Browsing by Author "Ševců, Alena"

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    An across-species comparison of the sensitivity of different organisms to Pb-based perovskites used in solar cells
    (ELSEVIER, RADARWEG 29, 1043 NX AMSTERDAM, NETHERLANDS, 2020) Wang, Guiyin; Zhai, Yujia; Zhang, Shirong; Diomede, Luisa; Bigini, Paolo; Romeo, Margherita; Cambier, Sebastien; Contal, Servane; Nguyen, Nhung H. A.; Rosická, Petra; Ševců, Alena; Nickel, Carmen; Vijver, Martina G.; Peijnenburg, Willie J. G. M.
    Organic-inorganic perovskite solar cells (PSCs) are promising candidates as photovoltaic cells. Recently, they have attracted significant attention due to certified power conversion efficiencies exceeding 23%, low-cost engineering, and superior electrical/optical characteristics. These PSCs extensively utilize a perovskite-structured composite with a hybrid of Pb-based nanomaterials. Operation of them may cause the release of Pb-based nanoparticles. However, limited information is available regarding the potential toxicity of Pb-based PSCs on various organisms. This study conducted a battery of in vitro and in vivo toxicity bioassays for three quintessential Pb-based PSCs (CH3NH3PbI3, NHCHNH3PbBr3, and CH3NH3PbBr3) using progressively more complex forms of life. For all species tested, the three different perovskites had comparable toxicities. The viability of Caco-2/TC7 cells was lower than that of A549 cells in response to Pbbased PSC exposure. Concentration-dependent toxicity was observed for the bioluminescent bacterium Vibrio fischeri, for soil bacterial communities, and for the nematode Caenorhabditis elegans. Neither of the tested Pb-based PSCs particles had apparent toxicity to Pseudomonas putida. Among all tested organisms, V. fischeri showed the highest sensitivity with EC50 values (30 min of exposure) ranging from 1.45 to 2.91 mg L-1. Therefore, this study recommends that V. fischeri should be preferably utilized to assess. PSC toxicity due to its increased sensitivity, low costs, and relatively high throughput in a 96-well format, compared with the other tested organisms. These results highlight that the developed assay can easily predict the toxic potency of PSCs. Consequently, this approach has the potential to promote the implementation of the 3Rs (Replacement, Reduction, and Refinement) principle in toxicology and decrease the dependence on animal testing when determining the safety of novel PSCs.
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    Biodegradation of High Concentrations of Aliphatic Hydrocarbons in Soil from a Petroleum Refinery: Implications for Applicability of New Actinobacterial Strains
    (MDPI, 2019-11-09) Trögl, Josef; Esuola, Catherine Olwakemi; Kříženecká, Sylvie; Kuráň, Pavel; Seidlová, Lenka; Veronesi-Dáňová, Petra; Popelka, Jan; Babalola, Olubukola Oluranti; Hrabák, Pavel; Czinnerová, Marie; Kakosová, Eva; Ševců, Alena; Tischler, Dirk
    At present, there is great demand for new resistant and metabolically active strains of biodegrading bacteria capable of degrading high concentrations of petroleum pollutants. In this study, we undertook a series of pot-based biodegradation experiments on soil from a petroleum refinery lagoon heavily polluted with aliphatic hydrocarbons (81.6 ± 2.5 g·kg−1 dry weight) and metals. Periodical bioaugmentation with either a mixture of isolated degraders identified as Bacillus sp. and Ochrobactrum sp. or biostimulation with nutrient medium, singly or in combination, did not produce any significant decrease in hydrocarbons, even after 455 days. Inoculation with Gordonia rubripertincta CWB2 and Rhodococcus erythropolis S43 in iron-limited media, however, resulted in a significant decrease in hydrocarbons 45 days after bioaugmentation. These actinobacterial strains, therefore, show significant potential for bioremediation of such highly polluted soils.
