Propose The aim of this study was to investigate the effect of the composting process, conducted with the addition of various substrates, on the biological and ecotoxic properties of composts. Methods Composts were prepared on the basis of plant material amended with biochar, sewage sludge, coffee grounds, or yeast effluent. The composting process was carried out for 140 days. The biological activity of mixtures was determined in the process, while microorganism abundance and ecotoxicity, in the final product. Results The addition of biochar had no significant effect on the rate of the composting process measured by temperature; however, biochar-amended treatments showed a smaller loss of dry matter and higher C:N ratio. Compared to the control, reduced biological activity measured by the germination capacity of seeds was identified in treatments with maize straw composts and composts enriched with coffee grounds and yeast effluent. The inhibitory effect on the germination capacity was alleviated in treatments with biochar. The addition of biochar to compost with sewage sludge decreased the abundance of Escherichia coli and Salmonella ssp. and increased the total number of bacteria and fungi. In the case of composts with coffee grounds, biochar had an opposite effect to that observed for composts with sewage sludge. Conclusions Biochar to sewage sludge and coffee grounds reduced ecotoxicity of composts to test organisms: Vibrio fischeri, Sianpis alba, Triticum L. and Eisenia fetida.

Historical facilities such as churches, crypts, libraries and museums are crucial for preserving cultural heritage but at the same time, they are frequently visited tourist objects and working environment. The aim of this study was to assess whether there are differences in the concentration and size distribution of bacterial and fungal aerosol in the mentioned groups of historical objects in Kraków, as well as to determine if there is tendency for seasonal fluctuations of bioaerosol concentrations, and what environmental parameters affect them most significantly. The concentrations of bacterial and fungal aerosol were measured in ten historical objects—churches, crypts, libraries and museums—using a six-stage Andersen impactor. Microbiological analyses were accompanied by measurements of particulate matter (PM₁₀, PM₄, PM_2.5 and PM₁) and microclimatic parameters. The results showed that the studied objects differ in terms of bioaerosol levels, but the differences were not drastic and in terms of bacterial aerosol concentrations the objects can be arranged as follows: churches > libraries > museums > crypts, while for fungal aerosol the order would be: churches > museums > crypts > libraries. The concentrations of bioaerosol did not exceed the safety levels for human exposure, but the levels suggesting possible threat of biodeterioration and the presence of internal source of contamination were exceeded in nearly all sites. The share of respirable fraction of bioaerosol was high (42.1–90.5% for bacteria and 80.7–94.7% for fungi). Bioaerosol concentration was most significantly associated with indoor temperature, and the impact of particulate matter was only moderate.

Essential oils exhibit strong antimicrobial effects that can serve as a substitute for synthetic pesticides. However, many reports mention the use of essential oils in protecting above-ground plant organs and storing raw materials and seeds, but only a few address the effects of treatments on soil microbiota. Regarding this, it is necessary to find a solution that will prevent the rapid degradation of oils in soil and extend the period of their action on the soil microbiota. The solution to this problem can be microencapsulation, where the choice of carrier plays a key role. In our experiment, maltodextrin was studied, often used in the microencapsulation of essential oils. It was examined independently in two doses (M1 and M2, with 50 and 200 g kg⁻¹, respectively) and a combination with two essential oils known for their antimicrobial activity. We hypothesized that the selected microbial communities would react differently to the stress caused by maltodextrin-encapsulated essential oils. The serial dilution method assessed the number of colony-forming units (CFU) of bacteria, fungi, and actinomycetes. As the goal of microencapsulation was to prolong the effect of essential oils, their reaction was observed over a longer period. The soil microbial populations were examined in sandy and loamy soil at 1, 7, 14, and 78 days after encapsulated essential oils were mixed with the soil samples. In both types of soil, a significant increase in bacteria and actinomycetes was observed with maltodextrin in both doses. Encapsulated peppermint and caraway oils had different effects on microbes, both inhibitory and stimulatory. It is also important to note that peppermint with a smaller dose of maltodextrin significantly inhibited the growth of fungi in sandy soil in all measurements, as well as that caraway oil with a higher dose of maltodextrin significantly stimulated the growth of bacteria and actinomycetes in sandy soil. The higher dose of maltodextrin could explain this stimulation. Further research is recommended to test different doses of essential oils and maltodextrin, which would lead to the optimal dose of both wall and core materials.