Biofilm formation by selected microbial strains isolated from wastewater and their consortia: mercury resistance and removal potential.

Wastewater often contains an increased amount of mercury and, at the same time, resistant microorganisms. During wastewater treatment, a biofilm of indigenous microorganisms is often unavoidable. Therefore, the objective of this research is to isolate and identify microorganisms from wastewater and investigate their ability to form biofilms for possible application in mercury removal processes. The resistance of planktonic cells and their biofilms to the effects of mercury was investigated using Minimum Biofilm Eradication Concentration-High Throughput Plates. The formation of biofilms and the degree of resistance to mercury were confirmed in polystyrene microtiter plates with 96 wells. Biofilm on AMB Media carriers (Assisting Moving Bad Media) was quantified using the Bradford protein assay. The removal of mercury ions by biofilms formed on AMB Media carriers of selected isolates and their consortia was determined by a removal test in Erlenmeyer flasks simulating MBBR. All isolates in planktonic form showed some degree of resistance to mercury. The most resistant microorganisms (Enterobacter cloacae, Klebsiella oxytoca, Serratia odorifera, and Saccharomyces cerevisiae) were tested for their ability to form biofilms in the presence and absence of mercury, both in polystyrene plates and on ABM carriers. The results showed that among planktonic forms, K. oxytoca was the most resistant. A biofilm of the same microorganisms was more than 10-fold resistant. Most consortia biofilms had MBEC values > 100,000 µg/mL. Among individual biofilms, E. cloacae showed the highest mercury removal efficiency (97.81% for 10 days). Biofilm consortia composed of three species showed the best ability to remove mercury (96.64%-99.03% for 10 days). This study points to the importance of consortia of different types of wastewater microorganisms in the form of biofilms and suggests that they can be used to remove mercury in wastewater treatment bioreactors.

A mini-review on indigenous microbial biofilm from various wastewater for heavy-metal removal - new trends.

Biofilm, as a form of the microbial community in nature, represents an evolutionary adaptation to the influence of various environmental conditions. In nature, the largest number of microorganisms occur in the form of multispecies biofilms. The ability of microorganisms to form a biofilm is one of the reasons for antibiotic resistance. The creation of biofilms resistant to various contaminants, on the other hand, improves the biological treatment process in wastewater treatment plants. Heavy metals cannot be degraded, but they can be transformed into non-reactive and less toxic forms. In this process, microorganisms are irreplaceable as they interact with the metals in a variety of ways. The environment polluted by heavy metals, such as wastewater, is also a source of undiscovered microbial diversity and specific microbial strains. Numerous studies show that biofilm is an irreplaceable strategy for heavy metal removal. In this review, we systematize recent findings regarding the bioremediation potential of biofilm-forming microbial species isolated from diverse wastewaters for heavy metal removal. In addition, we include some mechanisms of action, application possibilities, practical issues, and future prospects.

Food waste perceptions and reported behaviours during the first wave of the COVID-19 pandemic: Evidence from Bosnia and Herzegovina.

An increasing corpus of data demonstrated the disruptive impacts of the COVID-19 pandemic on food consumption habits, particularly food waste, but the Balkan area is often overlooked. Accordingly, this study investigates the immediate effects of the COVID-19 pandemic on consumer knowledge and reported behaviours linked to food waste in Bosnia and Herzegovina. The research was based on an online survey with 2425 participants using the Google forms platform from 10 April to 10 May 2020. This period coincided with the first wave of the COVID-19 pandemic in Bosnia and Herzegovina. Consumers' behaviours regarding where and how often they buy food, their attitude towards food labels, food provision and particularly the amounts and values of food waste and how they handle it were investigated. The data were analysed using descriptive statistics methods, and the significance of the association between variables was determined using nonparametric and multivariate statistical tests. The study's findings revealed that (i) Bosnia has a low rate of household food waste and a favourable attitude towards food waste prevention, (ii) the majority of the respondents are familiar with the most common expiry labels, notably 'use by' and 'best before' and (iii) consumers adjusted their buying and consumption patterns due to the pandemic. The findings of this research are essential for developing evidence-based policy in Bosnia and Herzegovina during the post-pandemic recovery period since they are unique to that country. Indeed, the crisis' lessons and insights may be used to help move towards more sustainable consumption habits.

