Soluble Iron Compounds Research Articles

Acidophilic heterotrophs: basic aspects and technological applications.

Acidophiles comprise a group of microorganisms adapted to live in acidic environments. Despite acidophiles are usually associated with an autotrophic metabolism, more than 80 microorganisms capable of utilizing organic matter have been isolated from natural and man-made environments. The ability to reduce soluble and insoluble iron compounds has been described for many of these species and may be harnessed to develop new or improved mining processes when oxidative bioleaching is ineffective. Similarly, as these microorganisms grow in highly acidic media and the chances of contamination are reduced by the low pH, they may be employed to implement robust fermentation processes. By conducting an extensive literature review, this work presents an updated view of basic aspects and technological applications in biomining, bioremediation, fermentation processes aimed at biopolymers production, microbial electrochemical systems, and the potential use of extremozymes.

THE INFLUENCE OF THE ANODE MATERIAL ON THE COURSE OF COMBINED PROCESSES DURING THE REGENERATION OF SULPHATE-ACID SOLUTIONS

The existing methods of regeneration of sulfo-acidic solutions, which contain iron sulfate, formed after technological operations for the preparation and etching of metal parts at metalworking enterprises are not effective and therefore are not used at Ukrainian enterprises. They are either aimed at sedimentation of the sludge of sparingly soluble iron compounds after neutralization of unreacted sulfuric acid or at dilution of the formed spent sulfo-acid solutions. The electrochemical method of regeneration of such spent sulfo-acid solutions is not properly researched. A feature of the development of technology and equipment for regeneration is a decrease in the content of iron ions and an increase in the concentration of sulfuric acid during the regeneration process. The process of electrochemical regeneration of spent steel etching solutions is characterized by a significant change in the composition of the etching solution and the temperature of the etching process. At the beginning of work, the initial solution of sulfuric acid reaches a concentration of 2.0 mol·dm-3 and does not contain iron (II) sulfate. In the process of digestion, the concentration of sulfuric acid decreases to 0.5 mol·dm-3, and the concentration of iron (II) sulfate increases accordingly. Therefore, the course of the anodic process was studied for the following solution compositions: 0.5 mol·dm-3; 1.0 mol·dm-3 and 1.5 mol·dm-3 H2SO4. Under the conditions of a decrease in the concentration of sulfuric acid, its chemical activity also decreases when interacting with iron oxides and hydroxides. An increase in the temperature of the entire process is used to increase the reactivity of the pickling solutions. The main process at the platinum anode is the release of oxygen in a wide range of current densities and a significant overvoltage of the entire process. Taking into account the obtained voltage-voltage dependences, it can be seen that the current rises when reaching potentials that significantly exceed the standard potential for obtaining oxygen from water. The advantage of the platinum anode is the slight influence of the concentration of sulfuric acid on the kinetics of the anode process. The obtained results were used for comparison with other alternative anode materials. Manganese dioxide was obtained by the method of pyrolysis of a coating solution of manganese monoacid applied to a titanium current lead, which can be represented by reaction (5) of the decomposition of manganese nitrate on a titanium plate. Due to the developed surface, the real current density was more than an order of magnitude lower on the TDMA than on the platinum anode with the same geometric dimensions. A lower current density contributed to a decrease in the steady-state potentials of oxygen release. The current density can be increased by an order of magnitude if surfactants are added to the working solution. A comparison of voltage-voltage dependences on platinum and TDMA indicates that the use of TDMA gives a more significant gain in energy consumption during the regeneration process. Taking into account that the range of current densities of 4-5 A/dm2 was determined for the cathode process according to the research results, the difference in the reduced polarization of the anode on TDMA, compared to platinum, is more than 400 mV, which will significantly reduce costs during unit operation. The use of TDMA is expedient in the galvanostatic mode of operation of the electrode unit for the process of electrochemical regeneration of spent sulfo-acid solutions of steel pickling.

