Mitja Kolar

Separation of heavy metals from water by functionalized glycidyl methacrylate poly (high internal phase emulsions)

Removal of silver, lead and cadmium ions from both model solutions and real contaminated water was achieved, in a flow through manner, by using highly porous functionalized poly(glycidyl methacrylate) materials, prepared by the polymerisation of high internal phase emulsions (polyHIPE), with significant sorption differences between metals allowing for selective removal. PolyHIPEs, initially prepared from glycidyl methacrylate as a functional monomer, were functionalized with pentaerythritol tetrakis(3-mercaptopropionate), 1,9-nonanedithiol and 2-aminobenzenethiol via the epoxy ring opening on the polymer supports and applied in a flow-through manner via encasements into dedicated disk holders. Capacity of 21.7mg Ag per gram of polymer was found for 1,9-nonanedithiol functionalized polymers, while the capacity was decreasing with the decreasing ionic radius of the metal; the dynamics of sorption also depended on metal ion size and furthermore on the thiol used for the polymer functionalization.

Cultivating conditions effects on kefiran production by the mixed culture of lactic acid bacteria imbedded within kefir grains

The influence of fermentation temperature, agitation rate, and additions of carbon sources, nitrogen sources, vitamins and minerals on production of kefiran by kefir grains lactic acid bacteria was studied in a series of experiments. The main aim of the work was to increase the exopolysaccharide (EPS) production where customised milk was used as fermentation medium. It was proved that the controlling of culturing conditions and the modifying of fermentation medium conditions (i.e., carbon, nitrogen, mineral sources and vitamins) can dramatically enhance the production of the EPS. The temperature and agitation rate were critical for kefiran production during the 24 h cultivation of grains; our optimised conditions being 25°C and 80 rpm, respectively. In addition, when optimising the effects of additional nutrition, it was found that 5% (w/v) lactose, 0.1% (w/v) thiamine, and 0.1% (w/v) FeCl3 led to the maximal production of EPS. The results indicate that nutrients can be utilised to improve the production of EPS and that good kefir grains growth does not appear to be a determining factor for a high production yield of EPS.

Modification of cellulose non-woven substrates for preparation of modern wound dressings

Different ways are presented of modifying cellulosic non-woven substrates, which can serve as potential wound dressings with satisfactory antimicrobial and hydrophilic properties. For safe attachment of silver particles without a measurable release from the used materials, a sol–gel derived process was used. Alkaline and oxygen plasma treatments were used to improve the hydrophilicity of the materials. Their efficiency was determined by measuring contact angles and water retention values. Scanning electron microscopy (SEM) was used for determination of sample morphology prior to and after treatment. The efficiency of silver attachment and activity was evaluated by in vitro release studies and antimicrobial tests. Atomic force microscopy (AFM) and SEM, combined with dynamic light scattering, were used for determination of silver particle size. Additionally, we evaluated the influence of treatment on technological parameters, important for application performance, i.e. mechanical properties and air permeability.

Antimicrobial efficiency evaluation by monitoring potassium efflux for cellulose fibres functionalised by chitosan

Abstract As there is a large gap in the field of fibre microbiological testing, the successful establishment of appropriate techniques is extremely appreciated. Antimicrobials prevent bacterial cell division by damaging the cell wall or affecting the permeabilities of cells’ membranes; they denature proteins, block enzyme activity, prevent cell survival, etc. Intracellular potassium cations are released by the inhibitions of pathogenic micro-organisms. Their quantitative determination enables monitoring of the bactericidal effect regarding antimicrobials. It can be used as an alternative technique for determining the inhibition of micro-organisms in contact with antimicrobial agents. Chitosan, a biodegradable natural polymer, possesses antimicrobial characteristics that depend on a number of factors such as the protonated amino groups’ quantities, degree of acetylation, molecular weight, solvents, etc. Over recent years chitosan has become extremely attractive for fibre functionalization usage. The aim of this paper was to apply spectrophotometry and potentiometry using potassium ion-selective electrode, respectively, for the quantitative analysis of potassium efflux, resulting from the degradation of micro-organisms’ membranes in contact with chitosan itself, as well as with cellulose fibres functionalised by chitosan.

Tailoring morphological features of cross-linked emulsion-templated poly(glycidyl methacrylate)

Porous poly(glycidyl methacrylate-co-ethyleneglycol dimethacrylate) samples with total porosity up to 91% were prepared by the polymerisation of high internal phase emulsions (HIPEs). Morphological features like cavity and interconnecting pore diameter were investigated and successfully controlled by changing the initiator system, surfactant ratio, pore volume ratio, stirring rate and reaction mixture temperature. All resulting porous polyHIPE monoliths had open cellular morphology with cavity diameters between sub-μm and 30 μm.