Finding the best combination of autochthonous microorganisms with the most effective biosorption ability for heavy metals removal from wastewater.

The presence of heavy metals (HMs) in the environment represents a serious environmental problem. In this regard, this work was conceived with the aim of finding, among indigenous microorganisms, the species and their combinations with the best biosorption activity for the following HMs: zinc, lead, cadmium, copper, and nickel. The experiment was carried out in several steps: (1) isolation and identification of microbial strains from the Central Effluent Treatment Plant's wastewater; (2) studying the interaction of microorganisms and the ability to form biofilms in 96-well plates; (3) testing the resistance of biofilms to HMs; (4) testing the growth of biofilms on AMB media carriers in the presence of HMS; and (5) biosorption assay. The selected strains used in this study were: Enterobacter cloacae, Klebsiella oxytoca, Serratia odorifera, and Saccharomyces cerevisiae. The best biofilm producers in control medium were K. oxytoca/S. odorifera (KS), followed by K. oxytoca/S. odorifera/S. cerevisiae (KSC), and E. cloacae/K. oxytoca/S. odorifera (EKS) after 10 days of incubation. Mixed cultures composed of three species showed the highest resistance to the presence of all tested metals. The best biosorption capacity was shown by KSC for Cu2+ (99.18%), followed by EKS for Pb2+ (99.14%) and Cd2+ (99.03%), K. oxytoca for Ni2+ (98.47%), and E. cloacae for Zn2+ (98.06%). This research offers a novel approach to using mixed biofilms for heavy metal removal processes as well as its potential application in the bioremediation of wastewater.

Response of selected microbial strains and their consortia to the presence of automobile paints: Biofilm growth, matrix protein content and hydrolytic enzyme activity.

The goal of the current study was to examine the effects of pollutants (White color - CP; Metallic red color - FM; Thinner - CN; Thinner for rinsing paint - MF; Basic color (primer) - FH) originating from the automotive industry on the biofilm growth, matrix protein content, and activity of the hydrolytic enzymes of selected microbial strains in laboratory conditions that mimic the bioreactor conditions. The chosen microorganisms (bacteria, yeasts, and fungi) were isolated from automotive industry wastewater. Pure microbe cultures and their consortia were injected into AMB Media carriers and developed into biofilms. The use of AMB media carriers has been linked to an increase in the active surface area colonized by microorganisms. Afterwards, the carriers were transferred to Erlenmeyer flasks with nutrient media and pollutants at a concentration of 200 µL/mL. The current study found that, depending on the microbial strain, development phase, and chemical structure, the assessed pollutants had an inhibitory or stimulatory influence on the growth of single cultures and their consortia. Statistical analysis found positive correlations between the protein content in the matrix and the biofilm biomass of Rhodotorula mucilaginosa and consortia in CP and FH media, respectively. The proteolytic activity of Candida utilis was very pronounced in media with MF and CN. The best alkaline phosphatase activity (ALP) was achieved in the CN medium of R. mucilaginosa. Acid invertase activity was the highest in the FM and CP media of Escherichia coli and consortia, respectively, whereas the highest alkaline invertase activity was measured in the MF medium of E. coli. A positive correlation was confirmed between ALP and the biofilm biomass of R. mucilaginosa in CP and CN media, as well as between ALP and the biofilm biomass of Penicillium expansum in FM medium. The findings provide novel insights into the extracellular hydrolytic activity of the investigated microbial strains in the presence of auto paints, as well as a good platform for subsequent research into comprehensive biofilm profiling using modern methodologies.

Economic, ecological, and health aspects of ß-diketonate application in the process of water purification.

