Citation: Sydor, M.; Cofta, G.; Doczekalska, B.; Bonenberg, A. Fungi in Mycelium-Based Composites: Usage and Recommendations. Materials 2022, 15, 6283. https:// doi.org/10.3390/ma15186283 Academic Editors: Miha Humar, Christian Brischke and Ilze Irbe Received: 5 August 2022 Accepted: 5 September 2022 Published: 9 September 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). materials Review Fungi in Mycelium-Based Composites: Usage and Recommendations Maciej Sydor 1, * , Grzegorz Cofta 2 , Beata Doczekalska 2 and Agata Bonenberg 3 1 Department of Woodworking and Fundamentals of Machine Design, Faculty of Forestry and Wood Technology, Pozna´ n University of Life Sciences, 60-637 Pozna ´ n, Poland 2 Department of Chemical Wood Technology, Faculty of Forestry and Wood Technology, Pozna ´ n University of Life Sciences, 60-637 Pozna ´ n, Poland 3 Institute of Interior Design and Industrial Design, Faculty of Architecture, Poznan University of Technology, 60-965 Pozna ´ n, Poland * Correspondence: maciej.sydor@up.poznan.pl; Tel.: +48-618466144 Abstract: Mycelium-Based Composites (MBCs) are innovative engineering materials made from lignocellulosic by-products bonded with fungal mycelium. While some performance characteristics of MBCs are inferior to those of currently used engineering materials, these composites nevertheless prove to be superior in ecological aspects. Improving the properties of MBCs may be achieved using an adequate substrate type, fungus species, and manufacturing technology. This article presents scientifically verified guiding principles for choosing a fungus species to obtain the desired effect. This aim was realized based on analyses of scientific articles concerning MBCs, mycological literature, and patent documents. Based on these analyses, over 70 fungi species used to manufacture MBC have been identified and the most commonly used combinations of fungi species-substrate-manufacturing technology are presented. The main result of this review was to demonstrate the characteristics of the fungi considered optimal in terms of the resulting engineering material properties. Thus, a list of the 11 main fungus characteristics that increase the effectiveness in the engineering material formation include: rapid hyphae growth, high virulence, dimitic or trimitic hyphal system, white rot decay type, high versatility in nutrition, high tolerance to a substrate, environmental parameters, susceptibility to readily controlled factors, easy to deactivate, saprophytic, non-mycotoxic, and capability to biosynthesize natural active substances. An additional analysis result is a list of the names of fungus species, the types of substrates used, the applications of the material produced, and the main findings reported in the scientific literature. Keywords: mycelium; fungi; biomaterial; bio-composite; bio design; mycelium-based material; mycelium-based composites; biopolymers; wood 1. Introduction Mycelium-Based Composites (MBC) consist of defragmented lignocellulosic particles bonded with dense chitinous mycelium. These innovative biomaterials show eco-friendly characteristics: waste materials usage, low energy demand during production, the produc- tion does not generate waste, and the products are readily recycled [1]. The performance properties of MBC are usually inferior to those of the materials used so far. However, their advantages are revealed in some areas, such as high acoustic attenuation, fire resistance, the absence of harmful synthetic chemical components [2–4], and advantages connected with aesthetics. In turn, the drawbacks of MBC, which need to be eliminated, include excessive hygroscopicity, low tensile strength, susceptibility to biological corrosion, and the need to deactivate the fungus. Improving the properties of this innovative material is the goal of many scientific and commercial endeavors [5,6]. Thus, the potential applications of MBC may be found in architecture [7,8], packaging [9], the automotive industry [10], as a furniture material, in art [8], and in manufacturing various chitin- and β-glucan-based Materials 2022, 15, 6283. https://doi.org/10.3390/ma15186283 https://www.mdpi.com/journal/materials