Biological Cr(VI) Reduction: Microbial Diversity, Kinetics and Biotechnological Solutions to Pollution

Chirwa, Evans M.N.; Molokwane, Pulane E.

doi:10.5772/24311

Cited by 13 publications

(10 citation statements)

References 54 publications

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“…Various mechanisms of Cr(VI) resistance or detoxification have been described, such as the efflux of chromate ions from the cell cytoplasm, reduction of extracellular Cr(VI) to Cr(III) [ 45 ], activation of enzymes involved in the ROS detoxifying processes (e.g., catalase, superoxide dismutase), repair of DNA lesions by SOS response enzymes (RecA, RecG, RuvAB), and regulation of iron uptake to prevent the production of hydroxyl radicals through the fenton reaction [ 46 ].…”

Section: Resultsmentioning

confidence: 99%

“…Chromate resistance determinants (CRDs) have been identified in Archaea, Bacteria and Eukarya, and consist of genes belonging to the chromate ion transport (CHR) superfamily [ 47 ]. Generally, CRDs include the ChrA gene, which encodes a putative chromate efflux protein driven by the membrane potential [ 46 ]. In bacteria, the ChrA genes can be located on plasmid or chromosomal DNA or both [ 48 ], and they are generally organized in operons with other ChrR genes.…”

Section: Resultsmentioning

confidence: 99%

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Reduction of Hexavalent Chromium and Detection of Chromate Reductase (ChrR) in Stenotrophomonas maltophilia

et al. 2018

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An Gram negative strain of S. maltophilia, indigenous to environments contaminated by Cr(VI) and identified by biochemical methods and 16S rRNA gene analysis, reduced chromate by 100%, 98–99% and 92% at concentrations in the 10–70, 80–300, and 500 mg/L range, respectively at pH 7 and temperature 37 °C. Increasing concentrations of Cr(VI) in the medium lowered the growth rate but could not be directly correlated with the amount of Cr(VI) reduced. The strain also exhibited multiple resistance to antibiotics and tolerance and resistance to various heavy metals (Ni, Zn and Cu), with the exception of Hg. Hexavalent chromium reduction was mainly associated with the soluble fraction of the cell evaluated with crude cell-free extracts. A protein of molecular weight around 25 kDa was detected on SDS-PAGE gel depending on the concentration of hexavalent chromium in the medium (0, 100 and 500 mg/L). In silico analysis in this contribution, revealed the presence of the chromate reductase gene ChrR in S. maltophilia, evidenced through a fragment of around 468 bp obtained experimentally. High Cr(VI) concentration resistance and high Cr(VI) reducing ability of the strain make it a suitable candidate for bioremediation.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Reduction of Hexavalent Chromium and Detection of Chromate Reductase (ChrR) in Stenotrophomonas maltophilia

et al. 2018

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“…46 Alternatively, the Cr(VI) may have been reduced by extracellular soluble reductase excreted by the fungi, similar to that of certain Gram-negative bacteria. 47 Another possibility is that Cr(VI) was first reduced in the fungi or on the fungal surface by chromate reductase or intracellular compounds (e.g., cysteine, glutathione, and sulfite), and then some Cr(III) in the fungal…”

Section: Environmental Science and Technologymentioning

confidence: 99%

Transformation and Immobilization of Chromium by Arbuscular Mycorrhizal Fungi as Revealed by SEM–EDS, TEM–EDS, and XAFS

Xin²,

Sun

et al. 2015

Environ. Sci. Technol.

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Arbuscular mycorrhizal fungi (AMF), ubiquitous soil fungi that form symbiotic relationships with the majority of terrestrial plants, are known to play an important role in plant tolerance to chromium (Cr) contamination. However, the underlying mechanisms, especially the direct influences of AMF on the translocation and transformation of Cr in the soil−plant continuum, are still unresolved. In a two-compartment root-organ cultivation system, the extraradical mycelium (ERM) of mycorrhizal roots was treated with 0.05 mmol L −1 Cr(VI) for 12 days to investigate the uptake, translocation, and transformation of Cr(VI) by AMF using inductively coupled plasma mass spectrometry (ICP-MS), scanning electron microscopy equipped with energy-dispersive spectroscopy (SEM−EDS), transmission electron microscopy equipped with energy-dispersive spectroscopy (TEM−EDS), and X-ray-absorption fine structure (XAFS) technologies. The results indicated that AMF can immobilize quantities of Cr via reduction of Cr(VI) to Cr(III), forming Cr(III)−phosphate analogues, likely on the fungal surface. Besides this, we also confirmed that the extraradical mycelium (ERM) can actively take up Cr [either in the form of Cr(VI) or Cr(III)] and transport Cr [potentially in the form of Cr(III)-histidine analogues] to mycorrhizal roots but immobilize most of the Cr(III) in the fungal structures. Based on an X-ray absorption nearedge spectroscopy analysis of Cr(VI)-treated roots, we proposed that the intraradical fungal structures can also immobilize Cr within mycorrhizal roots. Our findings confirmed the immobilization of Cr by AMF, which plays an essential role in the Cr(VI) tolerance of AM symbioses.

