Mechanical, physical and chemical characterisation of mycelium-based composites with different types of lignocellulosic substrates
July 22, 2019
Elise Elsacker Simon Vandelook Joost Brancart Eveline Peeters
PP.1
“The conducted tests reveal that the mechanical performance of the mycelium-based composites depends more on the fibre processing (loose, chopped, pre-compressed, and tow), and size than on the chemical composition of the fibres”
PP.9
“The compressive stiffness is considerably larger for chopped flax, compared to any other fibre type and condition. Chopped fibre substrates result in mycelium composites with slightly higher densities compared to the samples with a loose substrate”
Chopped flax hurds seem a good option to investigated for the jewellery body. Chopped in this paper means blended and passed through a 5mm sieve.
PP.16
“The compressive Young’s modulus is higher for all fibre types in chopped condition since the samples were more dense. Samples containing chopped fibres also showed a more coherent and smoother outer layer. As a compressive material, chopped flax-based samples obviously take the lead (1,18 MPa) compared to the chopped hemp-based samples, which might have been affected by the manufacturing process. Previous studies found that the average compressive strength for cotton down woven mat and hemp pitch woven and non-woven mat substrates varied between 0,67 to 1.18 MPa [4]. However, the samples presented in this paper were not produced with mats but with low-graded hurds. Furthermore, the pre-compression of the samples aimed to improve the compressive mechanical properties of mycelium composites. This fabrication method influenced the composite’s mechanical response in a positive way by increasing the Young’s moduli for every tested fibre type and condition. These findings provide additional support for the hypothesis that precompressed mycelium-composites enhance the mechanical performance [”
A comprehensive framework for the production of mycelium-based lignocellulosic composites
2 April 2020
Elise Elsacker Simon Vandelook Aurélie Van Wylick Joske Ruytinx Lars De Laet Eveline Peeters
PP.2
“A wealth of biological information is available about fungal species, but these are always put in relation with the production of chemicals or enzymes for applications in biofuels, medicine and food. Similarly, an abundance of knowledge exists about lignocellulosic and polymer composites. Yet, a lack of scientific insights and research that place the factors in relation with each other, with the production methods and with the emerging applications of these promising natural composites, prevails.”
“The available literature and knowledge are very fragmented. The methodologies of the published studies are typically different, and no standardized and comparative overview of the production parameters and mechanical properties of mycelium composites exists.”
PP.3
“. Nevertheless, fungal diversity is estimated on 2.2–3.8 millions of species (Hawksworth and Lücking, 2017) with contrasting lifestyles ranging from wood decay over mycorrhizal mutualism to plant and animal (Stajich, 2017). Given the phylogenetic diversity of fungi (Jones et al., 2018), it could be envisaged that there is an unexplored wealth of species with potential to build mycelium materials of superior quality. . Besides investigating diversity of natural strains, genetic engineering can be another approach to improve the application. As an example, a genetically modified strain of Schizophyllum commune resulted in a sterile strain by targeting molecular mechanisms involved in fruiting body formation. This resulted in deleting the unwanted ability of fruiting body and spore formation and on top of that, this mutant strain displayed a 3-fold higher growth speed than wildtype strains (Heath, 1995).”
“Moreover, mycelium can respond to local damage by reinforcing, regrowing and reconnecting neighbouring branches, which is of interest in the production process of mycelium-materials. The strengthening of the branches and the alternation of pathways improves not only the transport capacity of the channels, but also their robustness to damage. Indeed, if the finest hyphae are continuously trimmed, more local branching is stimulated, resulting in an accentuated growth of connections (Gross, 2009). Consequently, damaging or cracking the mycelial network during the growth stimulates the formation of a more robust and denser network, and the regression of other regions to recycle redundant material (Heaton et al., 2010; Falconer et al., 2005; Fricker et al., 2007).”
PP.4*
“Fungal cells have tube-like structures with a complex chemical composition with the cell walls being characterized by layers consisting of extensively cross-linked glucan and chitin components in addition to proteins such as hydrophobins and mannoproteins (Bowman and Free, 2006; NAR et al., 2017). Chitin is a homopolymer of β-(1,4)-linked N-acetylglucosamine, and although it only constitutes a minor part of the entire cell envelope, it greatly contributes to its structural integrity and to that of the organism as a whole (NAR et al., 2017). The Young’s modulus and the tensile strength of pure chitin films vary between 1.2 and 3.7 GPa and 38.3 and 77.2 MPa, respectively, depending on the method of preparation (Ofem et al., 2017). Consequently, the presence of chitin-containing fungal cell walls in mycelial composite materials – even at minor fractions – is crucial for the material’s structural and mechanical properties. As fungal cell walls exhibit a large degree of phenotypical diversity and plasticity (NAR et al., 2017), this contributes to the material’s engineerability.”