The pH and medium composition impact on the efficiency of electroflotation-based extraction of slightly soluble iron, chromium and manganese compounds from water solutions and physical-chemical properties of these compounds

The study demonstrates the pH and solution ion composition impact on the average hydrodynamic diameter dm and electrokinetic potential (ζ-potential) of the dispersed phase of slightly soluble ferrous metals compounds. We examined formation dispersed phases of slightly soluble Fe (III), Cr (III), and Mn (II) compounds in the presence of OН–, CO32–, PO43– ions as precipitating agents and anionic, cationic, and non-ionic flocculating agents. The electroflotation-based extraction of slightly soluble ferrous metals compounds was found to be directly linked to dispersity and electrokinetic potential of particles, that depend on acidity and ionic medium composition. The maximal hydrodynamic diameter of dispersed phases of the slightly soluble Fe (III), Cr (III), and Mn (II) compounds were observed at isoelectric point and corresponded with pH value of the minimal dispersed phase solubility. In this case, electroflotation-based extraction was more efficient, the iron (III), manganese (II), and chromium (III) removal α reached 98, 96, and 83 %, respectively. Cationic flocculating agent additives increased the iron, manganese, and chromium extraction up to 99, 98, and 94 %, respectively. If carbonate and phosphate ions were added, the electrokinetic potential of compounds of all examined slightly soluble metals changed to negative values: –(12–19) mV in the presence of CO32– ions and –(35–43) mV in the presence of PO43– ions. This shift hindered coagulation and decreased electroflotation-based extraction of the dispersed phases, especially in case of manganese compounds (α ≤ 10%). Cationic and non-ionic flocculating agents additives balanced the high negative charge of the dispersed phases of slightly soluble ferrous metals compounds, enlarged the removal up to 98 % depending on the dispersed phase and flocculating agent. The research was conducted under financial support of the Mendeleev University of Chemical Technology of Russia within the frame of investigations on strategic development directions, project No. 3-2020-033.

Concentração de ferro e manganês em águas de abastecimento no município de Crato, Ceará: caracterização e proposta de tratamento

O objetivo desta pesquisa consiste na proposição de uma alternativa de tecnologia para a remoção de ferro e manganês em fontes de abastecimento público no município de Crato, Ceará, a partir da avaliação de parâmetros de qualidade de água atuais. A remoção desses compostos torna-se necessária haja vista os problemas associados a eles quando presentes em valores acima dos limites permissíveis. A concentração elevada provoca alterações físicas e químicas na água, como mudança de coloração e odor característico, levando a rejeição ao consumo da água. Diante disto, realizou-se análises físico-químicas em 35 pontos de abastecimento, escolhidos conforme critério de localização e existência de dados anteriores sobre sua qualidade organoléptica, a fim de identificar a concentração destes metais e propor um método compatível para sua remoção e controle eficiente. Para tanto, aplicou-se o teste de Wilcoxon, para avaliar o grau de dispersão dos dados em torno da média de concentração e em seguida ordenou os dados em faixas de concentração. A partir da análise dos resultados, foi recomendado oxidação por hipoclorito de cálcio seguida de filtração em leito de carvão ativado, por ser um dos processos mais eficientes de remoção dos compostos de ferro e manganês solúveis.

The effect of lipids, a lipid-rich ready-to-use therapeutic food, or a phytase on iron absorption from maize-based meals fortified with micronutrient powders ,

