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Mycelium-based materials derived from white-rot fungi have attracted increasing attention as sustainable and eco-friendly alternatives to conventional products. However, their mechanical strength and durability remain relatively inferior. Molecular breeding of white-rot fungi offers a promising strategy to address these limitations. Recent studies have suggested that mycelial density and cell wall structure play key roles in determining the physical properties of mycelium-based materials. In this study, we disrupted mbp1 , which encodes a transcription factor required for normal mycelial growth and cell wall synthesis, in the white-rot fungus Pleurotus ostreatus and investigated the effects on mycelium mats and mycelium-based composites. The mycelium mats of the dikaryotic mbp1 disruptants exhibited higher Young’s moduli and ultimate tensile strengths than those of the control strain (20b×#61), indicating that mbp1 disruption resulted in stiffer mycelium mats. This may be because of the increased mycelial density in the dikaryotic mbp1 disruptants. In addition, the dikaryotic mbp1 disruptants produced harder mycelium-based composites than the strain 20b×#61. These findings indicate that mbp1 disruption improved the characteristics of mycelium-based composites. To our knowledge, this is the first study demonstrating that molecular breeding can enhance the performance of mycelium-based composites, thereby paving the way for the development of efficient strategies to advance mycelium-based materials. Key points • mbp1 disruption resulted in stiffer mycelium mats. • Dikaryotic mbp1 disruptants formed thinner but denser mycelium mats. • mbp1 disruption improved the mechanical strength of mycelium-based composites.

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.

Background Mushroom showed pellet, clump and/or filamentous mycelial morphologies during submerged fermentation. Addition of microparticles including Talc (magnesium silicate), aluminum oxide and titanium oxide could control mycelial morphologies to improve mycelia growth and secondary metabolites production. Here, effect of microparticle Talc (45 μm) addition on the mycelial morphology, fermentation performance, monosaccharide compositions of polysaccharides and enzymes activities associated with polysaccharide synthesis in G. frondosa was well investigated to find a clue of the relationship between polysaccharide biosynthesis and morphological changes. Results Addition of Talc decreased the diameter of the pellets and increased the percentage of S-fraction mycelia. Talc gave the maximum mycelial biomass of 19.25 g/L and exo-polysaccharide of 3.12 g/L at 6.0 g/L of Talc, and mycelial polysaccharide of 0.24 g/g at 3.0 g/L of Talc. Talc altered the monosaccharide compositions/percentages in G. frondosa mycelial polysaccharide with highest mannose percentage of 62.76 % and lowest glucose percentage of 15.22 % followed with the corresponding changes of polysaccharide-synthesis associated enzymes including lowest UDP-glucose pyrophosphorylase (UGP) activity of 91.18 mU/mg and highest UDP-glucose dehydrogenase (UGDG) and GDP-mannose pyrophosphorylase (GMPPB) activities of 81.45 mU/mg and 93.15 mU/mg. Conclusion Our findings revealed that the presence of Talc significantly changed the polysaccharide production and sugar compositions/percentages in mycelial and exo-polysaccharides by affecting mycelial morphology and polysaccharide-biosynthesis related enzymes activities of G. frondosa .

2-Phenylethanol (2-PE) is an aromatic compound with a rose-like fragrance that is widely used in food and other industries. Yeasts have been implicated in the biosynthesis of 2-PE; however, few studies have reported the involvement of filamentous fungi. In this study, 2-PE was detected in Annulohypoxylon stygium mycelia grown in both potato dextrose broth (PDB) and sawdust medium. Among the 27 A. stygium strains investigated in this study, the strain “Jinjiling” (strain S20) showed the highest production of 2-PE. Under optimal culture conditions, the concentration of 2-PE was 2.33 g/L. Each of the key genes in Saccharomyces cerevisiae shikimate and Ehrlich pathways was found to have homologous genes in A. stygium . Upon the addition of L-phenylalanine to the medium, there was an upregulation of all key genes in the Ehrlich pathway of A. stygium , which was consistent with that of S. cerevisiae . A. stygium as an associated fungus provides nutrition for the growth of Tremella fuciformis and most spent composts of T. fuciformis contain pure A. stygium mycelium. Our study on the high-efficiency biosynthesis of 2-PE in A. stygium offers a sustainable solution by utilizing the spent compost of T. fuciformis and provides an alternative option for the production of natural 2-PE. Key points • Annulohypoxylon stygium can produce high concentration of 2-phenylethanol. • The pathways of 2-PE biosynthesis in Annulohypoxylon stygium were analyzed. • Spent compost of Tremella fuciformis is a potential source for 2-phenylethanol.

