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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.


Growth of Geobacter sulfurreducens in a 5 l bioreactor: (a) 100 ml, 0 r.p.m. stirrer speed, no pH control during experiment; (b) 5 l, 100 r.p.m. stirrer speed, pH controlled with 2 M HCl and 2 M NaOH; (c) 5 l, 100 r.p.m. stirrer speed, pH controlled with 1 M MOPS (pH 4.1) and 2 M NaOH; (d) 5 l, 100 r.p.m. stirrer speed, no pH control during experiment; (e) 5 l, 0 r.p.m. stirrer speed, no pH control; (f) 5 l, 50 r.p.m. stirrer speed, no pH control. (Online version in colour.)
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RSIF20150240F2: Growth of Geobacter sulfurreducens in a 5 l bioreactor: (a) 100 ml, 0 r.p.m. stirrer speed, no pH control during experiment; (b) 5 l, 100 r.p.m. stirrer speed, pH controlled with 2 M HCl and 2 M NaOH; (c) 5 l, 100 r.p.m. stirrer speed, pH controlled with 1 M MOPS (pH 4.1) and 2 M NaOH; (d) 5 l, 100 r.p.m. stirrer speed, no pH control during experiment; (e) 5 l, 0 r.p.m. stirrer speed, no pH control; (f) 5 l, 50 r.p.m. stirrer speed, no pH control. (Online version in colour.)

Mentions: An intermediate scale bioreactor (7 l) was used for biomass production containing the defined medium with 50 mM acetate and 80 mM fumarate. The initial growth medium experiments were 100 ml bottles that were de-gassed (and pH neutralized) with an 80 : 20 N2 : CO2 gas mix before being sealed and autoclaved. Sterilization using this approach was not possible in the bioreactor, as the pressure vessel was unable to withstand high pressures without using venting ports. These venting ports permitted the backflow of oxygen into the system post autoclaving. Additionally, only N2 gas was available in the pilot plant for the 50 l fermenter, hence an alternative method other than gassing with 20% CO2 was required to lower the pH of the bicarbonate-containing growth medium to pH 7. Figure 2 shows the growth of G. sulfurreducens measured in the 7 l bioreactor containing 5 l medium and with a range of pH control methods (figure 2a).Figure 2.


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)

Growth of Geobacter sulfurreducens in a 5 l bioreactor: (a) 100 ml, 0 r.p.m. stirrer speed, no pH control during experiment; (b) 5 l, 100 r.p.m. stirrer speed, pH controlled with 2 M HCl and 2 M NaOH; (c) 5 l, 100 r.p.m. stirrer speed, pH controlled with 1 M MOPS (pH 4.1) and 2 M NaOH; (d) 5 l, 100 r.p.m. stirrer speed, no pH control during experiment; (e) 5 l, 0 r.p.m. stirrer speed, no pH control; (f) 5 l, 50 r.p.m. stirrer speed, no pH control. (Online version in colour.)
© Copyright Policy - open-access
Related In: Results  -  Collection

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

RSIF20150240F2: Growth of Geobacter sulfurreducens in a 5 l bioreactor: (a) 100 ml, 0 r.p.m. stirrer speed, no pH control during experiment; (b) 5 l, 100 r.p.m. stirrer speed, pH controlled with 2 M HCl and 2 M NaOH; (c) 5 l, 100 r.p.m. stirrer speed, pH controlled with 1 M MOPS (pH 4.1) and 2 M NaOH; (d) 5 l, 100 r.p.m. stirrer speed, no pH control during experiment; (e) 5 l, 0 r.p.m. stirrer speed, no pH control; (f) 5 l, 50 r.p.m. stirrer speed, no pH control. (Online version in colour.)
Mentions: An intermediate scale bioreactor (7 l) was used for biomass production containing the defined medium with 50 mM acetate and 80 mM fumarate. The initial growth medium experiments were 100 ml bottles that were de-gassed (and pH neutralized) with an 80 : 20 N2 : CO2 gas mix before being sealed and autoclaved. Sterilization using this approach was not possible in the bioreactor, as the pressure vessel was unable to withstand high pressures without using venting ports. These venting ports permitted the backflow of oxygen into the system post autoclaving. Additionally, only N2 gas was available in the pilot plant for the 50 l fermenter, hence an alternative method other than gassing with 20% CO2 was required to lower the pH of the bicarbonate-containing growth medium to pH 7. Figure 2 shows the growth of G. sulfurreducens measured in the 7 l bioreactor containing 5 l medium and with a range of pH control methods (figure 2a).Figure 2.

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.