Periodic Reporting for period 1 - MyBond (Mycelium Material Bonding: Molecular Mechanism and Enhancement Strategy)
Période du rapport: 2024-09-01 au 2026-08-31
The European Green Deal emphasizes the urgency to reduce greenhouse gas emissions and achieve carbon neutrality by transitioning toward sustainable and bio-based materials. Fungal mycelium emerges as a particularly promising material, offering significant environmental advantages due to its biodegradability and its potential to replace petroleum-derived adhesives commonly used in lignocellulosic composites.
Despite these advantages, the effective deployment of fungal materials is constrained by a limited understanding of the molecular mechanisms underlying fungal adhesion. In particular, how surface-associated fungal components, such as exopolysaccharides and hydrophobin-like proteins, contribute to fungal adhesion to substrates remains poorly understood. This knowledge gap restricts material design strategies and limits the tuning of fungal adhesion properties for specific applications.
This project was designed to address these fundamental questions through a targeted investigation of Schizophyllum commune strains, including both wild-type and hydrophobin- (SC3) and hydrophobin-like (SC15) deficient mutants. The goal was to systematically compare fungal adhesion behavior, material morphology, and biochemical composition under different culture conditions. A specific focus was also placed on how drying and surface chemistry influence fungal attachment to various substrates, ranging from porous to hydrophobic.
By clarifying the role of hydrophobins and exopolysaccharides in adhesion, the project aimed to identify mechanisms that could be used for further materials design. The expected outcome was to generate actionable insights that bridge molecular biology and materials science, paving the way for scalable fungal adhesives and fungal biomaterials with reduced environmental impact. These results contribute directly to EU policy goals by enabling the replacement of non-sustainable materials with safe, bio-derived alternatives in sectors ranging from construction to packaging. The project thus supports both scientific advancement and practical innovation in line with Europe’s transition to a climate-neutral, circular economy.
Despite these advantages, the effective deployment of fungal materials is constrained by a limited understanding of the molecular mechanisms underlying fungal adhesion. In particular, how surface-associated fungal components, such as exopolysaccharides and hydrophobin-like proteins, contribute to fungal adhesion to substrates remains poorly understood. This knowledge gap restricts material design strategies and limits the tuning of fungal adhesion properties for specific applications.
This project was designed to address these fundamental questions through a targeted investigation of Schizophyllum commune strains, including both wild-type and hydrophobin- (SC3) and hydrophobin-like (SC15) deficient mutants. The goal was to systematically compare fungal adhesion behavior, material morphology, and biochemical composition under different culture conditions. A specific focus was also placed on how drying and surface chemistry influence fungal attachment to various substrates, ranging from porous to hydrophobic.
By clarifying the role of hydrophobins and exopolysaccharides in adhesion, the project aimed to identify mechanisms that could be used for further materials design. The expected outcome was to generate actionable insights that bridge molecular biology and materials science, paving the way for scalable fungal adhesives and fungal biomaterials with reduced environmental impact. These results contribute directly to EU policy goals by enabling the replacement of non-sustainable materials with safe, bio-derived alternatives in sectors ranging from construction to packaging. The project thus supports both scientific advancement and practical innovation in line with Europe’s transition to a climate-neutral, circular economy.
The project investigated the influence of SC3 and SC15 gene deletion on fungal growth, extracellular secretion, and adhesion properties using four Schizophyllum commune strains: two wild types (H4-8A and 4-39) and two mutants (4-39ΔSC3 and 4-39ΔSC3ΔSC15). These strains were cultivated under both liquid shaking and agar static conditions on a range of substrates to evaluate differences in biomass morphology, extracellular polysaccharide production (notably schizophyllan), surface attachment, and bonding strength to lignocellulosic substrates.
In liquid cultures, H4-8A produced dense, spherical pellets and secreted the most extracellular material (7.43 g/L), with a high yield of precipitable schizophyllan (3.63 g/L). By contrast, 4-39 formed irregular, star-shaped pellets with limited schizophyllan production (0.27 g/L). The deletion strains, despite retaining the pellet morphology of 4-39, showed a dramatic increase in extracellular material and schizophyllan yield (up to 2.62 g/L), without a reduction in sediment biomass. This demonstrates that hydrophobin deletion enhances extracellular polysaccharide production independently of mycelial growth.
Under static incubation, all strains fully colonized the test substrates (wood, glass, Teflon), but only the wild types developed robust aerial hyphae with superhydrophobic surfaces. The mutant strains produced flatter, hydrophilic vegetative mats with reduced aerial coverage, confirmed by water contact angle analysis.
A surface detachment assay was performed to assess mycelium attachment strength on wood, glass, and Teflon. While wet mycelium detached rapidly from non-porous substrates, dried samples adhered more strongly, with strain- and surface-specific differences. Wild-type strains remained attached at high shaking speeds on Teflon, whereas mutants detached earlier. All strains remained stably attached to wood, indicating strong physical interlocking likely due to substrate porosity.
Adhesion testing revealed strain-specific performance. In liquid cultures, ΔSC3 achieved the highest bonding strength (1.83 MPa), while in static incubation, ΔSC3ΔSC15 performed best (1.82 MPa). These differences are attributed to the altered surface composition and hydrophilic properties of the mutants. Overall, the project demonstrated that fungal adhesion can be modulated through genetic and environmental controls, offering a biologically tunable platform for adhesive development.
