Existing research on mycelium-based materials recognizes the binding capacity of fungal hyphae. Fungal hyphae digest and bond to the surface of the substrate, form entangled networks, and enhance the mechanical strength of mycelium-based composites. This investigation was driven by the results of an ongoing project, where we attempt to provide basic concepts for a broad application of a mycelium and chipped wood composite for building components. Simultaneously, we further explore the binding capacity of mycelium and chipped wood composites with a series of experiments involving different mechanical interlocking patterns. Although the matrix material was analyzed on a micro-scale, the samples were developed on a meso-scale to enhance the bonding surface. The meso-scale allows exploring the potential of the bio-based material for use in novel construction systems. The outcome of this study provides a better understanding of the material and geometrical features of mycelium-based building elements.

Natural fibres have a high potential as reinforcement of polymer matrices, as they combine a high specific strength and modulus with sustainable production and reasonable prices. Modifying the fibre surface is a common method to increase the adhesion and thereby enhance the mechanical properties of composites. In this study, a novel sustainable surface treatment is presented: the fungal enzyme laccase was utilised with the aim of covalently binding the coupling agent dopamine to flax fibre surfaces. The goal is to improve the interfacial strength towards an epoxy matrix. SEM and AFM micrographs showed that the modification changes the surface morphology, indicating a deposition of dopamine on the surface. Fibre tensile tests, which were performed to check whether the fibre structure was damaged during the treatment, showed that no decrease in tensile strength or modulus occurred. Single fibre pullout tests showed a 30% increase in interfacial shear strength (IFSS) due to the laccase-mediated bonding of the coupling agent dopamine. These results demonstrate that a laccase + dopamine treatment modifies flax fibres sustainably and increases the interfacial strength towards epoxy.

Hispidin (6-(3,4-dihydroxystyrl)-4-hydroxy-2-pyrone) production in submerged cultured mycelia of the basidiomycete Inonotus hispidus was doubled in shake flasks through irradiation with white light. The daily addition of 1 mM hydrogen peroxide as a chemical stressor and a repeated supplementation of the shake flask cultures with 2 mM caffeic acid, a biogenetic precursor, further increased the hispidin synthesis. These cultivation conditions were combined and applied to parallel fermentation trials on the 4 L scale using a classical stirred tank bioreactor and a wave bag bioreactor. No significant differences in biomass yield and colorant production were observed. The hispidin concentration in both bioreactors reached 5.5 g·L⁻¹, the highest ever published. Textile dyeing with hispidin was successful, but impeded by its limited light stability in comparison to industrial dyes. However, following the idea of sustainability and the flawless toxicity profile, applications in natural cosmetics, other daily implements, or even therapeutics appear promising.

The blue-green pigment xylindein, produced by the soft rot fungus Chlorociboria aeruginascens, is of considerable interest for various applications such as the veneer industry or organic semiconductors. The studies presented were performed in order to understand the fungal growth as well as the pigment production of C. aeruginascens. Therefore, various nutrient compositions were investigated. As a result, observations of the formation of xylindein through C. aeruginascens decoupling from growth were made. In the primary metabolism the uncolored biomass is formed. Various carbohydrates were determined as nutrients for the fungus and as a nitrogen source it was observed that the fungus prefers the complex organic nitrogen source, that being yeast extract. Furthermore, it was discovered that the ratio between carbohydrate and nitrogen sources encourages the switch of the metabolism and therewith the production of the blue-green pigment xylindein.

Application of lipases (preferentially Candida antarctica Lipase B, CALB) for melt polycondensation of aliphatic polyesters by transesterification of activated dicarboxylic acids with diols allows to displace toxic metal and metal oxide catalysts. Immobilization of the enzyme enhances the activity and the temperature range of use. The possibility to use enzyme-catalyzed polycondensation in melt is studied and compared to results of polycondensations in solution. The experiments show that CALB successfully catalyzes polycondensation of both, divinyladipate and dimethylsuccinate, respectively, with 1,4-butanediol. NMR spectroscopy, relative molar masses obtained by size exclusion chromatography, MALDI-TOF MS and wide-angle X-ray scattering are employed to compare the influence of synthesis conditions for poly(butylene adipate) (PBA) and poly(butylene succinate) (PBS). It is shown that the enzymatic activity of immobilized CALB deviates and influences the molar mass. CALB-catalyzed polycondensation of PBA in solution for 24 h at 70 °C achieves molar masses of up to M_w~60,000 g/mol, higher than reported previously and comparable to conventional PBA, while melt polycondensation resulted in a moderate decrease of molar mass to M_w~31,000. Enzymatically catalyzed melt polycondensation of PBS yields M_w~23,400 g/mol vs. M_w~40,000 g/mol with titanium(IV)n-butoxide. Melt polycondensation with enzyme catalysis allows to reduce the reaction time from days to 3–4 h.

The soft rot fungus Chlorociboria aeruginascens produces a blue–green pigment xylindein, which is of considerable interest for various applications such as in the veneer industry or in organic semiconductors. To understand the fungal growth as well as pigment production of C. aeruginascens, several studies were performed, the results of which are presented here. These studies investigated various growth conditions such as temperature, pH value, oxygen level and light intensity. It was observed that the formation of xylindein by C. aeruginascens decoupled from growth. In the primary metabolismus, the uncolored biomass is formed. Pigment production took place within the secondary metabolism, while biomass growth as well as pigment production depended on various growth conditions. It was also found that certain conditions encourage the switch in metabolism, leading to pigment production.