Microbial Leaching of Iron from Hematite: Direct or Indirect Elution

Aneksampant, Apichaya; Nakashima, Kazunori; Kawasaki, Satoru

doi:10.2320/matertrans.m-m2019860

Cited by 4 publications

(2 citation statements)

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“…It is noteworthy that all homoacetogens tested in this study, except for A. woodii , reduced crystalline Fe(III) oxides (goethite and hematite) ( Figure 6 ), because only limited members of IRBs, in particular, bacteria belonging to Geobacter and Shewanella , can directly reduce crystalline Fe(III) ( Roden and Urrutia, 2002 ; Behrends and van Cappellen, 2007 ; Yan et al, 2008 ; Bose et al, 2009 ; Aneksampant et al, 2020 ; Hu et al, 2020 ). Results in this study broaden our knowledge on the role of mesophilic homoacetogens in the reduction and dissolution of crystalline Fe(III) oxides in nature.…”

Section: Discussionmentioning

confidence: 87%

Reductive Transformation of Fe(III) (oxyhydr)Oxides by Mesophilic Homoacetogens in the Genus Sporomusa

Igarashi

Kato

2021

Front. Microbiol.

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Microbial reduction of iron contributes to the dissolution and transformation of iron-containing minerals in nature. Diverse groups of homoacetogenic bacteria (homoacetogens) have been reported to reduce insoluble Fe(III) oxides, such as hydrous ferric oxide (HFO), an Fe(III) mineral commonly found in soils and sediments. Several members of genus Sporomusa reportedly oxidize Fe(0), indicating the presence of an extracellular electron-uptake mechanism. However, the ability of the genus to reduce insoluble Fe(III) oxides is limited, and the underlying reduction mechanism remains to be elucidated. In this study, the HFO reduction ability of three Sporomusa spp. (Sporomusa sp. strain GT1, Sporomusa sphaeroides, and Sporomusa ovata) and a homoacetogen of a different genus (Acetobacterium woodii) were assayed under organotrophic (ethanol) and lithotrophic (H2 + CO2) conditions without a chelator or reducing reagent. All tested homoacetogens showed acetogenic growth and concomitant reduction of HFO under both organotrophic and lithotrophic conditions. Analysis of the growth stoichiometry showed that Fe(III) reduction does not support direct energy conservation, thereby indicating that Fe(III) reduction is a side reaction of acetogenesis to dissipate the excess reducing power. HFO was reduced to a soluble Fe(II) form by microbial activity. In addition, we observed that strain GT1, S. sphaeroides, and S. ovata reduced crystalline Fe(III) oxides, and HFO was reductively transformed into magnetite (Fe3O4) under phosphate-limiting conditions. Separation of HFO by a dialysis membrane still permitted Fe(II) production, although the reduction rate was decreased, suggesting that Fe(III) reduction is at least partially mediated by soluble redox compound(s) secreted from the cells. Finally, culture experiments and comparative genomic analysis suggested that electron transfer by flavins and multiheme c-type cytochrome were not directly correlated with Fe(III) reduction activity. This study reveals the capability of Sporomusa spp. in the reductive transformation of iron mineral and indicates the potential involvement of these organisms in iron and other mineral cycles in nature.

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Section: Discussionmentioning

confidence: 87%

Reductive Transformation of Fe(III) (oxyhydr)Oxides by Mesophilic Homoacetogens in the Genus Sporomusa

Igarashi

Kato

2021

Front. Microbiol.

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“…21) On the other hand, ferrous ion [Fe (II)] released from slag is soluble yet easy to be oxidized to insoluble ferric ion [Fe (III)], 22,23) which is not absorbable to seaweeds. Although bacteria can help to reduce ferric ion back to ferrous ion, 24) a high concentration of bacteria in seawater is required. Therefore, pretreatment of BOF steelmaking slag and lifetime extension of soluble Fe ions in seawater are the difficulties to be addressed.…”

Section: Introductionmentioning

confidence: 99%

Recycling of Steelmaking Slag in Seawater as an Iron Supplier: Effects of Slag Composition, Carbonation and Usage of Gluconic Acid

et al. 2021

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Disappearing of benthic seaweeds in coastal areas has gradually become a serious environmental problem worldwide. One possible reason is iron deficiency in seawater. As a major byproduct generated in steelmaking industry, steelmaking slag is rich in Fe and has the potential to restore seaweeds by supplying soluble Fe in seawater. The authors aim to develop a sustainable approach for ecosystem restoration in coastal areas by utilizing steelmaking slag. This work investigates the releasing behavior of elements from synthesized steelmaking slags in seawater and clarifies the effects of slag composition, carbonation and usage of gluconic acid. Slag with larger CaO/SiO 2 ratio (= 3.0) has difficulty in releasing Fe into seawater directly, due to drastic increase of pH. Combination of slag carbonation and gluconic acid usage is necessary and effective in boosting release of Fe. Slag with smaller CaO/SiO 2 ratio (= 1.0) would not cause drastic increase of pH in seawater and thus releasing of Fe is easier. These results have proved the potential value and feasibility of using steelmaking slag as an underwater iron fertilizer.

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