Journal articles: 'Sulfur and iron reduction'

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Rezaee, Bahram, Atefe Sarvi, Atiyeh Eslamian, Seyed MehdiJebraeeli, and Abolfazl Zabihi. "Sulfur reduction in Sangan iron ore by flotation." E3S Web of Conferences 18 (2017): 01023. http://dx.doi.org/10.1051/e3sconf/20171801023.

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in this study the flotation of pyrite as the main sulfide impurity of Sangan iron ore in Iran, was investigated. For this purpose the effect of collector type, pH, collector concentration and stage dosing on reverse flotation of iron sulfide ore from magnetite ore was investigated. Two type of thiol collectors include xanthates (sodium isopropyl xanthate (SIPX) and potassium amyl xanthate (PAX)) and dithiocarbamate (di-ethyl dithiocarbamate (DTC)) and the mixture of collectors was studied. The highest sulfur removal was obtained with potassium amyl xanthate. Stage dosing had a significant effect in sulfide flotation and the best recovery was obtained when the collector was added in 4 stages. The acidity had a positive effect on sulfide floatability and the best result was obtained at pH 3.5-4. Investigation about collector concentration showed that increasing the SIPX concentration enhanced the sulfur removal but this factor was not effective for PAX.

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Cammack, Richard. "Iron–sulfur proteins." Biochemist 34, no. 5 (October 1, 2012): 14–17. http://dx.doi.org/10.1042/bio03405014.

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Iron makes up 35% of the Earth's mass, and is plentiful in its crust (approximately 5%), so it is not surprising that Biology has found many different applications for it. Iron–sulfur (Fe–S) clusters are essential, ubiquitous inorganic cofactors in electron-transport proteins of respiration and photosynthesis, and are responsible for the activity of hundreds of enzymes1. Various types of clusters (Figure 1) occur in iron-sulfur proteins, bound covalently to protein ligands, usually cysteine sulfur. Their activity is not confined to oxidation/reduction; in enzymes such as aconitase, they are involved in substrate binding and conversion. Fe–S enzymes that catalyse difficult reactions, such as nitrogenase in nitrogen fixation and hydrogenase in hydrogen production, contain complex ‘superclusters’2.

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Straub, Kristina L., and Bernhard Schink. "Ferrihydrite-Dependent Growth of Sulfurospirillum deleyianum through Electron Transfer via Sulfur Cycling." Applied and Environmental Microbiology 70, no. 10 (October 2004): 5744–49. http://dx.doi.org/10.1128/aem.70.10.5744-5749.2004.

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ABSTRACT Observations in enrichment cultures of ferric iron-reducing bacteria indicated that ferrihydrite was reduced to ferrous iron minerals via sulfur cycling with sulfide as the reductant. Ferric iron reduction via sulfur cycling was investigated in more detail with Sulfurospirillum deleyianum, which can utilize sulfur or thiosulfate as an electron acceptor. In the presence of cysteine (0.5 or 2 mM) as the sole sulfur source, no (microbial) reduction of ferrihydrite or ferric citrate was observed, indicating that S. deleyianum is unable to use ferric iron as an immediate electron acceptor. However, with thiosulfate at a low concentration (0.05 mM), growth with ferrihydrite (6 mM) was possible and sulfur was cycled up to 60 times. Also, spatially distant ferrihydrite in agar cultures was reduced via diffusible sulfur species. Due to the low concentrations of thiosulfate, S. deleyianum produced only small amounts of sulfide. Obviously, sulfide delivered electrons to ferrihydrite with no or only little precipitation of black iron sulfides. Ferrous iron and oxidized sulfur species were produced instead, and the latter served again as the electron acceptor. These oxidized sulfur species have not yet been identified. However, sulfate and sulfite cannot be major products of ferrihydrite-dependent sulfide oxidation, since neither compound can serve as an electron acceptor for S. deleyianum. Instead, sulfur (elemental S or polysulfides) and/or thiosulfate as oxidized products could complete a sulfur cycle-mediated reduction of ferrihydrite.

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Zhang, Rui Yong, Sabrina Hedrich, and Axel Schippers. "Reduction of Iron(III) Ions at Elevated Pressure by Acidophilic Microorganisms." Solid State Phenomena 262 (August 2017): 88–92. http://dx.doi.org/10.4028/www.scientific.net/ssp.262.88.

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A composed mixed acidophilic, iron-oxidizing culture (FIGB) and a thermo-acidophilic enrichment culture (TK65) were used to evaluate microbial iron(III) reduction coupled to oxidation of reduced inorganic sulfur compounds (RISCs) under high pressure. Experiments were done in batch culture in high pressure vessels at 1 and 100 bar. Microbial abundance and activity were determined by measuring iron(II) concentration, direct cell counting, T-RFLP and quantitative real-time PCR. The data indicate that both cultures are able to reduce soluble iron(III) by oxidation of sulfur compounds under anaerobic conditions. At high pressure (100 bar) these acidophiles were capable of growing and microbial ferric iron reduction was only partially inhibited. These results indicate that acidophiles can be barotolerant and their activities are contributing to sulfur and iron cycling in anaerobic environments including deep ore deposits which is highly relevant for in situ leaching operations.

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Zulhan, Zulfiadi, Zhahrina Adzana, Mona Munawaroh, Achmad Haerul Yusro, Jonathan Dwiputra Christian, Aura Dwi Saputri, and Taufiq Hidayat. "Sulfur Removal and Iron Extraction from Natrojarosite Residue of Laterite Nickel Ore Processing by Reduction Roasting." Metals 13, no. 1 (December 24, 2022): 52. http://dx.doi.org/10.3390/met13010052.

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An alternative laterite nickel ore processing using sulfuric acid as a leaching agent to produce class 1 nickel as a raw material for electric vehicle batteries produces natrojarosite residue as a by-product during the precipitation of iron and aluminum step. The natrojarosite residue contained iron and high sulfur, which is challenging to utilize as an iron source for steel manufacturing since sulfur can contaminate the steel product. This study focuses on sulfur elimination and iron extraction from natrojarosite. The natrojarosite was roasted for sulfur removal isothermally at different temperatures ranging from 500 until 1100 °C for 4 h. Roasting at 1100 °C resulted a decrease in sulfur content from 12.18% to 3.81% and an increase in iron content from 16.23% to 28.54%. The sulfur released during roasting can, in principle, be recirculated to a sulfuric acid plant and reused as a leaching agent in the nickel ore processing plant. The unroasted and roasted natrojarosite residues were then reduced by coconut shell charcoal in the temperature range of 1000–1400 °C. The results showed that the metallic iron could be obtained from both unroasted and roasted natrojarosite residue at a temperature of 1200 °C and higher. The sulfur content in the oxide phase of unroasted natrojarosite residue was significantly higher than roasted natrojarosite residue. However, the roasting did not significantly influence the sulfur content in the metal phase. The sulfur content in the metal phase from unroasted and roasted natrojarosite residue was less than 1.2%. This result indicated that the removal of sulfur and metal oxide reduction in the natrojarosite residue could be carried out simultaneously in one stage where the natrojarosite residue is reduced by carbonaceous material at a temperature of 1200 °C or higher.

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Kupka, Daniel, Mark Dopson, and Olli H. Tuovinen. "Sulfur Oxidation and Coupled Iron Reduction at Low Temperatures." Advanced Materials Research 20-21 (July 2007): 584. http://dx.doi.org/10.4028/www.scientific.net/amr.20-21.584.

