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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.


Geobacter sulfurreducens growth curves: (a) 100 ml bottles; (b) 5 l bioreactor; (c) 50 l bioreactor. Biomass measured as dry weight protein (g l−1), represented by (circle), pH (square) and redox (mV) (triangle); pH was not controlled during the experiments. (Online version in colour.)
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RSIF20150240F3: Geobacter sulfurreducens growth curves: (a) 100 ml bottles; (b) 5 l bioreactor; (c) 50 l bioreactor. Biomass measured as dry weight protein (g l−1), represented by (circle), pH (square) and redox (mV) (triangle); pH was not controlled during the experiments. (Online version in colour.)

Mentions: Biomass density (OD600 converted to g l−1 dry weight), redox (mV) and pH of the G. sulfurreducens culture were monitored over 48 h in 5 l and 50 l bioreactors with results compared to the growth profile obtained in 100 ml bottles (figure 3). A 10% inoculum from a late exponential phase starter culture was used throughout. There was a significant increase in the lag phase of the cultures with increasing vessel volume, with the 100 ml culture exhibiting the shortest lag phase. The reasons for this were not clear; however, it might be due to the presence of an impellor which was not present for the 100 ml samples, but was for 5 l and 50 l bioreactors. The impellor was used to prevent the formation of a biofilm on the walls of the vessels; however, it is not known what effects the mixing of the culture medium could have on microbial growth. The doubling time was approximately 5.7 h and 3.8 h for the 100 ml and 50 l cultures, respectively. Final biomass yields were similar for all volumes: 0.198 g l−1, 0.187 g l−1 and 0.215 g l−1 (dry weight) for 100 ml, 5 l and 50 l production runs, respectively. The pH in 5 l and 50 l cultures remained circumneutral, with a minor decrease seen in the 5 l bioreactor and a minor increase seen in the 50 l bioreactor. Redox values in both vessels decreased as cultures grew, with a maximal drop from +180 to −362 mV and from +37 to −440 mV for 5 l and 50 l cultures, respectively.Figure 3.


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)

Geobacter sulfurreducens growth curves: (a) 100 ml bottles; (b) 5 l bioreactor; (c) 50 l bioreactor. Biomass measured as dry weight protein (g l−1), represented by (circle), pH (square) and redox (mV) (triangle); pH was not controlled during the experiments. (Online version in colour.)
© Copyright Policy - open-access
Related In: Results  -  Collection

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

RSIF20150240F3: Geobacter sulfurreducens growth curves: (a) 100 ml bottles; (b) 5 l bioreactor; (c) 50 l bioreactor. Biomass measured as dry weight protein (g l−1), represented by (circle), pH (square) and redox (mV) (triangle); pH was not controlled during the experiments. (Online version in colour.)
Mentions: Biomass density (OD600 converted to g l−1 dry weight), redox (mV) and pH of the G. sulfurreducens culture were monitored over 48 h in 5 l and 50 l bioreactors with results compared to the growth profile obtained in 100 ml bottles (figure 3). A 10% inoculum from a late exponential phase starter culture was used throughout. There was a significant increase in the lag phase of the cultures with increasing vessel volume, with the 100 ml culture exhibiting the shortest lag phase. The reasons for this were not clear; however, it might be due to the presence of an impellor which was not present for the 100 ml samples, but was for 5 l and 50 l bioreactors. The impellor was used to prevent the formation of a biofilm on the walls of the vessels; however, it is not known what effects the mixing of the culture medium could have on microbial growth. The doubling time was approximately 5.7 h and 3.8 h for the 100 ml and 50 l cultures, respectively. Final biomass yields were similar for all volumes: 0.198 g l−1, 0.187 g l−1 and 0.215 g l−1 (dry weight) for 100 ml, 5 l and 50 l production runs, respectively. The pH in 5 l and 50 l cultures remained circumneutral, with a minor decrease seen in the 5 l bioreactor and a minor increase seen in the 50 l bioreactor. Redox values in both vessels decreased as cultures grew, with a maximal drop from +180 to −362 mV and from +37 to −440 mV for 5 l and 50 l cultures, respectively.Figure 3.

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.