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    Charakterizace nanomateriálů z hlediska jejich chování a transformace v environmentálně relevantních prostředích
    (Technická Univerzita v Liberci, 2014) Štryncl, Martin; Ševců, Alena
    Interactions of iron-based nanoparticles with river water and reservoir water were studied in this diploma thesis. NANOFER STAR, Carbo-Iron and ferrihydrite were selected as the representatives of the iron-based nanoparticles. NANOFER STAR is commercially produced for remediation of contaminated soils and ground waters and Carbo-Iron is studied as promising material for advanced application in remediation technologies and thus they would be purposely in contact with the natural environment. Ferrihydrite is a naturally occurring material, here served as a control inert nanoparticle. The study interest was in fate of these nanoparticles in environmentally relevant media. The main objectives were: i) to describe what happens when iron-based nanoparticles are released into aqueous environment; ii) to characterize the nanoparticles using different methods and analyses; iii) to assess potential toxicity of newly prepared and aged nanoparticle suspensions using model bacteria Escherichia coli. Real river water samples were obtained from St. Annes Park in Dublin (Irish Republic) and real reservoir water samples were obtained from Harcov reservoir in Liberec (Czech Republic). The nanoparticle suspensions were dispersed in the river water, in the reservoir water and also ultra-pure water and model river water were used. Ultra-pure water was selected as a control dispersive medium without organic matter and other natural compounds and the model RW was created to mimic the river water. The suspensions and nanoparticles were investigated using selected techniques such as Electrophoretic Light Scattering (ELS), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (SEM/EDS), Atomic Force Microscopy (AFM), Brunauer-Emmett-Teller surface area analysis (BET), and the media were characterized based on their pH, Oxidation Reduction Potential (ORP), oxygen concentration, conductivity, temperature, Total Organic Carbon (TOC) and Total Phosphorus (TP). The results in general showed that all particles in the river or the reservoir water increased in diameter over one month. Natural compounds in real environmental media resulted in decrease of electrostatic repulsion and increase in diameter of aggregates. The nanoparticles dispersed in model river water did not behave in a similar way as in natural river water, probably due to lower concentration of TOC and higher conductivity. Moreover, as a consequence of larger size and higher density (about 1 ?m and 5 g/ml) of particles, the aggregates and strong sedimentation were observed. Experimental data revealed weakness of the DLS method for dynamic size distribution analysis of nanoparticles of higher density such as iron. The iron-based nanoparticles were too heavy and unstable in aqueous environment and therefore it was impossible to get reliable data. Nevertheless, DCS is a promising method for iron-based particle analysis. Finally, the toxicity of iron-based nanoparticles tested on Escherichia coli was not observed neither in newly prepared nor in aged nanoparticle suspensions.
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    Combining nanoscale zero-valent iron with electrokinetic treatment for remediation of chlorinated ethenes and promoting biodegradation: A long-term field study
    (PERGAMON-ELSEVIER SCIENCE LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND, 2020) Czinnerová, Marie; Voluščuková, Ondřejka; Marková, Kristýna; Ševců, Alena; Černík, Miroslav; Nosek, Jaroslav
    Nanoscale zero-valent iron (nZVI) is recognized as a powerful tool for the remediation of groundwater contaminated by chlorinated ethenes (CEs). This long-term field study explored nZVI-driven degradation of CEs supported by electrokinetic (EK) treatment, which positively affects nZVI longevity and migration, and its impact on indigenous bacteria. In particular, the impact of combined nZVI-EK treatment on organohalide-respiring bacteria, ethenotrophs and methanotrophs (all capable of CE degradation) was assessed using molecular genetic markers detecting Dehalococcoides spp., Desulfitobacterium spp., the reductive dehalogenase genes vcrA and bvcA and ethenotroph and methanotroph functional genes. The remediation treatment resulted in a rapid decrease of the major pollutant cis-1,2-dichloroethene (cDCE) by 75% in the affected area, followed by an increase in CE degradation products methane, ethane and ethene. The newly established geochemical conditions in the treated aquifer not only promoted growth of organohalide-respiring bacteria but also allowed for the concurrent presence of vinyl chloride- and cDCE-oxidizing methanotrophs and (especially) ethenotrophs, which proliferated preferentially in the vicinity of an anode where low levels of oxygen were produced. The nZVI treatment resulted in a temporary negative impact on indigenous bacteria in the application well close to the cathode; but even there, the microbiome was restored within 15 days. The nZVI-EK treatment proved highly effective in reducing CE contamination and creating a suitable environment for subsequent biodegradation by changing groundwater conditions, promoting transport of nutrients and improving CE availability to soil and groundwater bacteria.