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The purpose of this work was to characterize elemental sulfur oxidation by a psychrotrophic Acidithiobacillus ferrooxidans culture that originated from an AMD-impacted surface soil in a permafrost area in northern Siberia. In this work, the iron-oxidizing culture was cultivated with elemental sulfur with and without Fe2+ or Fe3+ in flasks on a shaker to avoid oxygen limitation.

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Deng, Jiu Shuai, Shu Ming Wen, Shao Jun Bai, Mei Fang Xie, and Hai Ying Shen. "Sulfur Content Reduction and Iron Grade Improvement of V-Ti Magnetite Concentrate by Combining Reverse Flotation and Magnetic Separation." Advanced Materials Research 524-527 (May 2012): 1115–23. http://dx.doi.org/10.4028/www.scientific.net/amr.524-527.1115.

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For low-grade iron ore, smelting costs and resource wastage will be increased. Product quality of such ore is affected adversely by an excessive amount of sulfur. This also causes environmental pollution. In accordance with the vanadium-titanium (V-Ti) magnetite concentrate properties with low iron grade and high sulfur content, the joint process of magnetic separation and flotation was carried out. Magnetic separation was conducted to increase the iron grade, while reverse flotation was used to reduce sulfur content. Results show that the feeding mainly contains titanomagnetite, hematite, and pyrite. The sulfur was primarily found in pyrite. The separation effect was influenced by the grinding fineness, magnetic intensity, collector type and dosage, and pH value. At a grinding fineness of −45 μm accounting for 87%, most of the iron minerals exhibited monomer dissociation. An open-circuit experiment was carried out under the best conditions of magnetic intensity, as well as collector and modifier dosage. Good experimental results were obtained as follows: the iron grade increased to 57.17%, iron recovery was 89.94%, sulfur content decreased from 0.66% to 0.26%, reverse flotation of sulfur foam concentrate contained almost 15.68% sulfur, the upgrade ratio was about 23, and the cobalt in the sulfur concentrate was enriched 20-fold. A method for improving the comprehensive utilization level and effect of mineral resources is provided in this study.

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Rezaee, Bahram, Atefe Sarvi, Atiyeh Eslamian, Seyed MehdiJebraeeli, and Abolfazl Zabihi. "Sulfur reduction in Sangan iron ore by flotation." E3S Web of Conferences 18 (2017): 01023. http://dx.doi.org/10.1051/e3sconf/201712301023.

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9

Flynn, T. M., E. J. O'Loughlin, B. Mishra, T. J. DiChristina, and K. M. Kemner. "Sulfur-mediated electron shuttling during bacterial iron reduction." Science 344, no. 6187 (May 1, 2014): 1039–42. http://dx.doi.org/10.1126/science.1252066.

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Li, Zhengyao, Jinzhi Wei, Na Liu, Tichang Sun, and Xuewen Wang. "Effect and Mechanism of CaO on Iron Recovery and Desulfurization by Reduction Roasting-Magnetic Separation of High-Sulfur Cyanide Tailings." Minerals 12, no. 2 (February 12, 2022): 239. http://dx.doi.org/10.3390/min12020239.

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The increasing demand for iron ore in the world causes the continuous exhaustion of mineral resources. The utilization of iron in secondary resources has become of focus. The present study was carried out to recover iron from high-sulfur cyanide tailings by coal-based reduction roasting-magnetic separation. The mechanism of CaO to increase iron recovery and reduce sulfur was investigated by observing CO and CO2 gas composition produced by the reaction, mineral composition and microstructure, distribution characteristics of sulfur, and the intercalation relationship between iron particles and gangue minerals. The results showed that the addition of CaO could increase the gasification rate of the reducing agent, increase the amount of CO2 gas produced, promote the reduction of iron minerals, and improve the metallization degree of iron. When CaO was not added, sulfur was mainly transformed into troilite, which was closely connected with iron particles and was difficult to remove by grinding and magnetic separation. With the addition of CaO, CaO preferentially formed oldhamite with active sulfur, which reduced the formation of troilite. Oldhamite was basically distributed in an independent gangue structure. There was a clear boundary between iron particles and gangue minerals. Oldhamite could be removed by grinding-magnetic separation.

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Alenezi, Khalaf M., and Hamed Alshammari. "Electrocatalytic Production of Hydrogen Using Iron Sulfur Cluster." International Journal of Chemistry 9, no. 2 (March 27, 2017): 52. http://dx.doi.org/10.5539/ijc.v9n2p52.

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In response to the energy crisis, rising fossil fuel costs and global climate warming, this study focuses on the electrocatalytic reduction of proton into hydrogen using an iron sulfur cluster in the presence of pentafluorothiophenol. The direct reduction of pentafluorothiophenol at vitreous carbon electrode occurs at Ep-1.3 V vs Ag/AgCl in Tetrabutylammonium tetrafluoroborate [Bu4N][BF4]-DMF solution. Interestingly, in the presence of Iron Sulfur Cluster [Fe4S4(SPh)4][Bu4N]2, the reduction potential shifts significantly to -0.98 V vs Ag/AgCl. Based on gas chromatography analysis, the formation of H2 has been confirmed with a current efficiency of ca. 63% after two hours, while the chemical yield at the carbon electrode was about 46%. On the other hand, no H2 gas was detected without catalyst. Importantly, the increment of the concentration of acid (up to 18 equivalents) led to a positive shifting in the reduction potential until a value of 0.18 V. These results reflect the exquisite electrocatalytic efficiency of the protein-like iron sulfur cluster in Hydrogen Evolution Reaction (HER).

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Lohmayer, Regina, Andreas Kappler, Tina Lösekann-Behrens, and Britta Planer-Friedrich. "Sulfur Species as Redox Partners and Electron Shuttles for Ferrihydrite Reduction by Sulfurospirillum deleyianum." Applied and Environmental Microbiology 80, no. 10 (March 14, 2014): 3141–49. http://dx.doi.org/10.1128/aem.04220-13.

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ABSTRACTIron(III) (oxyhydr)oxides can represent the dominant microbial electron acceptors under anoxic conditions in many aquatic environments, which makes understanding the mechanisms and processes regulating their dissolution and transformation particularly important. In a previous laboratory-based study, it has been shown that 0.05 mM thiosulfate can reduce 6 mM ferrihydrite indirectly via enzymatic reduction of thiosulfate to sulfide by the sulfur-reducing bacteriumSulfurospirillum deleyianum, followed by abiotic reduction of ferrihydrite coupled to reoxidation of sulfide. Thiosulfate, elemental sulfur, and polysulfides were proposed as reoxidized sulfur species functioning as electron shuttles. However, the exact electron transfer pathway remained unknown. Here, we present a detailed analysis of the sulfur species involved. Apart from thiosulfate, substoichiometric amounts of sulfite, tetrathionate, sulfide, or polysulfides also initiated ferrihydrite reduction. The portion of thiosulfate produced during abiotic ferrihydrite-dependent reoxidation of sulfide was about 10% of the total sulfur at maximum. The main abiotic oxidation product was elemental sulfur attached to the iron mineral surface, which indicates that direct contact between microorganisms and ferrihydrite is necessary to maintain the iron reduction process. Polysulfides were not detected in the liquid phase. Minor amounts were found associated either with microorganisms or the mineral phase. The abiotic oxidation of sulfide in the reaction with ferrihydrite was identified as rate determining. Cysteine, added as a sulfur source and a reducing agent, also led to abiotic ferrihydrite reduction and therefore should be eliminated when sulfur redox reactions are investigated. Overall, we could demonstrate the large impact of intermediate sulfur species on biogeochemical iron transformations.