Turnover of fungal biomass in forest litter and soil represents an important process in the environment. To date, knowledge of mycelial decomposition has been derived primarily from short-term studies, and the guild of mycelium decomposers has been poorly defined. Here, we followed the fate of the fruiting bodies of an ectomycorrhizal fungus in litter and soil of a temperate forest over 21 wk. The community of associated microbes and enzymatic processes in this specific substrate were described. The decomposition of fungal fruiting bodies exhibited biphasic kinetics. The rapid initial phase, which included the disappearance of DNA, was followed by a slower turnover of the recalcitrant fraction. Compared with the surrounding litter and soil, the mycelium represented a hotspot of activity of several biopolymer-degrading enzymes and high bacterial biomass. Specific communities of bacteria and fungi were associated with decomposing mycelium. These communities differed between the initial and late phases of decomposition. The bacterial community associated with decomposing mycelia typically contained the genera Pedobacter, Pseudomonas, Variovorax, Chitinophaga, Ewingella and Stenotrophomonas, whereas the fungi were mostly nonbasidiomycetous r-strategists of the genera Aspergillus, Penicillium, Mortierella, Cladosporium and several others. Decomposing ectomycorrhizal fungal mycelium exhibits high rates of decomposition and represents a specific habitat supporting a specific microbial community.

In boreal forest soils, ectomycorrhizal fungi are fundamentally important for carbon (C) dynamics and nutrient cycling. Although their extraradical mycelium (ERM) is pivotal for processes such as soil organic matter build-up and nitrogen cycling, very little is known about its dynamics and regulation. In this study, we quantified ERM production and turnover, and examined how these two processes together regulated standing ERM biomass in seven sites forming a chronosequence of 12- to 100-yr-old managed Pinus sylvestris forests. This was done by determining ERM biomass, using ergosterol as a proxy, in sequentially harvested in-growth mesh bags and by applying mathematical models. Although ERM production declined with increasing forest age from 1.2 to 0.5 kg ha−1 d−1, the standing biomass increased from 50 to 112 kg ha−1. This was explained by a drastic decline in mycelial turnover from seven times to one time per year with increasing forest age, corresponding to mean residence times from 25 d up to 1 yr. Our results demonstrate that ERM turnover is the main factor regulating biomass across differently aged forest stands. Explicit inclusion of ERM parameters in forest ecosystem C models may significantly improve their capacity to predict responses of mycorrhiza-mediated processes to management and environmental changes.

Fungi produce numerous low molecular weight molecules endowed with a multitude of biological activities. However, mining the full-genome sequences of fungi indicates that their potential to produce secondary metabolites is greatly underestimated. Because most of the biosynthesis gene clusters are silent under laboratory conditions, one of the major challenges is to understand the physiological conditions under which these genes are activated. Thus, we cocultivated the important model fungus Aspergillus nidulans with a collection of 58 soil-dwelling actinomycetes. By microarray analyses of both Aspergillus secondary metabolism and full-genome arrays and Northern blot and quantitative RT-PCR analyses, we demonstrate at the molecular level that a distinct fungal-bacterial interaction leads to the specific activation of fungal secondary metabolism genes. Most surprisingly, dialysis experiments and electron microscopy indicated that an intimate physical interaction of the bacterial and fungal mycelia is required to elicit the specific response. Gene knockout experiments provided evidence that one induced gene cluster codes for the long-sought after polyketide synthase (PKS) required for the biosynthesis of the archetypal polyketide orsellinic acid, the typical lichen metabolite lecanoric acid, and the cathepsin K inhibitors F-9775A and F-9775B. A phylogenetic analysis demonstrates that orthologs of this PKS are widespread in nature in all major fungal groups, including mycobionts of lichens. These results provide evidence of specific interaction among microorganisms belonging to different domains and support the hypothesis that not only diffusible signals but intimate physical interactions contribute to the communication among microorganisms and induction of otherwise silent biosynthesis genes.