Background: Ready-to-use-therapeutic foods (RUTFs) high in lipid, protein, and iron are used to treat malnutrition. Lipids increase gastric residence time, which could increase iron absorption, particularly from poorly soluble iron compounds and in combination with phytase.Objectives: The objectives were to 1) assess the effect on iron absorption of a lipid emulsion given 20 min before or together with an iron-fortified maize meal and 2) assess iron absorption from a micronutrient powder (MNP) given with a nutrient-dense RUTF and/or a microbial phytase.Design: A total of 41 women participated in 3 studies. They consumed a maize meal fortified with isotopically labeled ferrous sulfate (FeSO4; study 1) or ferric pyrophosphate (FePP; study 2). In studies 1 and 2, a lipid emulsion was given with or 20 min before the meal. In study 3, with the use of a 2 × 2 factorial design, subjects consumed a maize meal fortified with an MNP containing labeled FeSO4 (MNP) given with an RUTF (MNP+RUTF), with a phytase (MNP+phytase), or both (MNP+RUTF+phytase). Iron absorption was assessed by isotope incorporation in erythrocytes 14 d after the test meals.Results: The lipid emulsion given either before or with the meal significantly increased iron absorption from FePP by 2.55-fold (95% CI: 1.48-, 4.37-fold; P = 0.001) but not from FeSO4 There was a trend to increase iron absorption with the MNP+RUTF meal, which did not reach significance (1.21-fold; 95% CI: 0.92-, 1.61-fold; P = 0.060). The addition of phytase to MNP and MNP+RUTF significantly increased iron absorption by 1.85-fold (95% CI: 1.49-, 2.29-fold; P < 0.001), with no interaction between phytase and RUTF.Conclusions: In iron-fortified maize-based meals, the addition of lipids more than doubles iron absorption from FePP. Our results suggest the possibility of an enhancing effect on iron absorption of lipid-rich RUTFs, but more research is needed to determine this. This trial was registered at clinicaltrials.gov as NCT01991626.

Effects of iron, manganese and zinc enriched coffee and tea wastes on lettuce – a field trial

Ensuring proper microelement supply under alkaline soil conditions could be a challenge even with the application of synthetic chelates. In this study, the application of coffee and tea wastes enriched with water soluble inorganic iron, manganese and zinc compounds was compared to water solution application of the same compounds at the same amount on a field with an alkaline Calcaric Arenosol. One butterhead and two iceberg lettuce cultivars were used as test plants. The effects of microelement enriched wastes on microelement availability in the soil, measured by DTPA-TEA method, was not clear-cut. However, the soil application of those microelement enriched wastes increased the nutritional value of lettuce by resulting in significantly higher concentration in cores for all the three investigated microelements. The highest rate of increase was observed for iron. As a consequence, lettuce heads accumulated significantly higher amount of iron, while this was not the case for manganese and zinc. There were comprehensive differences in the microelement concentration of the cores of the three investigated cultivars, with the butterhead type having especially high iron concentration. Head weights were not affected by the treatments. Hence, under the field conditions of this study, higher microelement concentration and uptake in the lettuce heads was not a prerequisite for good lettuce yield, as it was proved by the results of a zero control. However, the soil application of microelement enriched coffee and tea wastes for supplying microelements for lettuce in alkaline soil proved to be promising, especially for iron.

The Widespread of Fe(III)-Reducing Bacteria in Natural Ecosystems of Ecuador

The widespread of Fe(III)-reducing microorganisms in natural ecosystems of Ecuador of La Favorita, Tungurahua volcano and Papallacta areas was experimentally proved. High efficiency of microbial precipitation of soluble iron compounds was also demonstrated. Obtained results indicate the potential ability of Fe(III)-reducing microorganisms to influence the formation of carbon and iron vector fluxes in ecosystems, as well as development of effective biotechnologies of water purification from iron compounds.

Simultaneous Quantitation of Manganese (II) and Iron (III) In An Industrial Effluent Using Differential Pulse Polarography