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Sim, Min Sub, Shuhei Ono, and Tanja Bosak. "Effects of Iron and Nitrogen Limitation on Sulfur Isotope Fractionation during Microbial Sulfate Reduction." Applied and Environmental Microbiology 78, no. 23 (September 21, 2012): 8368–76. http://dx.doi.org/10.1128/aem.01842-12.

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ABSTRACTSulfate-reducing microbes utilize sulfate as an electron acceptor and produce sulfide that is depleted in heavy isotopes of sulfur relative to sulfate. Thus, the distribution of sulfur isotopes in sediments can trace microbial sulfate reduction (MSR), and it also has the potential to reflect the physiology of sulfate-reducing microbes. This study investigates the relationship between the availability of iron and reduced nitrogen and the magnitude of S-isotope fractionation during MSR by a marine sulfate-reducing bacterium, DMSS-1, aDesulfovibriospecies, isolated from salt marsh in Cape Cod, MA. Submicromolar levels of iron increase sulfur isotope fractionation by about 50% relative to iron-replete cultures of DMSS-1. Iron-limited cultures also exhibit decreased cytochromec-to-total protein ratios and cell-specific sulfate reduction rates (csSRR), implying changes in the electron transport chain that couples carbon and sulfur metabolisms. When DMSS-1 fixes nitrogen in ammonium-deficient medium, it also produces larger fractionation, but it occurs at faster csSRRs than in the ammonium-replete control cultures. The energy and reducing power required for nitrogen fixation may be responsible for the reverse trend between S-isotope fractionation and csSRR in this case. Iron deficiency and nitrogen fixation by sulfate-reducing microbes may lead to the large observed S-isotope effects in some euxinic basins and various anoxic sediments.

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Shang, He, Jian Kang Wen, Biao Wu, and Xiao Lan Mo. "Study on Bioleaching of Sulfur in Iron Ore by Mixed Culture." Advanced Materials Research 1130 (November 2015): 371–74. http://dx.doi.org/10.4028/www.scientific.net/amr.1130.371.

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Iron ore is the raw material for steel production, in addition to iron and slag major component, still contains sulfur and phosphorus compounds and other harmful elements, is the potential adverse effects of factors constitute the steel product quality and environment. Sulfur in iron ores into the steel products will not only produce "heat brittle" phenomenon, but also in the sintering process by roasting produce sulfur dioxide into the air, causing damage to the atmosphere and ecological environment. A typical of the high sulfur iron ore from Inner Mongolia, China, iron grade of 53.06% and sulfur content is 2.76%, the main metal mineral in the ore is magnetite, followed by magnetic pyrite, pyrite and siderite, otherwise a small amount of copper mineral chalcopyrite, bornite. In this work, a mixed culture composed by Sulfobacillus thermotolerans, Leptospirillum ferriphilum and Ferroplasma acidiphilum was used to leach the sulfur in iron ore samples, we investigated the leaching rate of sulfur under different initial pH, temperature and pulp density conditions. The results showed that under the condition of the initial pH of 1.8, the temperature was 33 °C, and pulp density 15%, after 7 days of oxidation, we got a yield of 80.16% product in which iron grade of 62.31% and sulfur content is 0.17%. Compared with original sample, sulfur content decreased 95.06%, iron grade increased by 9.25%, and iron recovery was 94.13%. From the results it can be concluded that this microbial process for high sulfur iron ore lead to a significant effect of sulfur reduction and substantial increase in iron grade.

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Sugio, Tsuyoshi, Taher M. Taha, Atsunori Negishi, and Fumiaki Takeuchi. "Existence of Ferrous Iron-Dependent Mercury Reducing Enzyme System in Sulfur-Grown A. Ferrooxidans MON-1 Cells." Advanced Materials Research 71-73 (May 2009): 745–48. http://dx.doi.org/10.4028/www.scientific.net/amr.71-73.745.

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Iron-grown Acidithiobacillus ferrooxidans MON-1 cells are highly resistant to organomercurial compounds as well as mercuric chloride (HgCl2). Existence of a novel Hg2+-reducing enzyme system, in which mercury resistant aa3-type cytochrome c oxidase catalyzes the reduction of Hg2+ with reduced mammalian cytochrome c or Fe2+ as an electron donor to give Hg0, has been shown in iron-grown MON-1 cells. There has been no reports on the mechanism of Hg2+ reduction by sulfur-grown A. ferrooxidans cells. The level of mercury resistance in sulfur-grown A. ferrooxidans MON-1 cells was compared with that of iron-grown MON-1 cells. Strain MON-1 was able to grow in 1% elemental sulfur medium (pH 2.5) containing 10 μM of Hg2+ or 0.2 μM phenylmercury acetate (PMA), suggesting that the levels of mercury resistance to inorganic and organic mercurial compounds are nearly the same in iron- and sulfur-grown MON-1 cells. Activity levels of Hg0 volatilization from HgCl2, PMA, and methylmercury chloride (MMC) were also nearly the same in iron- and sulfur-grown cells and these activities were markedly activated by 100 mM of Fe2+, but strongly inhibited by 1 mM of sodium cyanide, indicating that sulfur-grown MON-1 cells has the activity of ferrous iron-dependent mercury reducing enzyme system containing aa3-type cytochrome oxidase. aa3-type cytochrome c oxidase purified partially from sulfur-grown MON-1 cells showed both the iron oxidase and mercury reductase activities in the presence, but not in the absence, of rusticyanin and c-type cytochromes (Cyc1 and Cyc2) partially purified from iron-grown MON-1 cells.

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Bao, Peng, and Guo-Xiang Li. "Sulfur-Driven Iron Reduction Coupled to Anaerobic Ammonium Oxidation." Environmental Science & Technology 51, no. 12 (June 12, 2017): 6691–98. http://dx.doi.org/10.1021/acs.est.6b05971.

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Kucera, Jiri, Eva Pakostova, Oldrich Janiczek, and Martin Mandl. "Changes in Acidithiobacillus ferrooxidans Ability to Reduce Ferric Iron by Elemental Sulfur." Advanced Materials Research 1130 (November 2015): 97–100. http://dx.doi.org/10.4028/www.scientific.net/amr.1130.97.

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Ferric iron may act as a thermodynamically favourable electron acceptor during elemental sulfur oxidation byAcidithiobacillus ferrooxidansin extremely acidic anoxic environments. A loss of anaerobic ferric iron reduction ability has been observed in ferrous iron-grownA. ferrooxidansCCM 4253 after aerobic passaging on elemental sulfur. In this study, iron-oxidising cells aerobically adapted from ferrous iron to elemental sulfur were still able to anaerobically reduce ferric iron, however, following aerobic passage on elemental sulfur it could not. Preliminary quantitative proteomic analysis of whole cell lysates of the passage that lost anaerobic ferric iron-reducing activity resulted in 150 repressed protein spots in comparison with the antecedent culture, which retained the activity. Identification of selected protein spots by tandem mass spectrometry revealed physiologically important proteins including rusticyanin and outer-membrane cytochrome Cyc2, which are involved in iron oxidation. Other proteins were associated with sulfur metabolism such as sulfide-quinone reductase and proteins encoded by the thiosulfate dehydrogenase and heterodisulfide reductase complex operons. Furthermore, proteomic analysis identified proteins directly related to anaerobiosis. The results indicate the importance of iron-oxidising system components for anaerobic sulfur oxidation in the studied microbial strain.

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Mao, Jing, Dedong He, Yutong Zhao, Lei Zhang, and Yongming Luo. "Sulfur-resistance iron catalyst in sulfur-containing VOCs abatement modulated through H2 reduction." Applied Surface Science 584 (May 2022): 152631. http://dx.doi.org/10.1016/j.apsusc.2022.152631.

