Jeanna Starosvetsky

Whole Cell Imprinting in Sol-Gel Thin Films for Bacterial Recognition in Liquids: Macromolecular Fingerprinting

Thin films of organically modified silica (ORMOSILS) produced by a sol-gel method were imprinted with whole cells of a variety of microorganisms in order to develop an easy and specific probe to concentrate and specifically identify these microorganisms in liquids (e.g., water). Microorganisms with various morphology and outer surface components were imprinted into thin sol-gel films. Adsorption of target microorganism onto imprinted films was facilitated by these macromolecular fingerprints as revealed by various microscopical examinations (SEM, AFM, HSEM and CLSM). The imprinted films showed high selectivity toward each of test microorganisms with high adsorption affinity making them excellent candidates for rapid detection of microorganisms from liquids.

Effect of iron exposure in SRB media on pitting initiation

Pitting corrosion of iron (99.9%) in Sulphate-reducing bacteria (SRB) media containing 0.09–0.30 g/l sulphides and 0.1–5.0 g/l [Cl−] was studied. Iron electrode immersed in SRB media undergoes fast activation and numerous active sites formed on the surface. Depending on exposure time, pitting was initiated at different potentials. After short period (<2 h) in open circuit potential, when active sites were still exist on the surface, pitting occurred at the potential range of −0.60 to −0.55 V (SCE). Extended exposures resulted in more stable passivity of iron and the pitting potential shifted to positive values. Pit initiation mechanism at the various exposure periods is discussed.

Combined chemical-biological treatment for prevention/rehabilitation of clogged wells by an iron-oxidizing bacterium.

Groundwater wells containing large concentrations of ferrous iron face serious clogging problems as a result of biotic iron oxidation. Following a short time after their start off, wells get clogged, and their production efficiency drop significantly up to a total obstruction, making cleanup and rehabilitation an economic burden. The present study was undertaken to test an experimental combined treatment (chemical and biological) for future prevention or rehabilitation of clogged wells. Sphaerotilus natans (an iron-oxidizing bacterium) freshly isolated from a deep well was grown to form biofilms on two systems: coupons and sand buried miniature wedge wire screen baskets. A combined chemical-biological treatment, applied at laboratory scale by use of glycolic acid (2%) and isolated bacteriophages against Sphaerotilus natans (SN1 and ER1-a newly isolated phage) at low multiplicity of infection (MOI), showed inhibition of biofilm formation and inactivation of the contaminant bacteria. In addition to complete inactivation of S. natans planktonic bacteria by the respective phages, earlier biofilm treatment with reduced glycolic acid concentration revealed efficient exopolysaccharide (EPS) digestion allowing phages to be increasingly efficient against biofilm matrix bacteria. Utilization of this combined treatment revealed clean surfaces of a model stainless steel wedge wire screen baskets (commonly used in wells) for up to 60 days.

Adsorption of flavobacterium breve and pseudomonas fluorescens p17 on different metals: Electrochemical polarization effect

The electrochemical polarization effect on early adsorption of Flavobacterium breve and Pseudomonas fluorescens P17 to platinum, titanium, stainless steel, copper, aluminum alloy and mild steel was studied. A well‐defined peak characterized the bacterial adsorption dependence on externally applied potential. Maximal adsorption occurred in the potential range of ‐0.5 to 0.5 V (SCE) for all tested metals. A shift of applied potential towards both a positive and a negative direction from the maximal adsorption potential (Emax,ad) was accompanied by a gradual decrease in bacterial adsorption. The extent of bacterial adsorption strongly depended on the nature of the metallic substratum and decreased accordingly as follows: platinum > titanium > stainless steel > aluminum alloy > carbon steel > copper. Adsorption on all tested metals was approximately two orders of magnitude higher with the relatively more hydrophobic F. breve compared to the less hydrophobic P. fluorescens P17. The effect of electrochemical polarization on the initial stages of bacterial adsorption onto metallic substrata is further discussed.

Co-cultivation of microalgae and nitrifiers for higher biomass production and better carbon capture

The aim of this work was to study co-cultivation of nitrifiers with microalgae as a non-intrusive technique for selective removal of oxygen generated by microalgae. Biomass concentration was, at least, 23% higher in mixed-cultures where nitrifiers kept the dissolved oxygen concentration below 9.0μLL(-1) than in control Chlorella vulgaris axenic-cultures where the concentration of dissolved oxygen was higher than 10.0μLL(-1). This approach to eliminating oxygen inhibition of microalgal growth could become the basis for the development of advanced microalgae reactors for removal of CO2 from the atmosphere, and concentrated CO2 streams. CO2 sequestration would become a chemically and geologically safer and environmentally more sound technology provided it uses microalgal, or other biomass, instead of CO2, for carbon storage.

Preparation of biodegradable xanthan-glycerol hydrogel, foam, film, aerogel and xerogel at room temperature.

Polymers, hence hydrogels, pollute waters and soils accelerating environmental degradation. Environmentally benign hydrogels were made in water from biodegradable xanthan (X) and glycerol (G) at 22.5±2.5°C. Molar ratio [G]/[X]<3.0 was used to maximize crosslinking by mono-glycerol instead by poly-glycerol. XG-hydrogels were transformed into: XG-foams, XG-films, and XG-aerogel. Anionic character of XG-materials changes with changing [G]/[X] ratio. XG-films made from XG-hydrogels absorb up to 40 times more water than XG-films made from XG-foams. The films made from XG-foams and HCl do not dissolve in water during 48h. Making XG-materials is a no-waste process which decreases pollution, eliminates waste disposal costs, and minimizes energy expenses. XG-materials are suitable for both industrial and environmental applications including slow release and concentration of cations. XG-materials, made of xanthan, microbial polysaccharide, could also be used in applications targeting populations that do not consume meat or meat based products.

TiO2 P-25 anatase rapid precipitation from water by use of struvite formation.

UV(360nm) irradiation of TiO(2) P-25 nanoparticle in water suspension is used for photocatalytic mineralization of pollutants or inactivation of microorganisms. Removal of TiO(2) particles from large volumes of water following photocatalytic process is problematic due to their nano-size. So far no chemical methods are available for TiO(2) rapid precipitation while filtration or centrifugation is not feasible because of high cost and limited performance. In the present study TiO(2) was rapidly precipitated from water suspension by formation of the mineral struvite. Addition of Mg, P, and NH(4)(+) at stochiometric rates of 1:1:1 at pH>8.3 resulted in TiO(2) entrapment into struvite formed flocs and rapid precipitation. Struvite sludge formed and precipitated was observed under HSEM revealing TiO(2) entrapment into struvite mineral.