In the present study, a successful attempt has been made to develop a simple method for the simultaneous determination of manganese (II) and iron (III) in an industrial effluent using differential pulse polarography (DPP) technique. Quantification of manganese (II) and iron (III) was done in Triethanolamine and KOH as a supporting electrolyte. The polarogram recorded for the industrial effluent in triethanolamine and KOH showed two peaks at -0.3V and ­0.82V vs. saturated calomel electrode which were confirmed to be of manganese (II) and iron (III) respectively by the method of standard addition. The linear working range for manganese (II) and iron (III) both was 1.408 µg/mL to 4.977 µg/mL. The proposed method was found to be simple, precise, and accurate and can be successfully applied for the analysis and simultaneous determination of manganese (II) and iron (III) in industrial effluents. Keywords: Differential pulse polarography, Industrial effluent, Iron (III), Manganese (II), Potassium hydroxide, Triethanolamine, I. Introduction Rapid industrialization and abnormal population growth has enhanced water pollution. Monitoring the metal ions and organic compounds in aquatic environment has been a subject of great concern over the last few decades and will continue to be so, as increasing number of metal ions in increasing amounts and a diverse array of organic compounds form a part of an industrial effluent. The heavy metals like Lead, Cadmium, Mercury, Arsenic, Iron, Nickel, Copper and others are used widely in industries. Thus, monitoring of these toxic substances is an integral part of environmental management. Some of these elements may be micronutrients for many living organisms and are required in small amounts for normal healthy growth, but any metal ion in large amount will always cause acute or chronic toxicity. Manganese is an essential trace mineral. The mineral is considered to be essential for the formation of healthy red blood cells, proper pituitary gland function, and the maintenance of good eyesight. Manganese is not only necessary for humans to survive, but it is also toxic when too high concentrations are present in a human body. Iron is a dietary requirement for most organisms. In small quantities, certain metals are nutritionally essential for a healthy life. These elements are also found in commercially available multivitamin products. Water soluble binary iron compounds such as FeSO4, FeCl2 may cause toxic effects with exceeding concentrations. The present paper deals with simultaneous quantitation of such electroactive species which are commonly associated with effluents from pharmaceutical industries. Potentiometric stripping analysis of simultaneous determination of metal ions has been reported

Iron and chromium sulfates from ferrochromium alloy for tanning

In this study we investigated the production of soluble iron and chromium sulfate complexes from high carbon ferrochromium alloy (Fe–Cr–HC) for utilization as a tanning agent. The temperature, sulfuric acid concentration, and the reaction time between Fe–Cr–HC and sulfuric acid were selected as independent variables for iron and chromium conversion. A quadratic response surface model was adjusted using the Box–Behnken statistical experimental design technique. The results obtained by solving multi-objective optimization problem have shown about 98.6–100% Cr and 86.9–89.1% Fe conversions. Perchloric acid and ammonium sulfate additions were investigated in order to determine the system limitations. The results have showed that an increase of perchloric acid concentration decreased the quantity of soluble chromium and iron compounds, while an ammonium sulfate addition improved the conversion of chromium up to 100%.

The influence of earthworms on the mobility of microelements in soil and their availability for plants

The influence of earthworms (Aporrectodea caliginosa, Lumbricus rubellus, L. terrestris, and Eisenia fetida) on the mobility of microelements and their availability for plants was studied. The contents of water-soluble Fe and Mn compounds extracted from the coprolites were 5–10 times higher than that in the soil (enriched in calcium carbonate and dried) consumed by the earthworms. This digestion-induced effect became higher with the age of the coprolites (up to 9 days) and took place under their alkalization. In the excreta (surface + enteric) of earthworms, the Fe concentration exceeded those of Mn and Zn by many times. Iron and manganese were mostly concentrated (>80% and >60%, respectively) in the organic part of the excrements. In the tests with hydroponics, the excreta were found to be a source of iron compounds available for plants that were similar to Fe2(SO4)3 or Fe-citrate by their physiological effect in the case when the Fe concentration in the excretions was above 0.7 μM. However, the single application of excreta of different earthworm species into the CaCO3 enriched soil did not significantly affect the plant (cucumber) nutrition. The analysis of the transport of microelements with xylem sap showed that this fact appeared to be due to the absence of an Fe deficit in the cucumber plants because of their high capability for the absorption of weakly soluble iron compounds.