Water pollution is a constant challenge for humanity. Sustainable economic development and environmental protection through a green economy structure provide the opportunity to project a model of scientific, social, and economic flows. Considering new chemical use in water treatment, we tested two ß-diketonates that we previously synthesized in the reaction between methyl ketone and diethyl oxalate under basic conditions. For water treatment, we used the appropriate salts of the mentioned compounds due to better solubility in water. In cooperation with the partner organizations PUC (public utility companies) Kragujevac, LTD (Private Limited Company), "Rudnik," and FIAT (Fabbrica Italiana Automobili Torino), we conducted research on their wastewater treatment. The results appeared to be more convincing in practice than the conventional methods. As a result of the study, no negative effects exerted on living organisms were found. Therefore, we are on the right track for potential application in the treatment of drinking water. Appropriate ß-diketonates were tested on twelve microorganisms (isolates from the wastewater and standard strains of bacteria and yeast). One of the two tested compounds showed promising antimicrobial activity. Further investigations showed that the tested compounds significantly reduce the concentration of heavy metals, which was confirmed by statistical calculations. Also, the main advantage of this method is a small volume of waste requiring disposal, no need for driving off excess moisture, used recyclability of the coagulants, reducing hazardous waste, and therefore reducing the costs for water treatment.

Heavy metal tolerance and removal potential in mixed-species biofilm.

The aim of the study was to examine heavy metal tolerance (Cd2+, Zn2+, Ni2+ and Cu2+) of single- and mixed-species biofilms (Rhodotorula mucilaginosa and Escherichia coli) and to determine metal removal efficiency (Cd2+, Zn2+, Ni2+, Cu2+, Pb2+ and Hg2+). Metal tolerance was quantified by crystal violet assay and results were confirmed by fluorescence microscopy. Metal removal efficiency was determined by batch biosorption assay. The tolerance of the mixed-species biofilm was higher than the single-species biofilms. Single- and mixed-species biofilms showed the highest sensitivity in the presence of Cu2+ (E. coli-MIC 4 mg/ml, R. mucilaginosa-MIC 8 mg/ml, R. mucilaginosa/E. coli-MIC 64 mg/ml), while the highest tolerance was observed in the presence of Zn2+ (E. coli-MIC 80 mg/ml, R. mucilaginosa-MIC 161 mg/ml, R. mucilaginosa-E. coli-MIC 322 mg/ml). The mixed-species biofilm exhibited better efficiency in removal of all tested metals than single-species biofilms. The highest efficiency in Cd2+ removal was shown by the E. coli biofilm (94.85%) and R. mucilaginosa biofilm (97.85%), individually. The highest efficiency in Cu2+ (99.88%), Zn2+ (99.26%) and Pb2+ (99.52%) removal was shown by the mixed-species biofilm. Metal removal efficiency was in the range of 81.56%-97.85% for the single- and 94.99%-99.88% for the mixed-species biofilm.

Great horsetail (Equisetum telmateia Ehrh.): Active substances content and biological effects.

This paper deals with the antioxidant and antimicrobial activity, total phenolic content and concentrations of flavonoids of Equisetum telmateia extracts. Total phenolic content was determined with Folin-Ciocalteu reagent and it ranged between 129.0 to 262.7 mg GA/g. The concentration of flavonoids in various extracts of E. telmateia was determined using spectrophotometric method with aluminum chloride and obtained results varied from 112.6 to 199.8 mg RU/g. Antioxidant activity was monitored spectrophotometrically and expressed in terms of IC50 (µg/ml), and its values ranged from 33.4 to 982.2 µg/ml. The highest phenolic content, concentrations of flavonoids and capacity to neutralize DPPH radicals were found in the acetone extract. In vitro antimicrobial activity was determined using microdilution method. Minimum inhibitory concentration (MIC) and minimum microbicidal concentration (MMC) were also determined. Testing was performed on 22 microorganisms, including 15 strains of bacteria (standard and clinical strains) and 7 species of fungi. There were statistically significant differences in activity between the extracts of E. telmateia. Different effects were noticed against the bacteria and the methanol extract appeared to be most efficient. All the extracts showed significant antibacterial activity against G+ bacteria and weak to moderate activity against other microorganisms.