Home  About us  Contact
 

Iron Oxidation (iron + oxidation)

Distribution by Scientific Domains
Life Sciences88%

Kinds of Iron Oxidation

  • ferrous iron oxidation
    		•

    Selected Abstracts

    Dissimilatory ferrous iron oxidation at a low pH: a novel trait identified in the bacterial subclass Rubrobacteridae

    FEMS MICROBIOLOGY LETTERS, Issue 2 2008
    Christopher G. Bryan
    Abstract A novel iron-oxidizing acidophilic actinobacterium was isolated from spoil material at an abandoned copper mine. Phylogenetic analysis placed the isolate within the Rubrobacteridae subclass of the Actinobacteria. Its optimum temperature and pH for growth are 30,35 °C and pH 3.0, respectively. Although it could catalyze the dissimilatory oxidation of ferrous iron, growth yields declined progressively in media containing ferrous iron concentrations >100 ,M. The isolate, Pa33, did not grow or oxidize iron in the absence of organic carbon, and appeared to be an obligate heterotroph. Specific rates of iron oxidation were much smaller than those determined for the autotrophic iron-oxidizing proteobacterium Acidithiobacillus ferrooxidans and the heterotrophic iron-oxidizing actinobacterium Ferrimicrobium acidiphilum. Iron oxidation by isolate Pa33 appears to be a defensive mechanism, in which iron oxidation converts a soluble species to which the bacterium is sensitive to an oxidized species (ferric iron) that is highly insoluble in the spoil from which it was isolated. This is the first report of acidophily or dissimilatory iron oxidation within the Rubrobacteridae subclass and one of very few within the Actinobacteria phylum as a whole. [source]

    Stoichiometric model and metabolic flux analysis for Leptospirillum ferrooxidans

    BIOTECHNOLOGY & BIOENGINEERING, Issue 4 2010
    M.P. Merino
    Abstract A metabolic model for Leptospirillum ferrooxidans was developed based on the genomic information of an analogous iron oxidizing bacteria and on the pathways of ferrous iron oxidation, nitrogen and CO2 assimilation based on experimental evidence for L. ferrooxidans found in the literature. From this metabolic reconstruction, a stoichiometric model was built, which includes 86 reactions describing the main catabolic and anabolic aspects of its metabolism. The model obtained has 2 degrees of freedom, so two external fluxes were estimated to achieve a determined and observable system. By using the external oxygen consumption rate and the generation flux biomass as input data, a metabolic flux map with a distribution of internal fluxes was obtained. The results obtained were verified with experimental data from the literature, achieving a very good prediction of the metabolic behavior of this bacterium at steady state. Biotechnol. Bioeng. 2010;107:696,706. © 2010 Wiley Periodicals, Inc. [source]

    Development and calibration of a nitrification PDE model based on experimental data issued from biofilter treating drinking water

    BIOTECHNOLOGY & BIOENGINEERING, Issue 2 2006
    I. Queinnec
    Abstract To remove ammonia for production of drinking water, nitrification can be performed in a bio-filter. At least 1 month is necessary to capture from the groundwater and then grow a sufficient amount of nitrifying bacteria to reach the desired removal efficiency. Improving start-up of bio-filters at low substrate concentration is therefore a major challenge. In this connection, it is important to develop appropriate models for designing, monitoring or analysing biofilm systems during start-up or following disinfection events. This study discusses the development and calibration of a nitrification PDE model which reflects the compromise between the complexity associated with the description of the full physical and biochemical mechanisms and the search for a simplified model with identifiable parameters. This model takes only the relevant phenomena (considering the full operating range) into account. The validity of the calibrated model has been evaluated through experiments under very different operational conditions, at the laboratory and under real industrial conditions, involving the full upstream chain of water treatment (iron oxidation and sand filter). © 2006 Wiley Periodicals, Inc. [source]

    Ferrous iron oxidation by foam immobilized Acidithiobacillus ferrooxidans: Experiments and modeling