Comparative Study of Femineral® and Floradix® in Women of Child-Bearing Age and Adolescent Girls with Iron Deficiency Anaemia

This double blind randomised trial compared the clinical efficacy of Femineral®, a proprietary herbal preparation containing highly soluble iron compounds, minerals, and vitamins, with Floradix®, the most popular iron supplement in Scandinavia for patients with iron deficiency anaemia (IDA). Fifty women of childbearing age and adolescent girls, all diagnosed with IDA, were randomised into two groups. One group (n = 26) was treated with Femineral (10 ml twice a day; 15 mg of iron supplement/day), while the second (n = 24) received Floradix® (10 ml twice a day; 20 mg of iron supplement/day). The efficacy of 28 days of treatment in each group was evaluated by analysis of serum iron levels, blood haemoglobin and erythrocyte counts; by the mental performance of the patients on days one and 28; and by assessment of IDA symptoms, such as pale skin colour, fatigue, irritability, weakness, constipation, brittle nails, cold hands and feet, headache, blue tinge to sclera, and feeling of well being on days one, seven, 14 and 28. The Femineral group showed significant improvements in blood haemoglobin levels and red cell counts after 28 days, while the Floradix group did not. The Femineral group showed better improvements in other IDA symptoms, such as impaired mental performance, pale skin colour, fatigue, irritability, weakness, constipation, brittle nails, cold hands and feet. Both groups showed significant improvements in serum iron levels at the end of the study. Such improvements correlate with the results of memory tests: the number of errors by both groups was significantly lower at the end of the study. There were no significant differences in memory tests between the two groups. Eight patients in the Floradix group and one in the Femineral group reported drowsiness. The Femineral group reported two other adverse events (nausea and vomiting). Femineral can be used safely in the treatment of iron deficiency anaemia. It is more efficient and safe than Floradix.

Bestimmung von Redoxzonen in einem mineralölbelasteten Grundwasserleiter

Goal and ScopeThe goal of this study is the investigation and the grafic presentation of the characteristic redox zonation in a mineral oil contaminated aquifer which will be formed in the plume downstream of the contamination source. Methanogenic conditions, sulfate-reduction, Fe(III)-reduction, Mn(IV)-reduction, nitrate-reduction, aerobic conditions. By that indications type and degree of microbial degradation which is the most important part in Natural Attenuation (NA) processes can be obtained easily.MethodsChanges of the groundwater parameters Eh, O2, NO −3 , SO4 2−, Fe2+, Mn2+, HCO3 −, Ca2+ will be measured upstream, downstream and also in the centre of the plume. The results will be presented in a sequence of special diagrams.Results and ConclusionWhen microbial degradation of hydrocarbons takes place, a microbial community will always use that electron acceptor from which it will gain a maximum of energy by the corresponding redox-reactions. This means as long as oxygen is available this will be used. After its depletion nitrate serves as electron acceptor leading via nitrite to the formation of nitrogen or ammonia. Manganese (IV) and Iron (III) species which are rather insoluble are mainly available from the soil-phase, can act as electron acceptor as next, leading to soluble Manganese (II) and Iron (II) compounds in groundwater. Finally before methanogenic conditions occur sulphate will become a suitable electron acceptor leading to the formation of hydrogen sulphide. All these processes of mineralization of the hydrocarbons will lead to the production of CO2 and as consequence to an increase of HCO3 − in groundwater changing the calcareous/carbonic acid-equilibrium. By that more soluble Ca(HCO3)2 is formed from insoluble CaCO3, so the concentration from Ca2+ will also inerease. Thus, by the action of microorganisms, a typical redox-zonation and changes of other parameters will occur.Recommendations and PerspectiveTo follow the changes in time and space of some characteristic groundwater parameters is a simple way to estimate the potential of microbial degradation in a contaminated aquifer considering Natural Attenuation (NA)-processes.

Some ecophysiological and historical approaches to species richness and calcicole/calcifuge behaviour — contribution to a debate

