Alternative Iron Source Research Articles

Relative Availability of Iron in Mined Humic Substances for Weanling Pigs

Humic substances include several biological active and inactive compounds that are commonly used for improving soil fertility. Use of humic substances in swine diets is a novel concept. Humic substances contain 8,700 mg/kg of iron but its bioavailability is unknown. This study was conducted to test the bioavailability of iron in humic substances for nursery pigs. One hundred twenty five pigs (Newsham, Colorado Springs, CO) were not given supplemental iron while nursing for 21 d. Pigs were weaned on d 21 and allotted to one of five treatments (four control treatments with different levels of supplemented iron; 0, 30, 70 and 88 mg/kg from FeSO4 and one treatment with 70 mg/kg iron from humic substances). Pigs were fed diets for 5 wk ad libitum and water was accessible freely. Body weight and feed intake were measured weekly. Blood samples were taken from pigs on d 28 to measure the number of red blood cells and hemoglobin concentration. Pigs fed a diet with the humic substances grew faster (p 0.05). Humic substances can replace FeSO4 as an alternative iron source for pigs at 71% relative bioavailability. (Asian-Aust. J. Anim. Sci. 2004. Vol 17, No. 9 : 1266-1270)

The type Ia supernova rate in z <= 1 galaxy clusters: implications for progenitors and the source of cluster iron

The iron mass in galaxy clusters is about six times larger than could have been produced by core-collapse supernovae (SNe), assuming the stars in the cluster formed with a standard initial mass function (IMF). SNe Ia have been proposed as the alternative dominant iron source. Different SN Ia progenitor models predict different ‘delay functions’, between the formation of a stellar population and the explosion of some of its members as SNe Ia. We use our previous measurements of the cluster SN Ia rate at high redshift to constrain SN Ia progenitor models and the star-formation epoch in clusters. The low observed rate of cluster SNe Ia at z∼ 0–1 means that, if SNe Ia produced the observed amount of iron, they must have exploded at even higher z. This puts a >95 per cent upper limit on the mean SN Ia delay time of τ < 2 Gyr (< 5 Gyr) if the stars in clusters formed at zf < 2 (zf < 3), assuming H0= 70 km s−1 Mpc−1. In a companion paper, we show that, for some current versions of cosmic (field) star-formation history (SFH), observations of field SNe Ia place a lower bound on the delay time, τ > 3 Gyr. If these SFHs are confirmed, the entire range of τ will be ruled out. Cluster enrichment by core-collapse SNe from a top-heavy IMF will then remain the only viable option.

Simultaneous Synthesis of Iron Carbide and Rutile from Ilmenite Ore by Thermochemical Reactions

Simultaneous synthesis of iron carbides (mainly Fe 3 C) and rutile (TiO 2 ) from natural ilmenite ore (mainly FeTiO 3 ) were examined by thermochemical reactions with H 2 -CO or H 2 -CH 4 gas mixtures at temperatures of 1 073-1 273 K. The low sulfur pressures incapable of forming FeS was added to these gas mixtures to make stable iron carbides without free carbon. Iron carbide is currently interesting as alternative pure iron sources in steelmaking. The rutile is also available as a feedstock for titanium industry. First, partial conversion from ilmenite to rutile and metallic iron mostly proceeded and subsequently iron carbidization occurred together with further reduction of rutile. Finally, these processes with both gas mixtures provided iron carbide (Fe 3 C) and lower titanium oxides such as Magneli phases [Ti n O 2n-1 , 4≤n≤9 namely TiO 2-x ) and/or Ti 3 O 5 rather than rutile. Reaction time, H 2 /CH 4 ratio, sulfur potential, and temperature dependence of reaction behavior was examined further. The iron carbidization rates were analysed using the first order rate model. Ilmenite samples prepared from reagents showed slightly slower conversion rates to titanium oxides at 1 073 K than the natural ore ones, though both samples showed similar iron carbidization rates.

Discovery of a haem uptake system in the soil bacterium Bradyrhizobium japonicum.

In Bradyrhizobium japonicum, the nitrogen-fixing symbiont of soybeans, we have identified a haem uptake system, Hmu, that comprises a cluster of nine open reading frames. Predicted products of these genes include: HmuR, a TonB-dependent haem receptor in the outer membrane; HmuT, a periplasmic haem-binding protein; and HmuUV, an ABC transporter in the inner membrane. Furthermore, we identified homologues of ExbBD and TonB, that are required for energy transduction from the inner to the outer membrane. Mutant analysis and complementation tests indicated that HmuR and the ExbBD-TonB system, but not the HmuTUV transporter, are essential for haem uptake or haem acquisition from haemoglobin and leghaemoglobin. The TonB system seems to be specific for haem uptake as it is dispensable for siderophore uptake. Therefore, we propose the existence of a second TonB homologue functioning in the uptake of Fe-chelates. When tested on soybean host plants, hmuT-hmuR and exbD-tonB mutants exhibited wild-type symbiotic properties. Thus, haem uptake is not essential for symbiotic nitrogen fixation but it may enable B. japonicum to have access to alternative iron sources in its non-symbiotic state. Transcript analysis and expression studies with lacZ fusions showed that expression of hmuT and hmuR is induced under low iron supply. The same was observed in fur and irr mutant backgrounds although maximal induction levels were decreased. We conclude either that both regulators, Fur and Irr, independently mediate transcriptional control by iron or that a yet unknown iron regulatory system activates gene expression under iron deprivation. An A/T-rich cis-acting element, located in the promoter region of the divergently transcribed hmuTUV and hmuR genes, is possibly required for this type of iron control.