    BIOTECHNOLOGY PROGRESS, Issue 5 2009
    S. Jaisankar
    Abstract Ferrous iron bio-oxidation by Acidithiobacillus ferrooxidans immobilized on polyurethane foam was investigated. Cells were immobilized on foams by placing them in a growth environment and fully bacterially activated polyurethane foams (BAPUFs) were prepared by serial subculturing in batches with partially bacterially activated foam (pBAPUFs). The dependence of foam density on cell immobilization process, the effect of pH and BAPUF loading on ferrous oxidation were studied to choose operating parameters for continuous operations. With an objective to have high cell densities both in foam and the liquid phase, pretreated foams of density 50 kg/m3 as cell support and ferrous oxidation at pH 1.5 to moderate the ferric precipitation were preferred. A novel basket-type bioreactor for continuous ferrous iron oxidation, which features a multiple effect of stirred tank in combination with recirculation, was designed and operated. The results were compared with that of a free cell and a sheet-type foam immobilized reactors. A fivefold increase in ferric iron productivity at 33.02 g/h/L of free volume in foam was achieved using basket-type bioreactor when compared to a free cell continuous system. A mathematical model for ferrous iron oxidation by Acidithiobacillus ferrooxidans cells immobilized on polyurethane foam was developed with cell growth in foam accounted by an effectiveness factor. The basic parameters of simulation were estimated using the experimental data on free cell growth as well as from cell attachment to foam under nongrowing conditions. The model predicted the phase of both oxidation of ferrous in shake flasks by pBAPUFs as well as by fully activated BAPUFs for different cell loadings in foam. Model for stirred tank basket bioreactor predicted within 5% both transient and steady state of the experiments closely for the simulated dilution rates. Bio-oxidation at high Fe2+ concentrations were simulated with experiments when substrate and product inhibition coefficients were factored into cell growth kinetics. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source]

    Functional studies of frataxin

    ACTA PAEDIATRICA, Issue 2004
    G Isaya
    Mitochondria generate adenosine triphosphate (ATP) but also dangerous reactive oxygen species (ROS). One-electron reduction of dioxygen in the early stages of the electron transport chain yields a superoxide radical that is detoxified by mitochondrial superoxide dismutase to give hydrogen peroxide. The hydroxyl radical is derived from decomposition of hydrogen peroxide via the Fenton reaction, catalyzed by Fe2+ ions. Mitochondria require a constant supply of Fe2+ for heme and iron-sulfur cluster biosyntheses and therefore are particularly susceptible to ROS attack. Two main antioxidant defenses are known in mitochondria: enzymes that catalytically remove ROS, e.g. superoxide dismutase and glutathione peroxidase, and low molecular weight agents that scavenge ROS, including coenzyme Q, glutathione, and vitamins E and C. An effective defensive system, however, should also involve means to control the availability of pro-oxidants such as Fe2+ ions. There is increasing evidence that this function may be carried out by the mitochondrial protein frataxin. Frataxin deficiency is the primary cause of Friedreich's ataxia (FRDA), an autosomal recessive degenerative disease. Frataxin is a highly conserved mitochondrial protein that plays a critical role in iron homeostasis. Respiratory deficits, abnormal cellular iron distribution and increased oxidative damage are associated with frataxin defects in yeast and mouse models of FRDA. The mechanism by which frataxin regulates iron metabolism is unknown. The yeast frataxin homologue (mYfhlp) is activated by Fe(II) in the presence of oxygen and assembles stepwise into a 48-subunit multimer (,48) that sequesters <2000 atoms of iron in a ferrihydrite mineral core. Assembly of mYfhlp is driven by two sequential iron oxidation reactions: a fast ferroxidase reaction catalyzed by mYfh1p induces the first assembly step (,,3), followed by a slower autoxidation reaction that promotes the assembly of higher order oligomers yielding ,48. Depending on the ionic environment, stepwise assembly is associated with the sequestration of 50,75 Fe(II)/subunit. This Fe(II) is initially loosely bound to mYfh1p and can be readily mobilized by chelators or made available to the mitochondrial enzyme ferrochelatase to synthesize heme. However, as iron oxidation and mineralization proceed, Fe(III) becomes progressively inaccessible and a stable iron-protein complex is produced. In conclusion, by coupling iron oxidation with stepwise assembly, frataxin can successively function as an iron chaperon or an iron store. Reduced iron availability and solubility and increased oxidative damage may therefore explain the pathogenesis of FRDA. [source]