In liquid cultures, H4-8A produced dense, spherical pellets and secreted the most extracellular material (7.43 g/L), with a high yield of precipitable schizophyllan (3.63 g/L). By contrast, 4-39 formed irregular, star-shaped pellets with limited schizophyllan production (0.27 g/L). The deletion strains, despite retaining the pellet morphology of 4-39, showed a dramatic increase in extracellular material and schizophyllan yield (up to 2.62 g/L), without a reduction in sediment biomass. This demonstrates that hydrophobin deletion enhances extracellular polysaccharide production independently of mycelial growth.
Under static incubation, all strains fully colonized the test substrates (wood, glass, Teflon), but only the wild types developed robust aerial hyphae with superhydrophobic surfaces. The mutant strains produced flatter, hydrophilic vegetative mats with reduced aerial coverage, confirmed by water contact angle analysis.
A surface detachment assay was performed to assess mycelium attachment strength on wood, glass, and Teflon. While wet mycelium detached rapidly from non-porous substrates, dried samples adhered more strongly, with strain- and surface-specific differences. Wild-type strains remained attached at high shaking speeds on Teflon, whereas mutants detached earlier. All strains remained stably attached to wood, indicating strong physical interlocking likely due to substrate porosity.
Adhesion testing revealed strain-specific performance. In liquid cultures, ΔSC3 achieved the highest bonding strength (1.83 MPa), while in static incubation, ΔSC3ΔSC15 performed best (1.82 MPa). These differences are attributed to the altered surface composition and hydrophilic properties of the mutants. Overall, the project demonstrated that fungal adhesion can be modulated through genetic and environmental controls, offering a biologically tunable platform for adhesive development.
This project extends current knowledge by revealing how specific genetic deletions can enhance the adhesive potential of fungal systems. While Schizophyllum commune has been previously studied for schizophyllan production, this work is the first to show that removal of hydrophobin(-like) genes (SC3, SC15) significantly increases schizophyllan yield without compromising mycelial biomass. This finding challenges assumptions about a fixed biomass-exopolysaccharide trade-off and opens new pathways for strain engineering.
A second advancement lies in demonstrating that vegetative hyphae, not aerial structures, can be more effective for substrate bonding. Wild-type strains formed superhydrophobic aerial hyphae, which in some cases reduced adhesion, while mutants with flatter, hydrophilic mats achieved superior bonding. These results suggest that aerial hyphae may hinder, rather than help, adhesion in some contexts, and that fungal surface properties can be tuned to match material demands.
A third contribution of this work is the development of a scalable method to quantify fungal attachment strength through stepwise agitation. This revealed that drying enhances adhesion, and that wild-type strains exhibit greater attachment to hydrophobic substrates like Teflon, presumably due to hydrophobin-mediated surface interactions. These results provide quantitative evidence supporting fungal application on diverse surface types.
Practically, the study identifies clear opportunities and barriers for commercial adoption. This strength is comparable to commercial glue tested under the same conditions and falls within the range of functional adhesion values reported for biobased adhesives. However, performance comparisons depend strongly on substrate, adhesive spread rate, and pressing conditions. Water retention in liquid-cultured biomass remains a limiting factor for adhesive application, requiring further development of drying or formulation techniques. Conversely, the ability to enhance polysaccharide production through simple gene deletions offers a promising, scalable strategy for increasing adhesive efficiency.
To advance toward industrial uptake, future efforts should focus on: 1) scaling up biomass production and bonding trials under industry-relevant conditions; 2) refining formulations to improve spread ability and consistency; 3) integrating fungal adhesives into existing product testing frameworks; and 4) developing IP and regulatory pathways that support adoption of genetically modified fungal strains in sustainable materials markets. This work establishes a blueprint for bio-based adhesive innovation aligned with the EU’s climate and circular economy targets.
A second advancement lies in demonstrating that vegetative hyphae, not aerial structures, can be more effective for substrate bonding. Wild-type strains formed superhydrophobic aerial hyphae, which in some cases reduced adhesion, while mutants with flatter, hydrophilic mats achieved superior bonding. These results suggest that aerial hyphae may hinder, rather than help, adhesion in some contexts, and that fungal surface properties can be tuned to match material demands.
A third contribution of this work is the development of a scalable method to quantify fungal attachment strength through stepwise agitation. This revealed that drying enhances adhesion, and that wild-type strains exhibit greater attachment to hydrophobic substrates like Teflon, presumably due to hydrophobin-mediated surface interactions. These results provide quantitative evidence supporting fungal application on diverse surface types.
Practically, the study identifies clear opportunities and barriers for commercial adoption. This strength is comparable to commercial glue tested under the same conditions and falls within the range of functional adhesion values reported for biobased adhesives. However, performance comparisons depend strongly on substrate, adhesive spread rate, and pressing conditions. Water retention in liquid-cultured biomass remains a limiting factor for adhesive application, requiring further development of drying or formulation techniques. Conversely, the ability to enhance polysaccharide production through simple gene deletions offers a promising, scalable strategy for increasing adhesive efficiency.
To advance toward industrial uptake, future efforts should focus on: 1) scaling up biomass production and bonding trials under industry-relevant conditions; 2) refining formulations to improve spread ability and consistency; 3) integrating fungal adhesives into existing product testing frameworks; and 4) developing IP and regulatory pathways that support adoption of genetically modified fungal strains in sustainable materials markets. This work establishes a blueprint for bio-based adhesive innovation aligned with the EU’s climate and circular economy targets.