Ilze Irbe

Chitosan is a well-known heavy metal biosorbent and was incorporated into birch sanding dust mycelium bio-composites (MBs). The chitosan-hybridized MBs with different chitosan contents were characterized by microscopy, porous structure analyses (specific surface area and total pore volume), pH_pzc, functional group content, and FTIR. Microscopy did not reveal any antifungal effect of chitosan on Trametes versicolor. The porous structure of the MBs decreased after hybridization with chitosan. The FTIR spectra and functional group analyses confirmed the presence of chitosan amino groups in the MBs. The chitosan-hybridized MBs were subjected to the adsorption of heavy metals, namely Cu(II) and Cd(II), and the removal percentage and adsorption isotherms were evaluated. Adsorption isotherms were analyzed using the Freundlich and Langmuir models. The results showed a significant increase in the maximum monolayer adsorption capacity for Cu(II), calculated using the Langmuir equation, from <2 mg/g for raw BSD and basic MB without chitosan to 19 mg/g for the MB with 15% chitosan. In the case of Cd(II), no significant increase in adsorption capacity was observed. These findings indicate that hybridization of MBs with chitosan is a promising approach to improve the Cu(II) adsorption capacity of MBs.

The wood of Scots pine (Pinus sylvestris), silver birch (Betula pendula), and European aspen (Populus tremula) was thermally modified in nitrogen under pressure. Three commercial linseed oil-based coatings without or with brown and grey pigments were applied to the specimens. Specimens were placed outside, and weathering stability was assessed for 3 months. The test measured total surface colour change (ΔE) and colonization by wood dicolouring fungi. Following the test, all uncoated specimens demonstrated poor colour fastness and resistance to fungal growth. All tested coatings were unsuitable for protecting untreated wood from dicolouring fungi. The transparent coating was inefficient since it did not significantly prevent untreated or TM wood from fading, and fungal resistance was increased only for a few TM regimes. The colour fastness of specimens with pigmented coatings was enhanced. Specimens with a grey coating exhibited the lowest ΔE and remained consistent throughout the test period. TM specimens with coloured surfaces exhibited greater fungal resistance. However, not all TM aspen and birch regimes had a sufficient growth mark (rating 0 or 1). TM aspen was less resistant to fungi, whereas TM pine displayed very strong fungal resistance across all TM regimes.

Growing environmental concerns and the need for sustainable alternatives to synthetic materials have led to increased interest in bio-based composites. This study investigates the development and characterization of sustainable egg packaging waste (EPW) biocomposites derived from recycled wood fibers and fungal mycelium filaments as a natural binder. Three formulations were prepared using EPW as the primary substrate, with and without the addition of hemp shives and sawdust as co-substrates. The composites were evaluated for granulometry, density, mechanical strength, hygroscopic behavior, thermal conductivity, and fire performance using cone calorimetry. Biocomposites, composed exclusively of egg packaging waste, exhibited favorable fire resistance, lower total heat release (THR) and total smoke release (TSR), extended time to ignition (TTI), reduced hygroscopicity, and higher flexural strength. Biocomposites, containing hemp shives, demonstrated improved compressive strength and thermal insulation but showed weaker fire resistance. Biocomposites, incorporating sawdust, showed intermediate properties with the longest flameout time (TTF) and highest heat release values. Overall, the results demonstrate that EPW-based biocomposites can be tailored through substrate composition to achieve desirable combinations of mechanical, thermal, and fire-retardant properties, highlighting their potential as sustainable alternatives to conventional synthetic materials in building and packaging applications.

In this study, different combinations of mycelium biocomposites (MBs) were developed using primary substrates sourced from the local agricultural, wood processing, and paper industries. The physicomechanical properties, thermal conductivity, and fire behavior were evaluated. The highest bending strength was achieved in composites containing waste fibers and birch sanding dust, with a strength competitive with that of synthetic polymers like EPS and XPS, as well as some commercial building materials. The lowest thermal conductivity was observed in hemp-based MB, with a lambda coefficient of 40 m·W·m⁻¹·K⁻¹, making these composites competitive with non-mycelium insulation materials, including synthetic polymers such as EPS and XPS. Additionally, MB exhibited superior fire resistance compared to various synthetic foams and composite materials. They showed lower peak heat release rates (134–243 k·W·m⁻²) and total smoke release (7–281 m²·m⁻²) than synthetic polymers, and lower total heat release (6–62 k·W·m⁻²) compared to certain wood composites. Overall, the mechanical and thermal properties, along with the fire performance of MB, support their potential as a sustainable alternative to petroleum-based and traditional composite materials in the building industry.

There is insufficient data regarding the biodegradation of wood-based composites (WBC) by wood decay fungi. This study aimed to evaluate the biological durability and water-related properties of different WBC types. Although WBC are primarily designe...