Iron bioavailability in infants from an infant cereal fortified with ferric pyrophosphate or ferrous fumarate

Infant cereals are commonly fortified with insoluble iron compounds with low relative bioavailability, such as ferric pyrophosphate, because of organoleptic changes that occur after addition of water-soluble iron sources. Our objective was to compare iron bioavailability from ferric pyrophosphate with an alternative iron source that is soluble in dilute acid, ferrous fumarate, and to evaluate the influence of ascorbic acid on iron bioavailability from ferrous fumarate in infants. Iron bioavailability was measured as the incorporation of stable iron isotopes into erythrocytes 14 d after administration of labeled test meals (25 g dry wheat and soy infant cereal, 100 g water, and 2.5 mg Fe as [57Fe]ferric pyrophosphate or [57Fe]ferrous fumarate). Ascorbic acid was added to all test meals (25 mg in study 1 or 25 or 50 mg in study 2). Infants were fed each test meal on 4 consecutive days under standardized conditions. The 2 different test meals within each study were administered 2 wk apart in a crossover design. Geometric mean iron bioavailability was significantly higher from [57Fe]ferrous fumarate than from [57Fe]ferric pyrophosphate [4.1% (range: 1.7-14.7%) compared with 1.3% (range: 0. 7-2.7%); n = 8, P = 0.008]. In this study, doubling the ascorbic acid content did not further enhance iron bioavailability; the geometric means (range) were 3.4% (1.9-6.6%) and 4.2% (1.2-18.7%) for the test meals with 25 and 50 mg ascorbic acid added, respectively (n = 9). Iron bioavailability from iron-fortified infant cereals can be improved by using an iron compound with high relative bioavailability and by ensuring adequate ascorbic acid content of the product.

Influence of several factors on synthesis of iron carbide from iron ore

Iron carbides as alternative pure iron sources were synthesised by thermochemical reactions of iron ores with H2–CO gas mixtures having low sulphur pressures incapable of forming FeS. It was proved that high quality iron carbides without free carbon can be obtained more effectively at relatively high reaction rates. Some pressurisation was effective in eliminating the detrimental influence of oxidant components in the inlet gas mixtures. Ore type, reaction time, H2 /CO ratio, sulphur potential, and total gas pressure dependencies on the iron carburisation rates were examined and the rates were analysed using a first order rate model. Comparison shows that the productivity of the proposed process should be almost one order of magnitude greater than that of a conventional Iron Carbide process.

アイアンカーバイドの基礎特性

Iron carbide has been expected as alternative iron sources for EAF steel

Assessment of alternative iron sources in the pressure leaching of zinc concentrates using a reactor model

A mathematical model is used to simulate pressure leaching of six different zinc concentrate feeds: low pyrite, high pyrite, lead-zinc concentrate blend, Red Dog concentrate, Red Dog concentrate-zinc ferrite blend and Red Dog concentrate with hot acid leach liquor. In particular, the effect of iron content of the feeds on predicted performance for a specific autoclave configuration was investigated. For the Red Dog concentrate, which does not contain enough iron for successful zinc pressure leaching, two alternative iron sources were investigated. In the first case, zinc ferrite was blended with the concentrate feed. In the second case, aqueous solution, containing ferrous and ferric sulphate, from the hot acid leaching of zinc ferrite was added to the autoclave. Simulation results are presented in terms of autogenous operation, minerals conversions, aqueous solution compositions, oxygen consumption and jarosite production.

