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Scale-up of the production of highly reactive biogenic magnetite nanoparticles using Geobacter sulfurreducens.

Byrne JM, Muhamadali H, Coker VS, Cooper J, Lloyd JR - J R Soc Interface (2015)

Bottom Line: This procedure was capable of producing up to 120 g of biomagnetite.The particle size distribution was maintained between 10 and 15 nm during scale-up of this second step from 10 ml to 10 l, with conserved magnetic properties and surface reactivity; the latter demonstrated by the reduction of Cr(VI).The process presented provides an environmentally benign route to magnetite production and serves as an alternative to harsher synthetic techniques, with the clear potential to be used to produce kilogram to tonne quantities.

View Article: PubMed Central - PubMed

Affiliation: School of Earth, Atmospheric and Environmental Sciences, and Williamson Research Centre for Molecular Environmental Science, University of Manchester, Manchester M13 9PL, UK Geomicrobiology, Center for Applied Geoscience, University of Tuebingen, Sigwartstrasse 10, 72076 Tuebingen, Germany.

ABSTRACT
Although there are numerous examples of large-scale commercial microbial synthesis routes for organic bioproducts, few studies have addressed the obvious potential for microbial systems to produce inorganic functional biomaterials at scale. Here we address this by focusing on the production of nanoscale biomagnetite particles by the Fe(III)-reducing bacterium Geobacter sulfurreducens, which was scaled up successfully from laboratory- to pilot plant-scale production, while maintaining the surface reactivity and magnetic properties which make this material well suited to commercial exploitation. At the largest scale tested, the bacterium was grown in a 50 l bioreactor, harvested and then inoculated into a buffer solution containing Fe(III)-oxyhydroxide and an electron donor and mediator, which promoted the formation of magnetite in under 24 h. This procedure was capable of producing up to 120 g of biomagnetite. The particle size distribution was maintained between 10 and 15 nm during scale-up of this second step from 10 ml to 10 l, with conserved magnetic properties and surface reactivity; the latter demonstrated by the reduction of Cr(VI). The process presented provides an environmentally benign route to magnetite production and serves as an alternative to harsher synthetic techniques, with the clear potential to be used to produce kilogram to tonne quantities.

No MeSH data available.


(a) X-ray absorption spectra (XAS) of samples obtained through Fe(III) reduction in volumes of 10 ml, 100 ml, 1 l and 10 l. ‘Bio mag’ corresponds to sample of biogenic magnetite [35] with close to stoichiometric cation distribution. (b) X-ray magnetic circular dichroism (XMCD) with peaks corresponding to Fe2+[B], Fe3+(A) and Fe3+[B] as highlighted by fits in blue, red and green, respectively. (Online version in colour.)
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RSIF20150240F5: (a) X-ray absorption spectra (XAS) of samples obtained through Fe(III) reduction in volumes of 10 ml, 100 ml, 1 l and 10 l. ‘Bio mag’ corresponds to sample of biogenic magnetite [35] with close to stoichiometric cation distribution. (b) X-ray magnetic circular dichroism (XMCD) with peaks corresponding to Fe2+[B], Fe3+(A) and Fe3+[B] as highlighted by fits in blue, red and green, respectively. (Online version in colour.)

Mentions: Synchrotron radiation techniques, XAS and XMCD were used to determine the distribution of iron in the biomagnetite (figure 5). Magnetite has a cubic spinel structure with Fe2+ and Fe3+ cations arranged in tetrahedral (A) and octahedral [B] coordination according to (Fe3+)A[Fe2+Fe3+]BO42−. Anti-ferromagnetic coupling between the two lattice sites effectively cancels out the magnetic moments of Fe3+ cations, resulting in net magnetization owing to Fe2+. The XAS of the Fe L2,3 edges (formed from the average of±0.6 T spectra) (figure 5a) showed little differences between each sample despite the presence of siderite in 1 l and 10 l samples (haematite was present in all samples), indicating that it is only a minor component. Spectra were compared with a sample of biogenic magnetite from small-scale culture, reported previously [35], designated ‘Bio mag’ and known to have a close to stoichiometric cation distribution (table 1) with a slight excess of octahedral Fe2+[B], (Fe2+/Fe3+ 0.52). This is characterized by a smooth shoulder on the low energy side of the peak intensity (dashed line). The shoulder is more pronounced in the 50 l fermenter derived samples, which is indicative of a less reduced sample (i.e. less Fe2+[B] in relation to other Fe cations). However, it is more likely to be due to the presence of the Fe(III) oxide haematite which is not present in the reference ‘Bio mag’ sample [35].Table 1.