The demand for eco-friendly packaging materials has urged researchers to look for alternatives to petroleum-based polymers. In this regard, paper-based products have turned out to be a promising choice; however, their weak resistance to water has limited their application. The use of various additives to enhance paper’s moisture resistance is a common practice. However, considering the growing global agenda for sustainable development, the search for new bio-based paper additives has become increasingly important. This study investigated the potential synergistic impact of the addition of nanofibrillated cellulose (NFC) and chitosan additives (CHIT) to different fiber combinations to improve paper’s properties, in particular, their wet strength. The efficacy of the additive application order was examined and was found to be crucial in achieving the desired outcomes. The results showed that incorporating CHIT after NFC enhanced the paper’s tensile and burst indicators, as well as the paper stretch in the dry state, by 35–70%, 35–55%, and 20–35%, respectively. In addition, the tensile index and stretch in the wet state improved 9–13 times and 2.5–5.5 times over, respectively. The air permeability decreased 2.5–12 times over. These findings demonstrate that the sequential addition of the NFC and CHIT additives yield a greater enhancement of paper’s properties than using each additive separately.

A significant increase in the consumption of recycled fiber products has been observed worldwide, and the industry is forced to solve the challenges of recycled fiber quality and add strength agents and/or virgin fibers to reach sufficient properties. In order to investigate whether the mechanical and air permeability properties of waste fiber (WF) material can be significantly improved by adding wood kraft fibers (KF), hemp soda fibers (HF), and ammonium persulfate oxidated cellulose nanofibrils (CNF), different fiber blends were prepared and tested. Results revealed the excellence of hemp fibers over wood fibers regarding the improvement of WF products. The results of WF after the addition of 10% mixed fibers (KF + HF) were higher than the results of a 50% KF addition. The impact of CNF depended on fiber composition and properties. A formula for modeling the CNF impact on different fiber compositions was proposed. Obtained fiber material samples showed suitability for home composting, thus contributing to the goals of the European Green Deal regarding reducing landfill waste and the development of cleaner products.

This study investigates the mycelial biomass production and chitosan extraction potential of various Basidiomycota strains, including Heterobasidion annosum, Phanerochaete chrysosporium, Pleurotus ostreatus, Trametes versicolor, and Lentinus lepideus. Both submerged fermentation (SF) and solid-state fermentation (SSF) methods were employed. The chitosan yield in basidiocarps of Pleurotus ostreatus, Agaricus bisporus, and Ganoderma applanatum was also evaluated as a reference material. The chitosan extracted from fungal cells was characterized using elemental analyses and FTIR spectroscopy. Among the cultivated strains, P. chrysosporium exhibited the highest mycelial biomass concentration in SF (1.03 g 100 mL^–1) after 14 days, while T. versicolor achieved the highest biomass concentration in SSF (3.65 g 100 mL^–1). The highest chitosan yield was obtained from the mycelium of P. chrysosporium (0.38%) and T. versicolor (0.37%) in shaken SF. Additionally, commercially cultivated A. bisporus demonstrated the highest chitosan yield in fungal fruiting bodies (1.7%). The extracted chitosan holds potential as a functional biopolymer additive for eco-friendly materials, serving as an alternative to synthetic wet and dry strength agents in packaging materials.

The isolation and potential applications of chitosan from the fungal source is an alternative to crustacean chitosan and synthetic polymers. The strains of Basidiomycota (Heterobasidion annosum, Phanerochaete chrysosporium, Pleurotus ostreatus, Trametes versicolor, Lentinus lepideus) with different environmental distribution, ecological importance, and industrial application were studied for mycelial biomass production in submerged (SF) and solid state fermentation (SSF). Further, the chitosan from fungal cells was extracted and characterized by elemental analyses (nitrogen) and FTIR spectroscopy. The fruiting bodies of Pleurotus ostreatus, Agaricus bisporus and Ganoderma ap-planatum were chosen as a reference material of chitosan content in basidiocarps. Stationary SF gave the lowest biomass yield in comparison with shaken SF and SSF. The role of aeration and agitation in biomass production was clearly observed in shaken SF with the highest yield achieved by P. chrysosporium. The highest biomass yield in SSF produced P. ostreatus and T. versi-color. The content of chitosan within fungal species varied depending on the method of cultiva-tion. The highest chitosan yield among the cultivated strains was obtained from mycelium of P. chrysosporium and T. versicolor in SF. The highest chitosan yield in fungal fruiting bodies demon-strated commercially cultivated mushroom A. bisporus. The extracted chitosan is proposed as functional biopolymer additive for ecological materials to substitute the synthetic wet and dry strength agents in packaging materials.