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    Fabrication, Characterization, and Antibacterial Properties of Electrospun Membrane Composed of Gum Karaya, Polyvinyl Alcohol, and Silver Nanoparticles
    (Hindawi Publishing Corporation, 2015) Padil, Vinod Vellora Thekkae; Nguyen, Nhung H. A.; Ševců, Alena; Černík, Miroslav
    Gum karaya (GK), a natural hydrocolloid, was mixed with polyvinyl alcohol (PVA) at different weight ratios and electrospun to produce PVA/GK nanofibers. An 80 : 20 PVA/GK ratio produced the most suitable nanofiber for further testing. Silver nanoparticles (Ag-NPs) were synthesised through chemical reduction of AgNO3 (at different concentrations) in the PVA/GK solution, the GK hydroxyl groups being oxidised to carbonyl groups, and Ag+ cations reduced to metallic Ag-NPs. These PVA/GK/Ag solutions were then electrospun to produce nanofiber membranes containing Ag-NPs (Ag-MEMs). Membrane morphology and other characteristics were analysed using scanning electron microscopy coupled with energy dispersive X-ray analysis, transmission electron microscopy, and UV-Vis and ATR-FTIR spectroscopy. The antibacterial activity of the Ag-NP solution and Ag-MEM was then investigated against Gram-negative Escherichia coli and Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus. Our results show that electrospun nanofiber membranes based on natural hydrocolloid, synthetic polymer, and Ag-NPs have many potential uses in medical applications, food packaging, and water treatment.
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    Functionalized Magnetic Nanoparticles and Their Effect on Escherichia coli and Staphylococcus aureus
    (Hindawi Publishing Corporation, 2015) Darwish, Mohamed S. A.; Nguyen, Nhung H. A.; Ševců, Alena; Stibor, Ivan
    Magnetite (Fe3O4) nanoparticles were prepared using coprecipitation and subsequently surface-functionalized with 3-aminopropyltriethoxysilane (APTS), polyethylene glycol (PEG), and tetraethoxysilane (TEOS). Nanoparticle morphology was characterized using scanning electron microscopy, while structure and stability were assessed through infrared spectroscopy and zeta potential, respectively. Average size of the nanoparticles analysed by dynamic light scattering was 89 nm, 123 nm, 109 nm, and 130 nm for unmodified magnetite and APTS-, PEG-, and TEOS-modified magnetite nanoparticles, respectively. Biological effect was studied on two bacterial strains: Gram-negative Escherichia coli CCM 3954 and Gram-positive Staphylococcus aureus CCM 3953. Most of modified magnetite nanoparticles had a significant effect on S. aureus and not on E. coli, whereas PEG- magnetite nanoparticles displayed no significant effect on the growth rate of either bacteria.
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    Microbially influenced corrosion of carbon steel in the presence of anaerobic sulphate-reducing bacteria
    (TAYLOR & FRANCIS LTD, 2-4 PARK SQUARE, MILTON PARK, ABINGDON OR14 4RN, OXON, ENGLAND, 2019) Černoušek, Tomáš; Shrestha, Rojina; Kovářová, Hana; Špánek, Roman; Ševců, Alena; Sihelská, Kristína; Kokinda, Jakub; Stoulil, Jan; Steinová, Jana
    Carbon steel is currently being considered as a candidate canister material for use in a deep geological repository of radioactive waste. Assessment of canister material corrosion through microbial activity is an important part of the safety assessment for the final repository. The aim of study was to compare and characterise the corrosion behaviour of carbon steel under sterile and non-sterile anaerobic conditions in natural groundwater containing sulphate-reducing bacteria (SRB). A molecular-biological approach was used to determine the presence and abundance changes of relevant bacterial groups. Carbon steel corrosion rates were higher in the presence of SRB compared with sterile control. EIS described the evolution of three time-constants under non-sterile conditions, while scanning electron microscopy confirmed that the carbon steel surface was covered with a two-layer biofilm. Molecular-biological analysis of the water and biofilm indicated the dominance of SRB, with Desulfomicrobium and Desulfovibrio species prevalent.
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    Polyamide-Laccase Nanofiber Membrane for Degradation of Endocrine-Disrupting Bisphenol A, 17 alpha-ethinylestradiol, and Triclosan
    (MDPI, 2019) Maryšková, Milena; Rysová, Miroslava; Novotný, Vít; Ševců, Alena
    Contamination of potable water by endocrine disrupting chemicals (EDCs) is a growing problem worldwide. One of the possible treatments is the utilization of laccase enzyme catalyzing oxidation of phenolic structures of EDC when anchored in a polymeric nanofiber membrane. Previous studies failed to develop a membrane with a sufficiently active enzyme, or the immobilization process was too complicated and time-consuming. Here, we established an elegant method for immobilizing Trametes versicolor laccase onto polyamide 6 nanofibers (PA6-laccase) via adsorption and glutaraldehyde crosslinking, promoting high enzyme activity and easier applicability in water treatment technology. This simple and inexpensive immobilization ensures both repeated use, with over 88% of initial activity retained after five ABTS catalytic cycles, and enhanced storage stability. PA6-laccase was highly effective in degrading a 50-mu M EDC mixture, with only 7% of bisphenol A, 2% of 17 alpha-ethinylestradiol, and 30% of triclosan remaining after a 24-h catalytic process. The PA6-laccase membrane can lead to the improvement of novel technologies for controlling of EDC contamination in potable water.