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Kang, Wonchull, Chi Chung Lee, Andrew J. Jasniewski, Markus W. Ribbe, and Yilin Hu. "Structural evidence for a dynamic metallocofactor during N2 reduction by Mo-nitrogenase." Science 368, no. 6497 (June 18, 2020): 1381–85. http://dx.doi.org/10.1126/science.aaz6748.

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The enzyme nitrogenase uses a suite of complex metallocofactors to reduce dinitrogen (N2) to ammonia. Mechanistic details of this reaction remain sparse. We report a 1.83-angstrom crystal structure of the nitrogenase molybdenum-iron (MoFe) protein captured under physiological N2 turnover conditions. This structure reveals asymmetric displacements of the cofactor belt sulfurs (S2B or S3A and S5A) with distinct dinitrogen species in the two αβ dimers of the protein. The sulfur-displaced sites are distinct in the ability of protein ligands to donate protons to the bound dinitrogen species, as well as the elongation of either the Mo–O5 (carboxyl) or Mo–O7 (hydroxyl) distance that switches the Mo-homocitrate ligation from bidentate to monodentate. These results highlight the dynamic nature of the cofactor during catalysis and provide evidence for participation of all belt-sulfur sites in this process.

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Clarkson, Sonya M., Elizabeth C. Newcomer, Everett G. Young, and Michael W. W. Adams. "The Elemental Sulfur-Responsive Protein (SipA) from the Hyperthermophilic Archaeon Pyrococcus furiosus Is Regulated by Sulfide in an Iron-Dependent Manner." Journal of Bacteriology 192, no. 21 (August 27, 2010): 5841–43. http://dx.doi.org/10.1128/jb.00660-10.

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ABSTRACT The gene (sipA) encoding the sulfur-induced protein A (PF2025) is highly upregulated during growth of Pyrococcus furiosus on elemental sulfur (S0). Expression of sipA is regulated by sulfide, the product of S0 reduction, but in an iron-dependent manner. SipA is proposed to play a role in intracellular iron sulfide detoxification.

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Hedrich, Sabrina, Chris du Plessis, Nelson Mora, and D. Barrie Johnson. "Reduction and Complexation of Copper in a Novel Bioreduction System Developed to Recover Base Metals from Mine Process Waters." Advanced Materials Research 825 (October 2013): 483–86. http://dx.doi.org/10.4028/www.scientific.net/amr.825.483.

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An integrated bio-processing scheme was devised and tested in the laboratory for recovering copper, or other base metals, from pregnant leach solutions (PLS) using a two-step process involving both iron-reduction, and sulfate-reduction for H2S generation and sulfide precipitation, as a potential alternative to conventional SX-EW. Reduction of ferric iron in the PLS was achieved using iron-reducingAcidithiobacillusspp. andSulfobacillus thermosulfidooxidansin column reactors containing elemental sulfur as electron donor. Analysis of the column reactor effluents showed not only that most of the ferric iron was reduced to ferrous, but also that all of the copper (II) had been reduced to copper (I), i.e. cuprous copper. This copper (I) appeared to be complexed as it was not oxidized when exposed to ferric iron nor precipitated as a copper-sulfide when exposed to either sodium sulfide or H2S. The data suggested that copper (II) was reduced and the resulting copper (I) complexed, with both reactions probably mediated by sulfur oxy-anions produced indirectly by the bacteria, in the anoxic sulfur column bioreactors. It was also noted that copper (I) produced chemically by reduction of copper (II) by hydroxylamine was more toxic to axenic cultures ofAcidithiobacillusspp. andSb. thermosulfidooxidansthan was the copper (I) in the column effluent liquors.

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Yamamoto-Ikemoto, Ryoko, Saburo Matsui, Tomoaki Komori, and Edja Kofi Bosque-Hamilton. "Control of filamentous bulking and interactions among sulfur oxidation-reduction and iron oxidation-reduction in activated sludge using an iron coagulant." Water Science and Technology 38, no. 8-9 (October 1, 1998): 9–17. http://dx.doi.org/10.2166/wst.1998.0785.

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The effect of iron coagulant on control of filamentous bulking and phosphate removal was investigated using a laboratory scale activated sludge process. Sulfate reduction was correlated to activated sludge bulking. When FeCl2 was added to the aeration tank, most of the phosphate was removed. Sulfate reduction and filamentous bulking were also suppressed. The addition of FeCl2 was also effective in suppressing phosphate release and sulfide production from wasted sludge. Interactions among sulfur oxidation-reduction and iron oxidation-reduction were examined in the batch experiments. When FeCl2 was added, iron reducing bacteria outcompeted sulfate reducing bacteria and iron oxidizing bacteria grew predominantly.

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Mustafa, Sayaf, Liqun Luo, Botao Zheng, Chenxi Wei, and Niyonzima Christophe. "Mineralogical and Chemical Changes after Reduction Roasting of Xinjiang Iron Ore, China." Metals 12, no. 2 (January 19, 2022): 182. http://dx.doi.org/10.3390/met12020182.

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The mineralogical and chemical changes in Chinese Xinjiang iron ore containing impurities, lead, and zinc as a result of reduction roasting were studied via chemical analysis, optical microscopy, X-ray fluorescence (XRF), electron probe microanalysis (EPMA), and energy-dispersive spectroscopy (EDS). Analysis showed that hematite was the main iron-bearing mineral, with small amounts of magnetite and iron silicate; lead impurities were mainly lead oxide and lead–iron alum, while zinc oxide was the main zinc impurity. X-ray fluorescence analysis for raw samples indicated the presence of quartz, hematite, magnetite, chlorite, calcite, and dolomite. The results of the analysis of roasted samples showed an increase in hematite at temperatures of 750 °C and 950 °C, while the elemental iron increased at a temperature of 1200 °C, along with the conversion of galena to lead oxide and sphalerite to zinc oxide, with a stable quartz ratio. The chemical analysis of the raw sample showed that the TFe grade of the sample was 47.04%, while the contents of harmful Pb and Zn impurities were 0.39% and 0.30%, respectively, both of which exceed the index (less than 0.10%) required by the iron industry for raw materials. The content of harmful sulfur impurities was also high, at 1.19%, which needs to be eliminated or reduced. The results of EPMA and EDS analysis of pre-roasting raw samples showed that chemical compositions vary in different locations in the hematite, magnetite, sphalerite, and galena micro-zones. It has also been observed that quartz is mostly diffused with magnetite and hematite, and sulfur appears in small quantities in most regions. The analysis after roasting showed that the percentages of lead, zinc, and sulfur impurities decreased by a large rate. It is clear that the roasting process plays a major role in removing impurities such as sulfur, which appears in a small percentage after the roasting process, and also helps in oxidizing the impurities of lead and zinc, which helps in removing them.

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Feinberg, Lawrence F., R. Srikanth, Richard W. Vachet, and James F. Holden. "Constraints on Anaerobic Respiration in the Hyperthermophilic Archaea Pyrobaculum islandicum and Pyrobaculum aerophilum." Applied and Environmental Microbiology 74, no. 2 (November 26, 2007): 396–402. http://dx.doi.org/10.1128/aem.02033-07.