This study investigates, for the first time, the relationship between carbon (δ13C) and nitrogen stable isotopic composition of Aspergillus niger mycelium, used as chitin and chitosan sources, and the fungus diet under controlled cultivation conditions. Four diets were tested, combining different carbon (C3- and C4-glucose) and nitrogen sources (KNO3 and NH4Cl). Results showed that carbon sources significantly influenced δ13C values of the mycelium: C4-glucose diets led to more negative Δ13C values (δ13CMYCELIUM-δ13CDIET) compared to C3-glucose diets. Nitrogen sources also affected isotopic fractionation, with KNO3 leading to negative Δ15N (δ15NMYCELIUM-δ15NDIET) and NH4Cl yielding positive Δ15N. Conversely, pH and temperature showed negligible effects on δ15N, while continuous aeration during growth significantly decreased δ15N, possibly due to partial assimilation of atmospheric nitrogen. These findings demonstrate that both nutrient and cultivation parameters can modulate the isotopic fractionation in A. niger, particularly for nitrogen. Although a direct correlation between diet composition and δ15N could not be established, this work provides the first experimental link between fungal metabolism and its isotopic fingerprint. The results offer a scientific foundation for applying stable isotope ratio analysis to authenticate and trace fungal-derived chitin and chitosan, with potential applications in food and winemaking industries.

UV and gamma irradiation mutagenesis was applied on Aspergillus fumigatus and Alternaria tenuissima in order to improve their producing ability of paclitaxel. Among the screened mutants, two stable strains (designated TXD105–GM6 and TER995–GM3) showed the maximum paclitaxel production. Paclitaxel titers of the two respective mutants were dramatically intensified to 1.22- and 1.24-fold, as compared by their respective parents. Immobilization using five different entrapment carriers of calcium alginate, agar-agar, Na-CMC, gelatin, and Arabic gum was successfully applied for production enhancement of paclitaxel by the two mutants. The immobilized cultures were superior to free-cell cultures and paclitaxel production by the immobilized mycelia was much higher than that of the immobilized spores using all the tried carriers. Moreover, calcium alginate gel beads were found the most conductive and proper entrapment carrier for maximum production of paclitaxel. The feasibility of the paclitaxel production by the immobilized mycelia as affected by incubation period, medium volume, and number of beads per flask was adopted. Under the favorable immobilization conditions, the paclitaxel titers were significantly intensified to 1.31- and 1.88-fold by the respective mutants, as compared by their free cultures. The obtained paclitaxel titers by the immobilized mycelia of the respective mutants (694.67 and 388.65 μg L −1 ) were found promising in terms of fungal production of paclitaxel. Hence, these findings indicate the future possibility to reduce the cost of producing paclitaxel and suggest application of the immobilization technique for the biotechnological production of paclitaxel at an industrial scale.

The mycelia of Hericium erinaceus contain neuroprotective cyathane diterpenoids (e.g., erinacine A). There is evidence that cultivation of submerged mycelia with surfactants increases glucose uptake and biomass, but the impact on erinacine production is unknown. Here, we tested the impact of glucose and polysorbate 80 on the mycelial erinacine profiles of five Hericium strains cultivated under submergence, including those of Hericium erinaceus, Hericium americanum, and Hericium coralloides. Metabolite profiling confirmed that mycelial extracts contained 13% to 91% of the erinacines A, C and P in additive-free cultures of all strains, with the remainder secreted to the culture medium. Overall, erinacine P production was several orders of magnitude greater than that of the other erinacines, except for H. erinaceus (DAOMC 251029), where erinacine C was most evident. H. coralloides (DAOMC 251017) produced the greatest concentrations of erinacines A and P. For the most part mycelial erinacine concentrations were reduced in cultures co-supplemented with glucose and polysorbate 80. This treatment caused an 83–100% reduction in the concentrations of erinacines A, C, and P in the mycelial extracts of most strains. By contrast, there was evidence that glucose and polysorbate 80 had no effect on erinacine A production within mycelia of H. americanum, and erinacine P concentrations in H. erinaceus (DAOMC 251029) and H. americanum (DAOMC 251011). In most strains, the secretion of erinacines to the culture medium declined with glucose and polysorbate 80. Conversely, these additives increased the concentrations of erinacines C and P in the culture medium filtrate of H. americanum (DAOMC 21467) and yielded more secreted erinacine P in H. erinaceus (DAOMC 251029). The information provides feasible strategies to produce mycelia with unique erinacine profiles including those rich in erinacine P.