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    Polyamide-laccase nanofiber membrane for degradation of endocrine-disrupting bisphenol A, 17α-ethinylestradiol, and triclosan
    (MDPI, 2019-10) Maryšková, Milena; Rysová, Miroslava; Novotný, Vít; Ševců, Alena
    Contamination of potable water by endocrine disrupting chemicals (EDCs) is a growing problem worldwide. One of the possible treatments is the utilization of laccase enzyme catalyzingoxidation of phenolic structures of EDC when anchored in a polymeric nanofiber membrane. Previous studies failed to develop a membrane with a suficiently active enzyme, or the immobilization process was too complicated and time-consuming. Here, we established an elegant method for immobilizing Trametes versicolor laccase onto polyamide 6 nanofibers (PA6-laccase) via adsorption and glutaraldehyde crosslinking, promoting high enzyme activity and easier applicability in water treatment technology. This simple and inexpensive immobilization ensures both repeated use, with over 88% of initial activity retained after five ABTS catalytic cycles, and enhanced storage stability. PA6-laccase was highly effective in degrading a 50-M EDC mixture, with only 7% of bisphenol A, 2% of 17α-ethinylestradiol, and 30% of triclosan remaining after a 24-h catalytic process. The PA6-laccase membrane can lead to the improvement of novel technologies for controlling of EDC contamination in potable water.
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    Strategies adopted by Aphanizomenon flos-aquae in response to phosphorus deficiency and their role on growth
    (SPRINGEROPEN, CAMPUS, 4 CRINAN ST, LONDON, N1 9XW, ENGLAND, 2020-03-16) Chen, Xiaoyan; Dolinová, Iva; Ševců, Alena; Jurczak, Tomasz; Frankiewicz, Piotr; Wojtal-Frankiewicz, Adrianna; Wan, Lingling; Deng, Qinghui; Song, Chunlei; Zhou, Yiyong; Cao, Xiuyun
    Background The N-2-fixing cyanobacterium, Aphanizomenon flos-aquae is a globally distributed bloom causing species that degrades water quality of fresh and marine water bodies. Overcoming phosphorus (P) deficiency is one of the ecological advantages for bloom-forming cyanobacteria. It remains unclear to what extent can A. flos-aquae alleviate P deficiency by regulating P using strategies. Results Based on in situ observations of extracellular alkaline phosphatase (APase) in A. flos-aquae via enzyme-labeled fluorescence in freshwater bodies in China, Poland and Czechia, we further investigated responses of isolated A. flos-aquae to different P supplies (dissolved inorganic P (Pi) as +DIP, dissolved organic alpha-glycerophosphate and beta-glycerophosphate as +DOP alpha and +DOP beta, P-free condition as P-depleted). The significantly negative relationships between percentage of APase producing cells and soluble reactive P concentration in both fields and cultures suggested that the excretion of APase in cyanobacterium was regulated by ambient Pi supply. Suffering from P deficiency in the P-depleted treatments, A. flos-aquae showed the highest APase activity but a vigorous growth at the early culture stage, which might also benefit from the formation of polyphosphate body (PPB) and the decrease of cell P quota. In the +DOP treatments, the coordination of dissolved DOP mineralization and continuous prompt utilization of PPB might contribute to a maintenance but not reproduction of A. flos-aquae when relying on DOP, since the specific growth rate kept around 0 cells L-1 day(-1) at the second half culture period and the highest cell density reached only 13.38% of that in +DIP treatments while photochemical efficiency was comparable during the whole experiment. Luxury uptake of phosphate as PPB in the +DIP treatments was consistent to the canonical view of polyphosphate as P storage. Conclusion Aphanizomenon flos-aquae could achieve an instantaneous growth in response to P deficiency with the coordination of P utilization strategies, while it maintained a long-term sustainable growth but not reproduction under sole DOP supply. Persistent and active reproduction could only be achieved in high Pi supply, which implying that an effective consequence can be expected for combating the bloom of A. flos-aquae when controlling P supply.