“Although limited studies have been performed on how material characteristics alter with the used fungal species or strain (Figs. 3 and 4), they point to an important correlation between (phylo-)genetic nature and mechanical properties which can, among other reasons, be attributed to cell wall composition. For instance, a higher compressive strength and stiffness is found with T. versicolor materi als compared to P. ostreatus (Lelivelt et al., 2015a) (Fig. 3). P. ostreatus-based materials are stiffer (2-fold, E: 28 MPa) than G. lucidum-based (E: 12 MPa) ones. This can be explained by a higher polysaccharides' content in the P. ostreatus-based material (Haneef et al., 2017). G. lucidum, on the other hand, presents a larger elongation at fracture (3-fold, ε: 33%) and higher values in strength (σ: 0.8 MPa) compared to P. ostreatus (ε: 9% and σ: 0.7 MPa) because it consists of a larger amount of proteic and lipid constituents associated with the infrared absorption spectra of the mycelia, which may act as plasticisers. G. lucidum-based materials also display a broader Young’s modulus distribution (Haneef et al., 2017). The tensile properties of non-pressed T. versicolor (σ: 0.04 MPa, E: 4 MPa) compared to P. ostreatus (σ: 0.01 MPa, E: 2 MPa) grown on rapeseed straw are contradicting the properties of heat-pressed T. versicolor (σ: 0.15 MPa, E: 59 MPa) compared to P. ostreatus (σ: 0.24 MPa, E: 97 MPa) (Appels et al., 2018a). The formation of materials with the highest tensile strength can be attributed to S. commune (Appels et al., 2018b) (Fig. 4). The Young’s modulus (E: 913 MPa) and tensile strength (σ: 9.5 MPa) of S. commune wild-type are up to 76 and 9-fold stronger compared to G. lucidum and respectively 33 and 9-fold for P. ostreatus. However, elongation at rupture was up to 23-fold higher for G. lucidum and 6-fold higher for P. ostreatus (Haneef et al., 2017; Appels et al., 2018b).”
PP. 6
“Substrates containing natural fibres that are not degraded during the production of mycelial materials exhibit a strain-hardening behaviour because the natural fibres serve to reinforce and prevent shear failure (Yang et al., 2017). The natural fibres minimise surface cracking during shear measurements and also improve the Young’s modulus and compressive strength (Yang et al., 2017). Research on different types of fibres suggests that the fibre condition influences the compressive Young’s modulus, as chopped hemp fibres (<5 mm) result in a Young’s modulus which is 1.6 times higher than loose hurds (Elsacker et al., 2019) (Fig. 3). Another study indicates that the compressive strength of materials containing natural fibres (wood chips) increases up to 300% when sand or gravel aggregates are mixed, compared to pure materials (Moser et al., 2017”
“Nutritional preferences depend on the used species or strain: for example, when fed on a wood-based substrate, P. ostreatus leaves cellulose almost intact and utilises hemicellulose as the primary energy and carbon source (Chi et al., 2007). Although not always well-described, similar principles regarding feedstock preferences and effects can be expected to govern other fungal species”
PP.7*
“In several studies fungal growth was analysed after using different substrate sterilization methods such as hot water treatment for 30 min, autoclaving at 15 lbs. pressure for 20 min, treatment with formaldehyde solution (50 mL/L water), treatment with bavistin (2 g/L water). It was found that substrates sterilized by autoclaving took less time for spawn run (Kalita, 2015; Atila, 2016)”
PP.11
“High material densities are obtained under a low CO2 concentration and in the absence of light or at a high CO2 concentration in the presence of light (Appels et al., 2018b). Mycelium requires O2 to grow and produces CO2. A low CO2-content is an indication for a basidiomycete that an outside surface is reached, triggering the formation of fruiting bodies. Therefore, the CO2 content should be kept high (Lelivelt et al., 2015a). The Young’s modulus doubles as a result of increased CO2 levels in the light, while the opposite effect is observed in the dark. Similar outcomes are noted with the tensile strength (Appels et al., 2018b)”
“Materials which have grown during an increased period are less porous and therefore result in a decrease of the hydraulic permeability (e.g. 0.40 m2 after 5 days as compared to 0.20 m2 after 25 days) (Ahmadi, 2016). Similarly, the increased period of mycelium growth improves the thermal stability. The best result in the thermal decomposition was obtained after 25 days of mycelial growth, which delayed the onset of thermal decomposition upon exposure to higher temperatures such as 360 °C (Ahmadi, 2016). More extensive incubation times such as 42 days result in a negative impact on the elastic and shear moduli (Yang et al., 2017). This can be explained by the further degradation of the substrate by the fungi, which is otherwise essential to contribute to the elastic stiffness. In contrast, such a long incubation time has a positive impact on the compressive strength with the largest absolute value increase from 350 to 570 kPa, or over 60%, for the pre-incubated in filtered bags and densely packed samples (Yang et al., 2017). As the mycelium continues to grow, the spaces between the fibres are filled, the substrate is bonded more strongly together, and the density is enlarged.”