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ABSTRACT Pyrobaculum islandicum uses iron, thiosulfate, and elemental sulfur for anaerobic respiration, while Pyrobaculum aerophilum uses iron and nitrate; however, the constraints on these processes and their physiological mechanisms for iron and sulfur reduction are not well understood. Growth rates on sulfur compounds are highest at pH 5 to 6 and highly reduced (<−420-mV) conditions, while growth rates on nitrate and iron are highest at pH 7 to 9 and more-oxidized (>−210-mV) conditions. Growth on iron expands the known pH range of growth for both organisms. P. islandicum differs from P. aerophilum in that it requires direct contact with insoluble iron oxide for growth, it did not produce any extracellular compounds when grown on insoluble iron, and it lacked 2,6-anthrahydroquinone disulfonate oxidase activity. Furthermore, iron reduction in P. islandicum appears to be completely independent of c-type cytochromes. Like that in P. aerophilum, NADH-dependent ferric reductase activity in P. islandicum increased significantly in iron-grown cultures relative to that in non-iron-grown cultures. Proteomic analyses showed that there were significant increases in the amounts of a putative membrane-bound thiosulfate reductase in P. islandicum cultures grown on thiosulfate relative to those in cultures grown on iron and elemental sulfur. This is the first evidence of this enzyme being used in either a hyperthermophile or an archaeon. Pyrobaculum arsenaticum and Pyrobaculum calidifontis also grew on Fe(III) citrate and insoluble iron oxide, but only P. arsenaticum could grow on insoluble iron without direct contact.

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Rodrı́guez-Manzaneque, Marı́a Teresa, Jordi Tamarit, Gemma Bellı́, Joaquim Ros, and Enrique Herrero. "Grx5 Is a Mitochondrial Glutaredoxin Required for the Activity of Iron/Sulfur Enzymes." Molecular Biology of the Cell 13, no. 4 (April 2002): 1109–21. http://dx.doi.org/10.1091/mbc.01-10-0517.

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Yeast cells contain a family of three monothiol glutaredoxins: Grx3, 4, and 5. Absence of Grx5 leads to constitutive oxidative damage, exacerbating that caused by external oxidants. Phenotypic defects associated with the absence of Grx5 are suppressed by overexpression ofSSQ1 and ISA2, two genes involved in the synthesis and assembly of iron/sulfur clusters into proteins. Grx5 localizes at the mitochondrial matrix, like other proteins involved in the synthesis of these clusters, and the mature form lacks the first 29 amino acids of the translation product. Absence of Grx5 causes: 1) iron accumulation in the cell, which in turn could promote oxidative damage, and 2) inactivation of enzymes requiring iron/sulfur clusters for their activity. Reduction of iron levels in grx5 null mutants does not restore the activity of iron/sulfur enzymes, and cell growth defects are not suppressed in anaerobiosis or in the presence of disulfide reductants. Hence, Grx5 forms part of the mitochondrial machinery involved in the synthesis and assembly of iron/sulfur centers.

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Osorio, Héctor, Stefanie Mangold, Yann Denis, Ivan Ñancucheo, Mario Esparza, D. Barrie Johnson, Violaine Bonnefoy, Mark Dopson, and David S. Holmes. "Anaerobic Sulfur Metabolism Coupled to Dissimilatory Iron Reduction in the Extremophile Acidithiobacillus ferrooxidans." Applied and Environmental Microbiology 79, no. 7 (January 25, 2013): 2172–81. http://dx.doi.org/10.1128/aem.03057-12.

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ABSTRACTGene transcription (microarrays) and protein levels (proteomics) were compared in cultures of the acidophilic chemolithotrophAcidithiobacillus ferrooxidansgrown on elemental sulfur as the electron donor under aerobic and anaerobic conditions, using either molecular oxygen or ferric iron as the electron acceptor, respectively. No evidence supporting the role of either tetrathionate hydrolase or arsenic reductase in mediating the transfer of electrons to ferric iron (as suggested by previous studies) was obtained. In addition, no novel ferric iron reductase was identified. However, data suggested that sulfur was disproportionated under anaerobic conditions, forming hydrogen sulfide via sulfur reductase and sulfate via heterodisulfide reductase and ATP sulfurylase. Supporting physiological evidence for H2S production came from the observation that soluble Cu2+included in anaerobically incubated cultures was precipitated (seemingly as CuS). Since H2S reduces ferric iron to ferrous in acidic medium, its production under anaerobic conditions indicates that anaerobic iron reduction is mediated, at least in part, by an indirect mechanism. Evidence was obtained for an alternative model implicating the transfer of electrons from S0to Fe3+via a respiratory chain that includes abc1complex and a cytochromec. Central carbon pathways were upregulated under aerobic conditions, correlating with higher growth rates, while many Calvin-Benson-Bassham cycle components were upregulated during anaerobic growth, probably as a result of more limited access to carbon dioxide. These results are important for understanding the role ofA. ferrooxidansin environmental biogeochemical metal cycling and in industrial bioleaching operations.

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Maniou, Filippa S., Dimitris L. Bouranis, Yannis E. Ventouris, and Styliani N. Chorianopoulou. "Phenotypic Acclimation of Maize Plants Grown under S Deprivation and Implications to Sulfur and Iron Allocation Dynamics." Plants 11, no. 5 (March 6, 2022): 703. http://dx.doi.org/10.3390/plants11050703.

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The aim of this work was to study maize root phenotype under sulfur deficiency stress towards revealing potential correlations between the altered phenotypic traits and the corresponding dry mass, sulfur, and iron allocation within plants at the whole-plant level. The dynamics of root morphological and anatomical traits were monitored. These traits were then correlated with plant foliage traits along with dry mass and sulfur and iron allocation dynamics in the shoot versus root. Plants grown under sulfate deprivation did not seem to invest in new root axes. Crown roots presented anatomical differences in all parameters studied; e.g., more and larger xylem vessels in order to maximize water and nutrient transport in the xylem sap. In the root system of S-deficient plants, a reduced concentration of sulfur was observed, whilst organic sulfur predominated over sulfates. A reduction in total iron concentration was monitored, and differences in its subcellular localization were observed. As expected, S-deprivation negatively affected the total sulfur concentration in the aerial plant part, as well as greatly impacted iron allocation in the foliage. Phenotypic adaptation to sulfur deprivation in maize presented alterations mainly in the root anatomy; towards competent handling of the initial sulfur and the induced iron deficiencies.

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Febriana, Eni, Agus Budi Prasetyo, Wahyu Mayangsari, Januar Irawan, Muhammad Ikhwanul Hakim, Tiffany Ary Prakasa, Andinnie Juniarsih, Ariyo Suharyanto, Iwan Setiawan, and Rudi Subagja. "Effect of Sulfur Addition to Nickel Recovery of Laterite Ore." Jurnal Kimia Sains dan Aplikasi 23, no. 1 (November 17, 2019): 14–20. http://dx.doi.org/10.14710/jksa.23.1.14-20.

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This research studied the effect of the addition of sulfur on the reduction process of limonite nickel laterite ore with Ni content of 1.11wt% and Fe 48.7wt%. The stages of the research included the characterization of ore materials, preparation, mixing, pelleting, reduction, and magnetic separation. The reduction stage was carried out with several experimental variables, which were the time and temperature of the reduction, as well as the addition of reducing agents and sulfur additives. Products from the reduction process were separated magnetically, and the concentrate was then analyzed using XRD and AAS. The results showed that the addition of sulfur additives to a certain amount could cause the formation of FeS and Fe-silicate, which could increase the content and percentage of nickel recovery by suppressing the metallization of iron. The optimum conditions were obtained in the reduction process with a temperature of 1100°C for 60 minutes, with the addition of graphite reductant and sulfur additives each of 7% of the sample weight. Ni contents in the reduction product concentrate obtained were 1.98% with 96% gain, while Fe could be reduced to 29.2% with an extraction percentage of 76.1%.

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Yamashita, Takahiro, and Ryoko Yamamoto-Ikemoto. "Phosphate removal and sulfate reduction in a denitrification reactor packed with iron and wood as electron donors." Water Science and Technology 58, no. 7 (October 1, 2008): 1405–13. http://dx.doi.org/10.2166/wst.2008.728.

