the same time durable and biodegradable. In this study, we conduct experiments using MBCs made from the fungus species Pleurotus ostreatus grown on bamboo microfibers substrate. By measuring the variations of the mechanical properties with time, we provide an experimental demonstration of a biocycle for such composites for in-door applications. We found that the biocycle can be as short as 5 months and that the use of sustainable coatings is critical to increase the durability of the composites while maintaining biodegradability. Although there are many scenarios of biocycles possible, this study shows a tangible proof-of-concept example and paves the way for optimization of the duration of each phase in the biocycle depending on the intended application and resource availability. [ABSTRACT FROM AUTHOR]

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. [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]