PP.12
“Both strength and stiffness are improved by infusing a bioresin into the reinforcement skins of the mycelium composite when used as a sandwich structure (Jiang et al., 2017; Jiang et al., 2014). Vacuum infusing processing is therefore an adequate and widely used method (Jiang et al., 2014). However, a wax should be added to the material’s core’s edges to prevent excessive resin absorption; a significant impregnation will result in unfavourable characteristics for a sandwich structure (Jiang et al., 2014).”
“4. How do the material properties impact the applications? The versatility and high potential of the material leads to a broad spectrum of innovative applications and services, which can be classified in different sectors, with the construction and design sector being the most prominent. In addition, the development of mycelium-based materials is also expected to be an important proof-of-concept application in creating societal awareness for the transition to a circular economy”
“Several worldwide active communities of citizen experts discuss and share their experiments, for example, BioFabForum (BioFabForum, n.d.), and Fungal Materials and Biofabrication (Fungal Materials and Biofabrication, n.d.). Such digital platforms are open source databases enabling experts and hobbyists to share inspiration, best-practices and manuals. The domestication of this technology empowers many transdisciplinary collaborations in finding sustainable, ethical, and affordable material solutions for many wasted resources. It nourishes a decentralised manufacturing approach, as a substitute for the complex and moral issues on patents and IP control. Moreover, the richness of an open and distributed approach can be of economic, social and environmental benefit for localities and industry through the rapid diffusion and adoption of the technology (Raworth, 2017). The regenerative potential of circular production here is the creation of various unique local solutions with global open knowledge commons.”
PP. 13/14
“Looking at the feedstock, many lignified plant biomass sources can be used for the production of mycelium-materials. How can natural fibres be engineered to improve the mechanical and physical properties of the material, for example by layering fibre mats or adding supplements such as inorganic components, nutrients or nanoparticles? Since some fungi are known to detoxifying substrates containing aromatic compounds it is feasible to use waste-stream feedstocks containing pollutants and microplastics”
PP 14/15
“Future research in design and architectural practices can concentrate on how the unique temporality of these materials can be deployed as a quality, not as definitive decay, but as a process of regeneration, reintegration in the cycle. How can the properties of living organisms serve as design rules? Furthermore, from the environmental point of view, the material’s sustainability is currently praised but requires however a scientific substantiation”
When the material grows: A case study on designing (with) mycelium-based materials
Elvin Karana Davine Blauwhoff Erik-Jan Hultink Serena Camere
August 2018
International Journal of Design
Engineered mycelium composite construction materials from fungal biorefineries: A critical review
Mitchell Jones
Andreas Mautner
Stefano Luenco
Alexander Bismarck
Sabu John
Materials & Design Volume 187, February 2020, 108397
https://www-sciencedirect-com.ezproxy.hro.nl/science/article/pii/S0264127519308354
Fungi as source for new bio-based materials: a patent review
Kustrim Cerimi
Kerem Can Akkaya
Carsten Pohl
Bertram Schmidt
Peter Neubauer
Fungal Biology and Biotechnology volume 6, Article number: 17 (2019)
https://fungalbiolbiotech.biomedcentral.com/articles/10.1186/s40694-019-0080-y