Species richness in vascular plants was related to the plants’ calcifuge or calcicole behaviour using documentation from forests and open-land vegetation at about one thousand sites in the southern parts of Sweden. It is concluded that vegetation of strongly acid soils (pH-KCl < 4.5) have fewer vascular plant species than comparable vegetation of other soils, whereas there are no consistent differences in species richness between slightly-moderately acid and calcareous sites. Low species richness is particularly related to high concentrations of Al3+ and H+ ions (either soil solution concentrations or concentrations of exchangeable ions), not to a lack of calcium carbonate. The majority of plant species are able to render the sparingly soluble phosphate, iron and manganese compounds of high-pH soils available, but they are unable to tolerate much Al3+ or H+. Acidicole (calcifuge) species have developed the power of tolerating Al3+ and H+, which may be considered a secondary property of plants, but they have lost the power of solubilizing critical mineral nutrients in high-pH soils. The reasons why these ecophysiological properties are inversely related in the current flora are obscure, difficult to account for experimentally and a main ecological problem. In areas with cool-temperate climates the flora was partly or mainly extinguished by the Pleistocene glaciations. Comparatively fewer calcifuge than calcicole species have, since then, had enough time to develop, and the number of calcifuges is lower, in spite of the fact that most natural and seminatural soils of these areas are nowadays acidic.

Iron Homeostasis in Plants: Sensing and Signaling Pathways

Since iron is both an essential element as well as a potential toxin, it is a nutrient which on the one hand fulfils many important functions in plants but on the other can cause severe cell damage as a consequence of the formation of reactive hydroxyl radicals. Uptake of iron, its concentrations within particular tissues, and its subcellular distribution is therefore subject to careful control. In addition, the low bioavailability of iron in most soils necessitates the mobilization of sparingly soluble iron compounds. This has led to the evolution of concerted responses that assist in maintaining an adequate supply of iron for plant roots. These responses comprise morphological changes, such as the development of extra root hairs, formation of rhizodermal transfer cells, and induction of cluster roots, as well as induction of genes coding for enzymes involved in the mobilization and uptake of nutrients. Investigations at the protein, mRNA, and structural level showed that both systemic responses, involving transmission of long distance signals, and external nutritional signals, inducing localized responses, are involved in the complex control of iron homeostasis. A number of components have been identified at the molecular level, but the interplay between these components and the signal transduction cascades leading to an iron status within an adequate range are largely unknown. This review summarizes the available data that explain how these processes are coordinated to maintain a continuous and acceptable Fe supply despite changing environmental conditions.

The usefulness of elemental iron for cereal flour fortification: a SUSTAIN Task Force report. Sharing United States Technology to Aid in the Improvement of Nutrition.

Fortification of cereal flours may be a useful public health strategy to combat iron deficiency. Cereal flours that are used shortly after production (e.g., baking flour) can be fortified with soluble iron compounds, such as ferrous sulfate, whereas the majority of flours stored for longer periods is usually fortified with elemental iron powders to avoid unacceptable sensory changes. Elemental iron powders are less well absorbed than soluble iron compounds and they vary widely in their absorption depending on manufacturing method and physicochemical characteristics. Costs vary with powder type, but elemental iron powders are generally less expensive than ferrous sulfate. This review evaluates the usefulness of the different elemental iron powders based on results from in vitro studies, rat assays, human bioavailability studies, and efficacy studies monitoring iron status in human subjects. It concludes that, at the present time, only electrolytic iron powder can be recommended as an iron fortificant. Because it is only approximately half as well absorbed as ferrous sulfate, it should be added to provide double the amount of iron.

Post-reclamation changes in estuarine mudflat sediments at Bothkennar, Grangemouth, Scotland

Abstract The Engineering &amp; Physical Sciences Research Council research site at Bothkennar is located on former intertidal mudflats adjacent to the Forth estuary, which were reclaimed for agricultural use around the year 1784. A desiccated surface crust has developed in the 200 years following the reclamation, largely in response to the introduction of artificial drainage. Its formation has involved both compaction and material translocation, due to effective stress changes and to infiltration and geochemical alteration respectively. At first, new deposits accumulated in an artificial tidal lagoon and underwent autocompaction under saturated conditions. The subsequent introduction of field drains and cultivation then induced suction stresses due to evapotranspiration, leading to overconsolidation by around 150–200 kPa. These processes have also been associated with the development of an immature soil profile to a depth of around 0.7 m. The infiltration of fresh water has caused both desalination and the eluviation of clay particles. There is also a general rise in pH and fall in Eh with depth, which is associated with leaching and the downward translocation of DCB (dithionate-citrate-bicarbonate) soluble iron compounds. We conclude that the physical development of the crust was rapid and is now largely completed, whereas the chemical development is not yet completed and thus the soil profile remains immature.

