In this study, the performance characteristics of hemp shives impregnated with linseed oil and tung tree oil (HS)- and corn starch (CS)-based biocomposites containing flame retardants were evaluated before and after treatment with the mixture of bacterium Pseudomonas putida and fungus Rhizopus oryzae. Enzymatic activities and physical-mechanical properties such as water absorption, thickness swelling, compressive strength, and thermal conductivity were tested to evaluate the suitability of selected composites for thermal insulation purposes. In addition, electron microscopy was used to investigate the impact of microorganisms on the microstructure of the material. It was determined that the type of oil used for impregnation significantly affects the properties of biocomposites after 6 months of incubation with mixture of bacterium P. putida and fungus Rh. oryzae. Biocomposites impregnated with linseed oil and after treatment with a mixture of microorganisms had cellulase activity of 25 U/mL, endo β-1-4-glucanase activity of 26 U/mL, lipase activity of 101 U/mL, only a 10% decrease in compressive strength, 50% higher short-term water absorption, unchanged swelling in thickness, and slightly decreased thermal conductivity compared to control biocomposites. At the same time, biocomposites with tung tree oil had a much more pronounced deterioration of the properties tested, cellulase activity of 28 U/mL, endo β-1-4-glucanase activity of 37 U/mL, lipase activity of 91 U/mL, two times lower compressive strength and two times higher short-term water absorption, 2.5 times greater thickness swelling, and a slightly increased thermal conductivity. We conclude that linseed oil provides better protection against the action of microorganisms compared to impregnation with tung tree oil.

In the present work, the low-temperature synthesis of substituted calcium hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, HAP) with copper and zinc ions on titanium substrates was performed. Initially, CaCO₃ coatings were synthesised on titanium substrate using the sol-gel method at 550 °C in a CO₂ atmosphere. Crystalline calcium hydroxyapatite was then synthesised from these CaCO₃ coatings through the dissolution-precipitation method at low temperature (80 °C). X-ray diffraction (XRD) analysis, FTIR and Raman spectroscopies, and scanning electron microscopy (SEM) were employed to evaluate the phase composition, surface functional groups, crystallinity, and morphology of the coatings. The results showed the formation of hexagonal HAP particles with a size of 20 nm at low temperature, exhibiting high homogeneity in particle size distribution. In the calcium hydroxyapatite, some of the Ca²⁺ ions were replaced by Cu²⁺ ions. Heating the mixture of Ca(NO₃)₂ and Cu(NO₃)₂ solutions at 550 °C in a CO₂ atmosphere led to the formation of copper hydroxide carbonate (malachite, Cu₂(OH)₂CO₃) along with CaCO₃. The reaction between the sol-gel precursor obtained and Na₂HPO₄ resulted in the formation of copper-substituted hydroxyapatite (Cu-HAP). Different synthesis methods were tested with Zn²⁺ ions, and on the surface of the coating, Zn(OH)(NO₃)(H₂O), Zn₃(OH)₄(NO₃)₂, and unreacted CaCO₃ were formed. Antibacterial properties of the coatings were tested using the inhibition zone method. No inhibition zones were observed for HAP. However, in the Cu and Zn containing coatings, inhibition zones were observed in the presence of a colony of B. subtilis bacteria. However, no inhibition zones were detected in the presence of E. coli bacteria.

Biocomposite boards (BcBs) composed of hemp shives and corn starch are known as thermal insulating or structural building materials. Therefore, they must be stable during exploitation. However, BcBs are exposed to microorganisms present in the environment, and it is of great interest to investigate the biodegradation behaviour of these materials. This work identified microorganisms growing on BcBs that contain either Flovan CGN or expandable graphite as flame retardants and selected fungi such as Rhizopus oryzae and Aspergillus fumigatus to test the way they affect the materials of interest. For this purpose, the enzymatic activity of cellulases and amylases produced by these organisms were determined. In addition, the apparent density as well as compressive strength of the affected boards were evaluated. The results showed that apparent density and compressive strength deteriorated in BcB composition with the Flovan CGN flame retardant. At the same time, the level of deterioration was lower when the expandable graphite was used, suggesting that it also acts as an antimicrobial agent. A scanning electronic microscopy analysis was employed to monitor the growth of microorganisms in the BcBs. Such analysis demonstrated that, regardless of BcB composition, fungi easily penetrate into the middle layers of the material.

This study is carried out in order to review the deformation properties, strength, applications and suitability of polyurethane resin as a ground improvement method applied for bridge abutment construction. Since it is applied in the ground, awareness on polyurethane degradation needs to be emphasised. Deformation properties were determined for resin injections before and after degradation. The degradation of samples was studied by exposure to gasoline, diesel, oil, NaCl salt solutions with different concentrations (59, 193 and 301 kg/m3) and a mixture of fungi. After the degradation tests, compressibility tests were also performed. The use of resin as a ground improvement method has several advantages over conventional methods. The information presented enables road and bridges engineers and construction professionals to make competent decisions about implementing this innovative technique in the projects.

The use of microalgae as a raw material for biogas production is promising. Macroalgae were mixed with cattle manure, wheat straw, and an inoculant from sewage sludge. Mixing macroalgae with co-substrates increased biogas and methane yield. The research was carried out using a three-stage bioreactor. During biogas production, the dynamics of the composition of the microbiota in the anaerobic chamber of the bioreactor was evaluated. The microbiota composition at different organic load rates (OLRs) of the bioreactor was evaluated. This study also demonstrated that in a three-stage bioreactor, a higher yield of methane in biogas was obtained compared to a single-stage bioreactor. It was found that the most active functional pathway of methane biosynthesis is PWY-6969, which proceeds via the TCA cycle V (2-oxoglutarate synthase). Microbiota composition and methane yield depended on added volatile solids (VS_added). During the research, it was found that after reducing the ORL from 2.44 to 1.09 kg VS/d, the methane yield increased from 175.2 L CH₄/kg VS_added to 323.5 L CH₄/kg VS_added.

Clay materials were prepared with clay and sapropel (SP) or clay and modified (frozen) sapropel (FSP) as the main raw materials. Clay-based materials were formed by mixing clay with a different dosage of SP or FSP (5–30 wt.%). The effect of SP or FSP on the properties and biological resistance of clay-based materials was studied. The results show that the bulk density of clay-based materials decreased, and the compressive strength and initial rate of water absorption increased with the increase in the SP or FSP amount in the clay mixture. Research has shown that SP or FSP can be added as a natural additive containing microfibers to improve the mechanical properties of clay materials. When clay bricks had less than 15% sapropel, dry or frozen, we tested the resistance impact of the fungi Rhodotorula mucilaginosa, Stachybotrys chartarum, Cladosporium cladosporioides, and Aureobasidium pullulans under normal conditions.