Scale-up of the production of highly reactive biogenic magnetite nanoparticles using Geobacter sulfurreducens.

Byrne JM, Muhamadali H, Coker VS, Cooper J, Lloyd JR - J R Soc Interface (2015)

(a) X-ray absorption spectra (XAS) of samples obtained through Fe(III) reduction in volumes of 10 ml, 100 ml, 1 l and 10 l. ‘Bio mag’ corresponds to sample of biogenic magnetite [35] with close to stoichiometric cation distribution. (b) X-ray magnetic circular dichroism (XMCD) with peaks corresponding to Fe2+[B], Fe3+(A) and Fe3+[B] as highlighted by fits in blue, red and green, respectively. (Online version in colour.)
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4590511&req=5

RSIF20150240F5: (a) X-ray absorption spectra (XAS) of samples obtained through Fe(III) reduction in volumes of 10 ml, 100 ml, 1 l and 10 l. ‘Bio mag’ corresponds to sample of biogenic magnetite [35] with close to stoichiometric cation distribution. (b) X-ray magnetic circular dichroism (XMCD) with peaks corresponding to Fe2+[B], Fe3+(A) and Fe3+[B] as highlighted by fits in blue, red and green, respectively. (Online version in colour.)
Mentions: Synchrotron radiation techniques, XAS and XMCD were used to determine the distribution of iron in the biomagnetite (figure 5). Magnetite has a cubic spinel structure with Fe2+ and Fe3+ cations arranged in tetrahedral (A) and octahedral [B] coordination according to (Fe3+)A[Fe2+Fe3+]BO42−. Anti-ferromagnetic coupling between the two lattice sites effectively cancels out the magnetic moments of Fe3+ cations, resulting in net magnetization owing to Fe2+. The XAS of the Fe L2,3 edges (formed from the average of±0.6 T spectra) (figure 5a) showed little differences between each sample despite the presence of siderite in 1 l and 10 l samples (haematite was present in all samples), indicating that it is only a minor component. Spectra were compared with a sample of biogenic magnetite from small-scale culture, reported previously [35], designated ‘Bio mag’ and known to have a close to stoichiometric cation distribution (table 1) with a slight excess of octahedral Fe2+[B], (Fe2+/Fe3+ 0.52). This is characterized by a smooth shoulder on the low energy side of the peak intensity (dashed line). The shoulder is more pronounced in the 50 l fermenter derived samples, which is indicative of a less reduced sample (i.e. less Fe2+[B] in relation to other Fe cations). However, it is more likely to be due to the presence of the Fe(III) oxide haematite which is not present in the reference ‘Bio mag’ sample [35].Table 1.

Bottom Line: This procedure was capable of producing up to 120 g of biomagnetite.The particle size distribution was maintained between 10 and 15 nm during scale-up of this second step from 10 ml to 10 l, with conserved magnetic properties and surface reactivity; the latter demonstrated by the reduction of Cr(VI).The process presented provides an environmentally benign route to magnetite production and serves as an alternative to harsher synthetic techniques, with the clear potential to be used to produce kilogram to tonne quantities.

View Article: PubMed Central - PubMed

Affiliation: School of Earth, Atmospheric and Environmental Sciences, and Williamson Research Centre for Molecular Environmental Science, University of Manchester, Manchester M13 9PL, UK Geomicrobiology, Center for Applied Geoscience, University of Tuebingen, Sigwartstrasse 10, 72076 Tuebingen, Germany.

ABSTRACT
Although there are numerous examples of large-scale commercial microbial synthesis routes for organic bioproducts, few studies have addressed the obvious potential for microbial systems to produce inorganic functional biomaterials at scale. Here we address this by focusing on the production of nanoscale biomagnetite particles by the Fe(III)-reducing bacterium Geobacter sulfurreducens, which was scaled up successfully from laboratory- to pilot plant-scale production, while maintaining the surface reactivity and magnetic properties which make this material well suited to commercial exploitation. At the largest scale tested, the bacterium was grown in a 50 l bioreactor, harvested and then inoculated into a buffer solution containing Fe(III)-oxyhydroxide and an electron donor and mediator, which promoted the formation of magnetite in under 24 h. This procedure was capable of producing up to 120 g of biomagnetite. The particle size distribution was maintained between 10 and 15 nm during scale-up of this second step from 10 ml to 10 l, with conserved magnetic properties and surface reactivity; the latter demonstrated by the reduction of Cr(VI). The process presented provides an environmentally benign route to magnetite production and serves as an alternative to harsher synthetic techniques, with the clear potential to be used to produce kilogram to tonne quantities.

No MeSH data available.