Characterizing nicotianamine aminotransferase: Improving its assay system and details of the regulation of its activity by Fe nutrition status

Under iron deficient conditions, graminaceous plants secrete mugineic acid family phytosiderophores (MAs) from their roots to dissolve sparingly soluble iron compounds in the rhizosphere, and take up iron in the form of an Fe3+-MAs complex (Takagi 1976). A good correlation has been reported between the tolerance of Fe-deficiency and the amount of secreted MAs (Takagi 1993). Therefore, by using the genes involved in MAs biosynthesis, molecular breeding might produce transgenic plants tolerant to Fe-deficiency with a high level of MAs secretion. The biosynthetic pathway of MAs from L-methionine has been clarified (Fig. 1) and the enzymes participating in this process are now being investigated to isolate the genes responsible. Nicotianamine aminotransferase (NAAT) catalyzes the amino group transfer between nicotianamine (NA) and 2-oxoglutaric acid (Fig. 1). In order to purify NAAT, enzyme assay methods for NAAT have been developed and modified (Shojima et al. 1990; Ohata et al. 1993; Kanazawa et al. 1994). Some characteristics of NAAT have been reported using these enzyme assay methods (Kanazawa et al. 1994, 1995). Here, we further investigate some characteristics of this enzyme to improve the enzyme assay method, namely 1) the effect of K+ and Mg2+ on NAAT activity in vitro, and 2) the direct influence of MAs, Fe3+, and Fe2+ on NAAT activity. In addition, based on these results, the induction of enzyme activity by Fe-deficiency and suppression of the activity by Fe-resupply was investigated, by applying the new enzyme assay method.

Analysis of soluble iron compounds in the bacterial oxidation of pyrite

Bacterial solubilization and oxidation of iron from pyrite were determined with the use of analytical methods which differentiated between total iron and reduced and oxidized forms of soluble iron. About 70% precipitation of Fe(III) was apparent in six-week old cultures. Yeast extract (0.2 and 2%) inhibited the bacterial oxidation of pyrite. Incomplete (∼50%) bacterial oxidation of iron dissolved from pyrite was attributed to the inhibition of the bacterial iron-oxidation at pH 1.2–1.3. Sample pretreatments with ion-exchange resins before analysis indicated that cationic iron concentration was almost identical with that of total iron in bacterial cultures; anionic forms of Fe amounted to about 7% of the total soluble iron.

Mechanisms of antioxidant action: Time‐controlled photoantioxidants for polyethylene based on soluble iron compounds

AbstractThe effects of two component combinations of soluble iron compounds on the rate of photooxidation and associated embrittlement times of low density polyethylene (LDPE) are examined. It is found that photoantioxidants retard the photo prooxidant effects of iron compounds giving controllable induction periods. In the case of the combination of a nickel dithiocarbamate (photoantioxidant) and an iron dithiocarbamate (photo prooxidant) a very wide range of embrittlement times can be obtained in which the induction period is controlled by the nickel complex and the post‐induction period rate by the iron complex.

Iron and zinc compounds in the muscle meats of beef, lamb, pork and chicken.

AbstractBeef, lamb, pork and chicken leg muscles were extracted with distilled water and the soluble iron and zinc compounds separated by gel filtration and dialysis. Iron was distributed between five main components: an insoluble fraction, ferritin, haemoglobin, myoglobin and a low molecular weight fraction. In beef and lamb, myoglobin was the predominant iron compound but in pork and chicken, most of the iron was associated with the insoluble fraction. Whereas more than 70% of beef iron was associated with the haemoproteins, haemoglobin and myoglobin, less than 30% of chicken iron was in this form. Even so, in all meats most of the soluble iron was associated with the haemoproteins. Zinc was present mainly in the insoluble fraction. The soluble zinc was distributed between five main components. Over 70% of soluble zinc was associated with two components having molecular weights of 65 000 and 35 000. The nature and availability of zinc and iron in the various meat fractions is discussed.