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“…The reduction can be done by organic compounds [3], bacteria [4], and enzymes or nonenzymatic agents derived from plants [5]. Photoreduction process is an alternative route for the reduction of Cr(VI).…”

Section: Introductionmentioning

confidence: 99%

Comparison of ZrO₂, TiO₂, and α-Fe₂O₃ nanotube arrays on Cr(VI) photoreduction fabricated by anodization of Zr, Ti, and Fe foils

Bashirom

Tan

Kawamura

et al. 2020

Mater. Res. Express

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This paper presents the fabrication of self-organized ZrO 2 , TiO 2 , and α-Fe 2 O 3 nanotube arrays by anodization of Zr, Ti, and Fe foils, respectively in fluoride-containing EG electrolyte at 40 V for 20 min. The as-anodized nanotubes were annealed in a tube furnace at 400°C for 3 h to induce the crystallization of the oxide film. Morphology, crystal structure, surface properties, and optical properties of the anodic ZrO 2 nanotubes (ZNTs), TiO 2 nanotubes (TNTs), and α-Fe 2 O 3 nanotubes (FNTs) were characterized by Field-Emission Scanning Electron Microscopy (FESEM), Transmission Electron Microscopy (TEM), x-ray Diffraction (XRD), Fourier-Transform Infrared (FTIR) spectroscopy, Photoluminescence (PL) spectroscopy, and UV-visible Near-Infrared Diffuse Reflectance Spectra (UV-vis NIR DRS) spectroscopy, respectively. Based on the FESEM and TEM micrographs, ZNTs possessed the longest nanotubes (i.e. 9.6 μm) compared with TNTs and FNTs under the same anodization condition. The aspect ratio of the nanotubes can be arranged in the order of ZNTs>FNTs>TNTs. The surface of the annealed ZNTs, FNTs, and TNTs was enriched with -OH groups to facilitate the Cr(VI) adsorption. According to the UV-vis NIR DRS spectra, strong visible light absorption was observed on the FNTs due to their low band gap. Whereas, the TNTs predominantly absorbs the UV light at λ max =360 nm. Rapid Cr(VI) removal was observed on FNTs, i.e. 100% after 2 h activated by sunlight with negligible Cr(VI) removal for ZNTs and TNTs. When exposed to UVC (λ=254 nm), only 39% versus 37% Cr(VI) removal efficiencies were obtained on TNTs and ZNTs after 3 h suggesting sluggish electron transfer due to rapid charge carriers recombination as evident in the PL spectra.

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Biological Cr(VI) Reduction: Microbial Diversity, Kinetics and Biotechnological Solutions to Pollution

Cited by 13 publications

References 54 publications

Reduction of Hexavalent Chromium and Detection of Chromate Reductase (ChrR) in Stenotrophomonas maltophilia

Reduction of Hexavalent Chromium and Detection of Chromate Reductase (ChrR) in Stenotrophomonas maltophilia

Transformation and Immobilization of Chromium by Arbuscular Mycorrhizal Fungi as Revealed by SEM–EDS, TEM–EDS, and XAFS

Comparison of ZrO₂, TiO₂, and α-Fe₂O₃ nanotube arrays on Cr(VI) photoreduction fabricated by anodization of Zr, Ti, and Fe foils

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Biological Cr(VI) Reduction: Microbial Diversity, Kinetics and Biotechnological Solutions to Pollution

Cited by 13 publications

References 54 publications

Reduction of Hexavalent Chromium and Detection of Chromate Reductase (ChrR) in Stenotrophomonas maltophilia

Reduction of Hexavalent Chromium and Detection of Chromate Reductase (ChrR) in Stenotrophomonas maltophilia

Transformation and Immobilization of Chromium by Arbuscular Mycorrhizal Fungi as Revealed by SEM–EDS, TEM–EDS, and XAFS

Comparison of ZrO2, TiO2, and α-Fe2O3 nanotube arrays on Cr(VI) photoreduction fabricated by anodization of Zr, Ti, and Fe foils

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Comparison of ZrO₂, TiO₂, and α-Fe₂O₃ nanotube arrays on Cr(VI) photoreduction fabricated by anodization of Zr, Ti, and Fe foils