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Phosphorus removal and denitrification using iron and wood as electron donors were examined in a laboratory-scale biological filter reactor. Phosphorus removal and denitrification using iron and wood continued for 1,200 days of operation. Wood degradation by heterotrophic denitrification and iron oxidation by hydrogenotrophic denitrification occurred simultaneously. In the biofilm inside the wood, not only heterotrophic denitrification activity but also sulfate reduction and sulfur denitrification activities were recognized inside the wood, indicating that a sulfur oxidation-reduction cycle was established. Sulfate reduction and denitrification were accelerated with the addition of cellulose. Microbial communities of sulfate-reducing bacteria by PCR primer sets could be amplified in the biofilm in the reactors. The dissimilatory sulfite reductase gene and the 16S rRNA gene of six phylogenetic groups of SRB in the reactors were analyzed. Some SRB group-specific primers-amplification products were obtained inside the wood and around iron.

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Hong, Lan, Masahiro Hirasawa, Shinji Yamada, and Masamichi Sano. "Reduction of Iron Oxide in Sulfur Bearing Slag by Graphite." ISIJ International 36, no. 10 (1996): 1237–44. http://dx.doi.org/10.2355/isijinternational.36.1237.

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Myers, Charles R., and Kenneth H. Nealson. "Microbial reduction of manganese oxides: Interactions with iron and sulfur." Geochimica et Cosmochimica Acta 52, no. 11 (November 1988): 2727–32. http://dx.doi.org/10.1016/0016-7037(88)90041-5.

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32

You, Z., G. Li, Z. Peng, L. Qin, Y. Zhang, and T. Jiang. "Reductive roasting of iron-rich manganese oxide ore with elemental sulfur for selective manganese extraction." Journal of Mining and Metallurgy, Section B: Metallurgy 53, no. 2 (2017): 115–22. http://dx.doi.org/10.2298/jmmb150223008y.

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It is very important to selectively reduce manganese oxide over iron oxide for extraction of Mn from iron-rich manganese ore. In this study, reductive roasting of an iron-rich manganese oxide ore with elemental sulfur as reductant was investigated. The experimental results demonstrated that manganese dioxide can be selectively reduced with elemental sulfur and extracted via acid leaching, which was largely depended on the sulfur addition. Lower sulfur addition (S/Mn molar ratio<1.0) results in higher selectivity, which is independent of roasting temperature. More than 95% manganese and less than 10% iron were extracted through acid leaching under the roasting conditions of 400-600?C with S/Mn molar ratio of 0.6. The contents of manganese sulfide and sulfate in the roasted product increased with increasing sulfur addition, while they decreased distinctly at temperatures above 550?C. The thermodynamic analysis also proved that manganese dioxide is more easily reduced than iron oxide by sulfur at 300-900 K. The phase transformations during reductive roasting revealed that sulfides (MnS and FeS2) were favored at temperatures lower than 550?C whereas the oxides (MnFe2O4 and Fe3O4) were predominant at higher temperatures. The reduction of iron oxide mainly occurred at large sulfur additions (S/Mn>2.0) and the roasting temperature exerted a significant impact on the phase composition of roasted product.

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Ho, Que, Giridhar Anam, Jaein Kim, Somin Park, Tae-U. Lee, Jae-Young Jeon, Yun-Young Choi, Young-Ho Ahn, and Byung Lee. "Fate of Sulfate in Municipal Wastewater Treatment Plants and Its Effect on Sludge Recycling as a Fuel Source." Sustainability 15, no. 1 (December 25, 2022): 311. http://dx.doi.org/10.3390/su15010311.

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Wastewater sludge is used as an alternative fuel due to its high organic content and calorific value. However, influent characteristics and operational practices of wastewater treatment plants (WWTPs) can increase the sulfur content of sludge, devaluing it as a fuel. Thus, we investigated the biochemical mechanisms that elevate the sulfur content of sludge in a full-scale industrial WWTP receiving wastewater of the textile dyeing industry and a domestic WWTP by monitoring the sulfate, sulfur, and iron contents and the biochemical transformation of sulfate to sulfur in the wastewater and sludge treatment streams. A batch sulfate reduction rate test and microbial 16S rRNA and dsrB gene sequencing analyses were applied to assess the potential and activity of sulfate-reducing bacteria and their effect on sulfur deposition. This study indicated that the primary clarifier and anaerobic digester prominently reduced sulfate concentration through biochemical sulfate reduction and iron–sulfur complexation under anaerobic conditions, from 1247 mg/L in the influent to 6.2~59.8 mg/L in the industrial WWTP and from 46.7 mg/L to 0~0.8 mg/L in the domestic WWTPs. The anaerobic sludge, adapted in the high sulfate concentration of the industrial WWTP, exhibited a two times higher specific sulfate reduction rate (0.13 mg SO42−/gVSS/h) and sulfur content (3.14% DS) than the domestic WWTP sludge. Gene sequencing analysis of the population structure of common microbes and sulfate-reducing bacteria indicated the diversity of microorganisms involved in biochemical sulfate reduction in the sulfur cycle, supporting the data revealed by chemical analysis and batch tests.

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Yamamoto-Ikemoto, R., T. Komori, and S. Matsui. "Biological iron oxidation-reduction and the effects on sulfur oxidation-reduction, denitrification and poly-P accumulation in an anaerobic-oxic activated sludge." Water Science and Technology 46, no. 1-2 (July 1, 2002): 55–60. http://dx.doi.org/10.2166/wst.2002.0456.

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Iron oxidation and reduction were examined using the activated sludge from a municipal plant. Iron contents of the activated sludge were 1–2%. Iron oxidation rates were correlated with the initial iron concentrations. Iron reducing rates could be described by the Monod equation. The effects of iron reducing bacteria on sulfate reduction, denitrification and poly-P accumulation were examined. Iron reduction suppressed sulfate reduction by competing with hydrogen produced from protein. Denitrification was outcompeted with iron reduction and sulfate reduction. These phenomena could be explained thermodynamically. Poly-P accumulation was also suppressed by denitrification. The activity of iron reduction was relatively high.

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35

Escobar, Blanca, and Tomas Vargas. "Anaerobic Growth of Acidithiobacillus ferrooxidans on Pyrite." Advanced Materials Research 825 (October 2013): 96–99. http://dx.doi.org/10.4028/www.scientific.net/amr.825.96.

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In the bioleaching of mineral sulphides under the catalytic action ofAt. ferrooxidans,ferrous ion oxidation and sulfides/sulfur solubilization uses oxygen as the final electron acceptor. Also, under anaerobic conditions,At. ferrooxidanscan alternatively catalize the oxidation of sulfur or reduced inorganic sulfur compounds (RISC) using ferric iron as electron acceptor [1]. The formation of Fe (II) from pyrite and covellite in the ferric anaerobic bioleaching withA. ferrooxidans,has been studied and well documented [2,3]. The requirements of ferric iron as electron acceptor for the anaerobic growth ofAt. ferrooxidanson elemental sulfur has been demonstrated and a linear relationship was obtained between the concentration of ferrous iron accumulated in the cultures and the increase in cell density [4]. It has been suggested a possible role in the solubilization of metals from sulfide ores involving the participation of the enzyme sulfur (sulfide): Fe (III) oxidoreductase [5]. Bacterial growth ofAt. ferrooxidanshas also been reported in the oxidative anaerobic respiration using hydrogen as electron donor and ferric iron as electron acceptor [6]. Anaerobic reduction of ferric iron and ferrous iron production from pyrite byAt. ferrooxidanshas been demonstrated [2], however there are no reports about bacterial growth using this mineral. In this work, we studied the anaerobic bioleaching of pyrite with the aim to determine ifAt. ferrooxidansis capable to anaerobic growth on pyrite using ferric iron as electron acceptor.