Mobilization of ferritin iron in erythroblasts by chelating agents

Intracellular ferritin in newt ( Triturus cristatus) erythroblasts was accessible to the chelating effects of EDTA and pyridoxal phosphate. EDTA (0.5–1 mM) promoted release of radioactive iron from ferritin of pulse-labelled erythroblasts during chase incubation, but its continuous presence was not necessary for ferritin iron mobilization. Brief exposure to EDTA was sufficient to release 60–70% of ferritin 59Fe content during ensuing chase in EDTA-free medium. EDTA also suppressed cellular iron uptake and utilization for heme synthesis, but these activities were restored upon its removal. Pyridoxal-5′-phosphate (0.5–5 mM) also stimulated loss of radioactive iron from ferritin; however, ferritin iron release by pyridoxal phosphate required its continued presence. Unlike EDTA, pyridoxal phosphate did not interfere with iron uptake or its utilization for heme synthesis. Chelator-mobilized ferritin iron accumulated initially in the hemolysate as a low-molecular-weight component and appeared to be eventually released into the medium. No radioactive ferritin was found in the medium of chelator-treated cells, indicating that secretion or loss of ferritin was not responsible for decreasing cellular ferritin 59Fe content. Moreover, there was no transfer of radioactive iron between the low-molecular-weight component released into the medium and plasma transferrin. These results indicate that chelator-released ferritin iron is not available for cellular utilization in heme synthesis and that ferritin iron released by this process is not an alternative or complementary iron source for heme synthesis. Correlation of these data with effects of succinylacetone inhibition of heme synthesis and with previous studies indicates that the main role of erythroid cell ferritin is absorption and storage of excess iron not used for heme synthesis.

An improved experimental medium for freshwater toxicity studies using Daphnia magna

Some of the difficulties involved in formulating experimental media for use in toxicity studies are pointed out, with particular reference to heavy metals and their possible chelation by agents in the media. A medium suitable for Daphnia culture with the green alga, Chlorella sp., was chosen from the literature to investigate physiological responses by Daphnia to sublethal cadmium poisoning. Like most synthetic media this included the labile Fe-EDTA complex as a source of soluble iron which is shown to be essential for growth of both Daphnia and Chlorella. Attention is drawn to the almost univeral complexing ability of EDTA with metal ions, and to the mechanisms whereby EDTA may be released from the Fe-EDTA complex under experimental conditions. Synthesis of a ferri-gluconate complex as an alternative source of soluble iron is described; this complex being theoretically more iron-specific than Fe-EDTA, whilst providing equally well for Chlorella growth and Daphnia growth and fecundity. Restriction of pH variation in the experimental medium, within its chemically stable range of 6.0–9.0, is shown to be difficult over 10 days: most buffers with a suitable p K α value ( ca. 7.5) being toxic or having some complexing ability. TES buffer (p K α 7.5) and HEPES buffer (p K α 7.55) were used at various concentrations, and 0.001 M HEPES is shown to restrict pH variation to within 0.5 pH units over 10 days without adversely affecting Chlorella growth or Daphnia growth and fecundity. Chemical estimation of the degree of cadmium-complexing by each iron source and each buffer under investigation was not possible since the presence of chelating agents imposes restrictions on the methods available, particularly at low cadmium concentrations. Instead, a bioassay of the reduction in 48h acute toxicity of cadmium to Daphnia in media containing each potential chelating agent in turn is used. These data indicate that 0.001 M HEPES buffer does not complex cadmium at 0.1 ppm, and that ferri-gluconate is less likely to do so than ferri-EDTA.

An improved experimental medium for freshwater toxicity studies using Daphnia magna

Some of the difficulties involved in formulating experimental media for use in toxicity studies are pointed out, with particular reference to heavy metals and their possible chelation by agents in the media. A medium suitable for Daphnia culture with the green alga, Chlorella sp. was chosen from the literature to investigate physiological responses by Daphnia to sublethal cadmium poisoning. Like most synthetic media this included the labile Fe-EDTA complex as a source of soluble iron which is shown to be essential for growth of both Daphnia and Chlorella. Attention is drawn to the almost universal complexing ability of EDTA with metal ions, and to the mechanisms whereby EDTA may be released from the Fe-EDTA complex under experimental conditions. Synthesis of a ferri-gluconate complex as an alternative source of soluble iron is described; this complex being theoretically more iron-specific than Fe-EDTA, whilst providing equally well for Chlorella growth and Daphnia growth and fecundity. Restriction of pH variation in the experimental medium, within its chemically stable range of 6.0–9.0, is shown to be difficult over 10 days: most buffers with a suitable p K a value ( ca. 7.5) being toxic or having some complexing ability. TES buffer (p K a 7.5) and HEPES buffer (p K a 7.55) were used at various concentrations, and 0.001 M HEPES is shown to restrict pH variation to within 0.5 pH units over 10 days without adversely affecting Chlorella growth or Daphnia growth and fecundity. Chemical estimation of the degree of cadmium-complexing by each iron source and each buffer under investigation was not possible since the presence of chelating agents imposes restrictions on the methods available, particularly at low cadmium concentrations. Instead, a bioassay of the reduction in 48 h acute toxicity of cadmium to Daphnia in media containing each potential chelating agent in turn is used. These data indicate that 0.001 M HEPES buffer does not complex cadmium at 0.1 ppm, and that ferri-gluconate is less likely to do so than ferri-EDTA.