The construction industry makes a significant contribution to global CO₂ emissions. Material extraction, processing, and demolition account for most of its environmental impact. As a response, there is an increasing interest in developing and implementing innovative biomaterials that support a circular economy, such as mycelium-based composites. The mycelium is the network of hyphae of fungi. Mycelium-based composites are renewable and biodegradable biomaterials obtained by ceasing mycelial growth on organic substrates, including agricultural waste. Cultivating mycelium-based composites within molds, however, is often wasteful, especially if molds are not reusable or recyclable. Shaping mycelium-based composites using 3D printing can minimize mold waste while allowing intricate forms to be fabricated. In this research, we explore the use of waste cardboard as a substrate for cultivating mycelium-based composites and the development of extrudable mixtures and workflows for 3D-printing mycelium-based components. In this paper, existing research on the use of mycelium-based material in recent 3D printing efforts was reviewed. This review is followed by the MycoPrint experiments that we conducted, and we focus on the main challenges that we faced (i.e., contamination) and the ways in which we addressed them. The results of this research demonstrate the feasibility of using waste cardboard as a substrate for cultivating mycelia and the potential for developing extrudable mixtures and workflows for 3D-printing mycelium-based components.

Aims To investigate characterization of the bacterial community composition and functionality and their impact on substrate biodegradation as well as mushroom yield. Methods and Results Bacterial diversity, composition and functionality were accessed by DNA-derived analysis for a sugarcane straw-based substrate composted for either 5, 10 or 15 days. In addition, carbon and nitrogen losses, carbohydrate conversion and mushroom yields were measured for the different treatments. Changes were observed in the bacterial community diversity and composition after the process started, but not during the composting process itself. Following phase I, Acinetobacter sequences were recovered in high numbers, and selected genes associated with nitrogen metabolism and lignocellulose deconstruction were mapped. Substrate physicochemical composition showed elevated carbon and nitrogen losses after 10 and 15 days of phase I with reductions in mushroom yield. Conclusions Acinetobacter species appear to play an important role in substrate degradation processes, and a 5-day phase I period showed a significant higher mushroom yield compared to composting for either 10 or 15 days. Significance and Impact of the Study This study confers a better understanding of the bacterial community manipulation during the substrate preparation and their influence in substrate selectivity for the Pleurotus ostreatus cultivation.

There is growing interest in microbiome-based management approaches for plant and animal health and sustainable agricultural practices. To our knowledge, there are no descriptions of Agaricus bisporus mushroom developmental patterns using such an approach. Here, we utilized substrate passaging to select for devomes (developmental microbiomes) in either compost or casing material that resulted in earlier developing (best performing experimental units with a higher number of primordia at day 10 of cultivation) mushrooms compared to unpassaged controls. Passaged casing showed earlier pinning (fruiting body formation), while passaged compost delayed fruiting body formation. Despite changes in pin emergence for passaged substrates and higher mushroom yield in the passaged casing’s first harvest, the total mushroom yield in 24 days of crop cycle did not change significantly. The bacterial communities were distinct between compost and casing materials, but in both microenvironments, the alpha diversity tended to increase and stabilize over time in standard and passaged substrates. Community composition within compost and casing microenvironments tended to be more homogenous after colonization of the fungus. Passaging of casing increased the bacterial alpha diversity and shifted community composition. Such changes were not observed in passaged compost. Some bacterial taxa were enriched or depleted by passaging, e.g., Pseudomonas spp. (hypothesized as a stimulus to A. bisporus fructification) were depleted in passaged compost and casing. Overall, this work presents an experimental approach to manipulate compost and casing microbial communities with the potential to be combined with currently employed cultivation strategies toward a more sustainable mushroom cultivation system. IMPORTANCE: Agaricus bisporus is an economically important edible mushroom and manipulating its developmental patterns is crucial for maximizing yield and quality. One of the potential strategies for achieving such a goal is passaging microbial communities in compost or casing. The current study demonstrated that passaging substrates develop enriched microbial communities, and after a few passages, certain levels of changes in mushroom developmental patterns (the timing of fruiting bodies formation) were observed as well as shifts in the bacterial communities. Overall, a better understanding of the complex interactions between microorganisms present in the cultivation system may help farmers and researchers to develop more efficient and sustainable cultivation practices that can both benefit the environment and human health.