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Hudson, Benjamin H., Andrew T. Hale, Ryan P. Irving, Shenglan Li, and John D. York. "Modulation of intestinal sulfur assimilation metabolism regulates iron homeostasis." Proceedings of the National Academy of Sciences 115, no. 12 (March 5, 2018): 3000–3005. http://dx.doi.org/10.1073/pnas.1715302115.

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Sulfur assimilation is an evolutionarily conserved pathway that plays an essential role in cellular and metabolic processes, including sulfation, amino acid biosynthesis, and organismal development. We report that loss of a key enzymatic component of the pathway, bisphosphate 3′-nucleotidase (Bpnt1), in mice, both whole animal and intestine-specific, leads to iron-deficiency anemia. Analysis of mutant enterocytes demonstrates that modulation of their substrate 3′-phosphoadenosine 5′-phosphate (PAP) influences levels of key iron homeostasis factors involved in dietary iron reduction, import and transport, that in part mimic those reported for the loss of hypoxic-induced transcription factor, HIF-2α. Our studies define a genetic basis for iron-deficiency anemia, a molecular approach for rescuing loss of nucleotidase function, and an unanticipated link between nucleotide hydrolysis in the sulfur assimilation pathway and iron homeostasis.

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37

Grzyb, Joanna, Ewelina Kalwarczyk, and Remigiusz Worch. "Photoreduction of natural redox proteins by CdTe quantum dots is size-tunable and conjugation-independent." RSC Advances 5, no. 76 (2015): 61973–82. http://dx.doi.org/10.1039/c5ra02900g.

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38

DENG, Gengfeng, Kun JIANG, Xia CAO, and Chunfa LIAO. "Reduction of SO2 to elemental sulfur over rare earth-iron catalysts." Journal of Rare Earths 27, no. 5 (October 2009): 744–48. http://dx.doi.org/10.1016/s1002-0721(08)60327-0.

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39

Gurung, Buddha, Linda Yu, and Chang-An Yu. "Stigmatellin Induces Reduction of Iron-Sulfur Protein in the Oxidized Cytochromebc1Complex." Journal of Biological Chemistry 283, no. 42 (August 13, 2008): 28087–94. http://dx.doi.org/10.1074/jbc.m804229200.

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40

Li, Liangtao, Ren Miao, Sophie Bertram, Xuan Jia, Diane M. Ward, and Jerry Kaplan. "A Role for Iron-Sulfur Clusters in the Regulation of Transcription Factor Yap5-dependent High Iron Transcriptional Responses in Yeast." Journal of Biological Chemistry 287, no. 42 (August 22, 2012): 35709–21. http://dx.doi.org/10.1074/jbc.m112.395533.

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Yeast respond to increased cytosolic iron by activating the transcription factor Yap5 increasing transcription of CCC1, which encodes a vacuolar iron importer. Using a genetic screen to identify genes involved in Yap5 iron sensing, we discovered that a mutation in SSQ1, which encodes a mitochondrial chaperone involved in iron-sulfur cluster synthesis, prevented expression of Yap5 target genes. We demonstrated that mutation or reduced expression of other genes involved in mitochondrial iron-sulfur cluster synthesis (YFH1, ISU1) prevented induction of the Yap5 response. We took advantage of the iron-dependent catalytic activity of Pseudaminobacter salicylatoxidans gentisate 1,2-dioxygenase expressed in yeast to measure changes in cytosolic iron. We determined that reductions in iron-sulfur cluster synthesis did not affect the activity of cytosolic gentisate 1,2-dioxygenase. We show that loss of activity of the cytosolic iron-sulfur cluster assembly complex proteins or deletion of cytosolic glutaredoxins did not reduce expression of Yap5 target genes. These results suggest that the high iron transcriptional response, as well as the low iron transcriptional response, senses iron-sulfur clusters.

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41

Jin, Yun, Qiquan Yu, and Shih-Ger Chang. "Reduction of sulfur dioxide by syngas to elemental sulfur over iron-based mixed oxide supported catalyst." Environmental Progress 16, no. 1 (1997): 1–8. http://dx.doi.org/10.1002/ep.3300160112.

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42

Kozuleva, Marina, Anastasia Petrova, Yuval Milrad, Alexey Semenov, Boris Ivanov, Kevin E. Redding, and Iftach Yacoby. "Phylloquinone is the principal Mehler reaction site within photosystem I in high light." Plant Physiology 186, no. 4 (May 7, 2021): 1848–58. http://dx.doi.org/10.1093/plphys/kiab221.

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Abstract Photosynthesis is a vital process, responsible for fixing carbon dioxide, and producing most of the organic matter on the planet. However, photosynthesis has some inherent limitations in utilizing solar energy, and a part of the energy absorbed is lost in the reduction of O2 to produce the superoxide radical (O2•−) via the Mehler reaction, which occurs principally within photosystem I (PSI). For decades, O2 reduction within PSI was assumed to take place solely in the distal iron–sulfur clusters rather than within the two asymmetrical cofactor branches. Here, we demonstrate that under high irradiance, O2 photoreduction by PSI primarily takes place at the phylloquinone of one of the branches (the A-branch). This conclusion derives from the light dependency of the O2 photoreduction rate constant in fully mature wild-type PSI from Chlamydomonas reinhardtii, complexes lacking iron–sulfur clusters, and a mutant PSI, in which phyllosemiquinone at the A-branch has a significantly longer lifetime. We suggest that the Mehler reaction at the phylloquinone site serves as a release valve under conditions where both the iron–sulfur clusters of PSI and the mobile ferredoxin pool are highly reduced.

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43

Gardner, Paul R. "Superoxide-Driven Aconitase FE-S Center Cycling." Bioscience Reports 17, no. 1 (February 1, 1997): 33–42. http://dx.doi.org/10.1023/a:1027383100936.

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O−2 produced by the autoxidation of respiratory chain electron carriers, and other cellular reductants, inactivates bacterial and mammalian iron-sulfur-containing (de)hydratases including the citric acid cycle enzyme aconitase. Release of the solvent-exposed iron atom and oxidation of the [4Fe-4S]2+ cluster accompanies loss of catalytic activity. Rapid reactivation is achieved by iron-sulfur cluster reduction and Fe2+ insertion. Inactivation-reactivation is a dynamic and cyclical process which modulates aconitase and (de)hydratase activities in Escherichia coli and mammalian cells. The balance of inactive and active aconitase provides a sensitive measure of the changes in steady-statO−2 levels occuring in living cells and mitochondria under stress conditions. Aconitases are also inactivated by other oxidants including O2, H2O2, NO., and ONOO− which are associated with inflammation, hyperoxia and other pathophysiological conditions. Loss of aconitase activity during oxidant stress may impair energy production, and the liberation of reactive iron may further enhance oxidative damage. Iron-sulfur center cycling may also serve adaptive functions by modulating gene expression or by signaling metabolic quiescence.

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44

Bigeev, Vachit A., Marina V. Potapova, and Irina V. Makarova. "Research of Ferronickel Manufacturing Process by Selective Reduction of Poor Iron-Chromium-Nickel Ores." Materials Science Forum 1052 (February 3, 2022): 244–49. http://dx.doi.org/10.4028/p-13f7ji.

