Bracket fungi grow on trees, decomposing cellulose and in some cases lignin of their hosts. A common European species is Fomes fomentarius, also known as tinder fungus. The hoof-shaped fruit body has a hard, wood-like top surface. At the bottom, pores are visible; these pores extend from the trama below the top surface towards the bottom. They are formed by an interconnected network of hyphens; thus, their walls consist of a chitin network. The fruit body encloses the myecellium where the hyphens connect the fungus to the wood. The fruit bodies are very strong and tough, and the connection to he tree is strong enough to even carry the body weight of an adult human. Biotechnology offers a variety of techniques to grow the fungi and gene-modified versions in vitro on different substrates, e.g. cellulose-containing straw. Therefore, with native or genetically modified fungi that contain defined hyphen networks, light and strong composite materials can be designed that are moreover biodegradable after use .
Here, we report on microstructural and mechanical tests on the fruit bodies of Fomes fomentarius and on first composite structures made from different bracket fungi grown on a variety of substrates. In the wet stage, and if loaded parallel to the long axis of the tubes, the fruit body of the fungi behaves foam-like with a high proportion of viscoelastic recovery after unloading. We observed buckling and splitting of the tube walls in deformation bands as main damage mechanism. In the dry state, the material behaves much more brittle. The composite specimens were loaded in compression or bending. They exhibited a benign failure behaviour, due to crack diversion on interfaces and entangling of fibres of the reinforcing substrate. Our results show that bracket fungi reinforced with natural fibrous materials are promising damage-resistant light weight materials. The properties can be tuned by adapting the fungus/substrate-ratio, by creating layered structures, and by optimising the size of the reinforcing particles
 Mind the fungi: www.mikrobiologie.tu-berlin.de/menue/forschung/mind_the_fungi.