The present study aimed to identify the effect of heavy metal concentration and soil pH on the abundance of the selected soil microorganisms within ArcelorMittal Poland steelworks, Cracow. The analysis included 20 soil samples, where the concentration of Fe, Zn, Cd, Pb, Ni, Cu, Mn, Cr and soil pH were evaluated together with the number of mesophilic bacteria, fungi, Actinomycetes and Azotobacter spp. In the majority of samples soil pH was alkaline. The limits of heavy metals exceeded in eight samples and in one sample, the concentration of Zn exceeded 31-fold. Chromium was the element which most significantly limited the number of bacteria and Actinomycetes.

The problem of cleaning and disinfecting surfaces has become extremely important in the context of the ongoing SARS-CoV-2 coronavirus pandemic. However, it should be considered that, in everyday life, we come into contact with many other viruses, as well as pathogenic bacteria and fungi, that may cause infections and diseases. Hence, there is a continuous need to search for new and more effective methods of fighting pathogens. Due to their documented antimicrobial activity, silver nanoparticles may be an interesting alternative to the commonly used surface cleaners and disinfectants. Therefore, the present study aimed to evaluate the bactericidal properties of silver nanoparticles obtained with the use of nontoxic plant waste biomass against bacteria isolated from the environment. Silver nanoparticles with the desired physicochemical characteristics were obtained by a simple and rapid chemical reduction method using plant waste such as unused parsley stems and potato peels (the biogenic method). A nanosilver colloid was also prepared by the chemical reduction method, but with reducing and stabilizing chemical substances (the chemical method) used as a control. The bacterial susceptibility to nanosilver synthesized using both methods was evaluated using the disk-diffusion method. The sensitivity of particular Escherichia coli and Staphylococcus aureus isolates to nanosilver varied considerably, and the strongest antimicrobial effect was found in the case of nanoparticles synthesized by the chemical method using a strong chemical reducing agent and a polymeric stabilizing substance, while nanosilver obtained using the biogenic method, using phytochemicals, also had a strong antimicrobial effect, which was found to be extremely satisfactory. Thus, it can be strongly concluded that the biogenic, pro-ecological method of synthesis with the use of plant waste biomass presented in this work allows the application of biogenic nanosilver as a component of agents for washing and disinfection of public utility surfaces.

New ways of managing hop sediments from brewing and fermentation of beer are constantly being sought and the existing ones improved as part of the circular economy. These wastes are not generated in large amounts, but the absence of their proper characteristics may lead to further processing errors. The study analyses the composting of hop waste under laboratory conditions and the effects of the biological activity of composts introduced into the soil. The study was carried out on two-hop sediments from two different technological stages of beer production: hot trub (HT) and spent hops (SH). Chemical, microbiological and biochemical analyses, as well as the assessment of phytotoxicity to Lepidium sativum L., were performed in the materials. The results proved that, due to their formation technology, the tested feedstocks are safe from an epidemiological point of view and are not a source of microbial contamination. Inhibitory properties for plant development were found for HT and it most likely results from the organic compound content. The mineral composition of hot trub does not exclude composting if its share in biomass is low. Spent hops (SH) were characterised by a significant total nitrogen content, which affected the composting process. Composting this sediment required the selection of substrates with a wide C:N ratio. The number of microorganisms inhabiting the analysed material was very diverse and varied depending on the type of sediments. The sample that contained the composted SH from dry hopping had a much larger number of microorganisms than the sample with HT from wet hopping.

The aim of this research was to evaluate exposure to microbiological aerosol of persons staying in selected office and teaching areas of the university premises. The number and biodiversity of microorganisms constituting the bioaerosol, in particular the Staphylococcus spp., and their drug resistance profile, were determined. Moreover, the influence of temperature, level of airborne particle concentration and the type of ventilation on the number of microorganisms was analysed. The monitoring was carried out using the MAS-100 impactor. The level of airborne particle concentration was measured using the DustTrak II dust meter. The analysis of drug resistance level of staphylococci was carried out using the disk-diffusion method. On the basis of research conducted, the highest microbiological air contamination was found in the biomass lab, due to the research carried out there. On the other hand, no unequivocal link between the concentration of microorganisms present in the air and the type of ventilation used was found. Airborne particles concentrations of PM₁₀ and PM_2.5 exceeded the standard limit values – therefore the air was classified as contaminated. In the sampled air, multi-resistant staphylococci were found, which may pose an epidemiological threat to persons staying in the analysed premises.