1. Biofilm surface density determines biocide effectivenessSara Baš, Mateja Kramer, David Stopar, 2017, original scientific article Abstract: High resistance of biofilms for chemical challenges is a serious industrial and medical problem. In this work a gradient of surface covered with biofilm has been produced and correlated to the effectiveness of different commercially available oxidative biocides. The results for thin Escherichia coli biofilms grown in rich media supplemented with glucose or lactose on glass or poly methyl methacrylate surfaces indicate that the effectiveness of hydrogen peroxide or chlorine dioxide and quaternary ammonium compounds is inversely proportional to the fraction of the surface covered with the biofilm. In areas where biofilm covered more than 90% of the available surface the biocide treatment was inefficient after 60 min of incubation. The combined effect of oxidant and surfactant increased the effectiveness of the biocide. On the other hand, the increased biofilm viscoelasticity reduced biocide effectiveness. The results emphasize differential biocide effectiveness depending on the fraction of the attached bacterial cells. The results suggest that biofilm biocide resistance is an acquired property that increases with biofilm maturation. The more dense sessile structures present lower log reductions compared to less dense ones.
Keywords: biofilms, E. coli, biocide, antimicrobial, surface coverage, viscoelasticity
Published in DiRROS: 24.07.2024; Views: 21; Downloads: 11
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2. Sequestration of polystyrene microplastics by jellyfish mucusŽiva Lengar, Katja Klun, Iztok Dogša, Ana Rotter, David Stopar, 2021, original scientific article Abstract: The worldwide microplastics pollution is a serious environmental and health problem that is currently not effectively mitigated. In this work we tested jellyfish mucus as a new bioflocculent material capable of sequestration of polystyrene microplastics in aqueous environments. Mucus material was collected from different jellyfish species and was used to trap fluorescently tagged polystyrene microspheres. The efficiency of removal was tested using varying concentrations of microplastics and mucus. The interaction between the microplastics and mucus was determined by viscosity measurements and confocal laser scanning microscopy. Different mucus preparation methods were also tested: freshly prepared, mechanically sheared, freeze-thawed, freeze-dried, and hydrolyzed mucus. The results demonstrate that jellyfish mucus can efficiently sequester polystyrene microplastics particles from the suspension. The fraction of the removed microplastics was highest with freshly prepared mucus and decreased with freeze-thawing and freeze-drying. The mucus ability to sequester microplastics was completely lost in the hydrolyzed mucus. The results imply that the intact jellyfish mucus has the potential to be used as a biopolymer capable of removing microplastics material.
Published in DiRROS: 19.07.2024; Views: 54; Downloads: 31
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3. Parameters for discrimination between organic and conventional production : a case study for chicory plants (Cichorium intybus L.)Lovro Sinkovič, Marijan Nečemer, Nives Ogrinc, Dragan Žnidarčič, David Stopar, Rajko Vidrih, Vladimir Meglič, 2020, original scientific article Keywords: Organic production, Conventional production, Chicory plant, Bioactive compounds, Fertility management, Isotopic signature, Multi-elemental profile, Nitrogen assimilation
Published in DiRROS: 11.05.2020; Views: 2624; Downloads: 977
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