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In metallurgy production nickel is an important alloying element used in the production of stainless, heat-resistant, acid-resistant grades of steel. For the development of ferronickel production in the Russian Federation, it is proposed to involve in processing complex poor iron-chromium-nickel ores of the Khalilovskoye deposit, which are not used at the present time. In the frame of this work the dependences of the elements reduction degrees of iron-chromium-nickel ore on the iron extraction degree were studied. These dependencies are necessary for the choice of the composition and development of ferronickel production technology. Burned ore raw materials were subjected to a selective carbothermal reduction in the laboratory electric arc furnace. In the obtained ferroalloy the nickel content decreased from 65 to 3%, phosphorus - from 0.68 to 0.38%, sulfur - from 0.19 to 0.10% with an increase in the reducing agent consumption. With the reduction of 1% iron, the recovery of nickel was only 50%, with 5% - 65–75%, with 20% - 95%. The content of iron oxides in the partially reduced melt with an increase in coke consumption decreased from 61 to 53%, and nickel oxide - from 0.192 to 0.010%. The analysis of the dependences allows us to make a conclusion that it is inappropriate to recover less than 5% of iron due to the low degree of nickel recovery (less than 70%). The rational degree of iron reduction from ore raw materials is 5-10%, which corresponds to the nickel content in the ferroalloy 10-20%, phosphorus - 0.3-0.5%, sulfur - 0.08-0.09%. Obviously, the resulting crude ferronickel needs refining, first of all dephosphorization.

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45

Suzuki, Isamu, Travis L. Takeuchi, Trin D. Yuthasastrakosol, and Jae Key Oh. "Ferrous Iron and Sulfur Oxidation and Ferric Iron Reduction Activities of Thiobacillus ferrooxidans Are Affected by Growth on Ferrous Iron, Sulfur, or a Sulfide Ore." Applied and Environmental Microbiology 56, no. 6 (1990): 1620–26. http://dx.doi.org/10.1128/aem.56.6.1620-1626.1990.

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46

Taha, Taher M., Fumiaki Takeuchi, and Tsuyoshi Sugio. "Reduction of Cytochrome c by Tetrathionate in the Presence of Tetrathionate Hydrolase Purified from Sulfur-Grown Acidithiobacillus Ferrooxidans ATCC 23270." Advanced Materials Research 71-73 (May 2009): 243–46. http://dx.doi.org/10.4028/www.scientific.net/amr.71-73.243.

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It is mysterious that, when A. ferrooxidans ATCC 23270 cells grow on elemental sulfur, they have high iron oxidase activity comparable to that of iron-grown cells as well as high activities of sulfide:ferric ion oxidoreductase (SFORase) and tetrathionate hydrolase. To clarify this interesting phenomenon, cytochrome c and tetrathionate hydrolase were purified from sulfur-grown A. ferrooxidans cells using ammonium sulfate precipitation, Phenyl column chromatography, and SuperdexTM 75 and Sephadex G-100 size exclusion column chromatographies. The purified cytochrome c was reduced by tetrathionate in the presence of purified tetrathionate hydrolase, but not in the absence of the enzyme. When the partially purified cytochrome c fraction containing aa3-type cytochrome oxidase was used, both cytochrome c and aa3-type cytochrome oxidase were reduced by tetrathionate in the presence of purified tetrathionate hydrolase. These results indicate that tetrathionate in the presence of tetrathionate hydrolase can reduce iron oxidase enzyme system containing cytochrome c and aa3-type cytochrome oxidase as tetrathionate hydrolase decomposes tetrathionate to produce thiosulfate, elemental sulfur, and sulfate; and the formed thiosulfate can chemically reduce cytochrome c and Fe3+.

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47

Joseph, Chris, John Patrick Shupp, Caitlyn R. Cobb, and Michael J. Rose. "Construction of Synthetic Models for Nitrogenase-Relevant NifB Biogenesis Intermediates and Iron-Carbide-Sulfide Clusters." Catalysts 10, no. 11 (November 13, 2020): 1317. http://dx.doi.org/10.3390/catal10111317.

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The family of nitrogenase enzymes catalyzes the reduction of atmospheric dinitrogen (N2) to ammonia under remarkably benign conditions of temperature, pressure, and pH. Therefore, the development of synthetic complexes or materials that can similarly perform this reaction is of critical interest. The primary obstacle for obtaining realistic synthetic models of the active site iron-sulfur-carbide cluster (e.g., FeMoco) is the incorporation of a truly inorganic carbide. This review summarizes the present state of knowledge regarding biological and chemical (synthetic) incorporation of carbide into iron-sulfur clusters. This includes the Nif cluster of proteins and associated biochemistry involved in the endogenous biogenesis of FeMoco. We focus on the chemical (synthetic) incorporation portion of our own efforts to incorporate and modify C1 units in iron/sulfur clusters. We also highlight recent contributions from other research groups in the area toward C1 and/or inorganic carbide insertion.

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Vigderovich, Hanni, Lewen Liang, Barak Herut, Fengping Wang, Eyal Wurgaft, Maxim Rubin-Blum, and Orit Sivan. "Evidence for microbial iron reduction in the methanic sediments of the oligotrophic southeastern Mediterranean continental shelf." Biogeosciences 16, no. 16 (August 23, 2019): 3165–81. http://dx.doi.org/10.5194/bg-16-3165-2019.

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Abstract. Dissimilatory iron reduction is probably one of the oldest types of metabolisms that still participates in important biogeochemical cycles, such as those of carbon and sulfur. It is one of the more energetically favorable anaerobic microbial respiration processes and is usually coupled to the oxidation of organic matter. Traditionally this process is thought to be limited to the shallow part of the sedimentary column in most aquatic systems. However, iron reduction has also been observed in the methanic zone of many marine and freshwater sediments, well below its expected zone and occasionally accompanied by decreases in methane, suggesting a link between the iron and the methane cycles. Nevertheless, the mechanistic nature of this link (competition, redox or other) has yet to be established and has not been studied in oligotrophic shallow marine sediments. In this study we present combined geochemical and molecular evidences for microbial iron reduction in the methanic zone of the oligotrophic southeastern (SE) Mediterranean continental shelf. Geochemical porewater profiles indicate iron reduction in two zones, the uppermost part of the sediment, and the deeper zone, in the layer of high methane concentration. Results from a slurry incubation experiment indicate that the deep methanic iron reduction is microbially mediated. The sedimentary profiles of microbial abundance and quantitative PCR (qPCR) of the mcrA gene, together with Spearman correlation between the microbial data and Fe(II) concentrations in the porewater, suggest types of potential microorganisms that may be involved in the iron reduction via several potential pathways: H2 or organic matter oxidation, an active sulfur cycle, or iron-driven anaerobic oxidation of methane. We suggest that significant upward migration of methane in the sedimentary column and its oxidation by sulfate may fuel the microbial activity in the sulfate methane transition zone (SMTZ). The biomass created by this microbial activity can be used by the iron reducers below, in the methanic zone of the sediments of the SE Mediterranean.

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Amdur, A. M., D. V. Blagin, V. V. Pavlov, and L. Munkhtuul. "Removal of sulfur in the reduction of iron-ore concentrates by coal." Coke and Chemistry 56, no. 3 (March 2013): 81–84. http://dx.doi.org/10.3103/s1068364x13030034.

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Yu, Cheol Su, Hyukjae Choi, and Sunghyun Kim. "Electrocatalytic Reduction of Sulfur Dioxide by Iron Phthalocyanine Monolayer in Acidic Conditions." Chemistry Letters 31, no. 7 (July 2002): 648–49. http://dx.doi.org/10.1246/cl.2002.648.

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Journal articles on the topic 'Sulfur and iron reduction'

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