Enhanced Yields of Iron-Oxidizing Bacteria by In Situ Electrochemical Reduction of Soluble Iron in the Growth Medium

Blake, Robert C.; Howard, Gary T.; McGinness, Stephen

doi:10.1128/aem.60.8.2704-2710.1994

Cited by 51 publications

(26 citation statements)

References 25 publications

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“…These results demonstrate that electrodes can serve as an electron donor for microbial reduction of electron acceptors in Geobacter species. Although electrodes have previously been used to regenerate Fe(II) from Fe(III) as an electron donor in the metabolism of Acidithiobacillus (formerly Thiobacillus) (Blake et al, 1994), to our knowledge, the results presented here demonstrate for the first time that electrodes have been found to serve as direct electron donors. As discussed below, this finding has potential applications for manipulating microbial respiration in anaerobic sedimentary environments.…”

Section: Discussionmentioning

confidence: 70%

Graphite electrodes as electron donors for anaerobic respiration

Gregory

Bond

Lovley³

2004

Environmental Microbiology

685

460

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It has been demonstrated previously that Geobacter species can transfer electrons directly to electrodes. In order to determine whether electrodes could serve as electron donors for microbial respiration, enrichment cultures were established from a sediment inoculum with a potentiostat-poised graphite electrode as the sole electron donor and nitrate as the electron acceptor. Nitrate was reduced to nitrite with the consumption of electrical current. The stoichiometry of electron and nitrate consumption and nitrite accumulation were consistent with the electrode serving as the sole electron donor for nitrate reduction. Analysis of 16 rRNA gene sequences demonstrated that the electrodes supplied with current were specifically enriched in microorganisms with sequences most closely related to the sequences of known Geobacter species. A pure culture of Geobacter metallireducens was shown to reduce nitrate to nitrite with the electrode as the sole electron donor with the expected stoichiometry of electron consumption. Cells attached to the electrode appeared to be responsible for the nitrate reduction. Attached cells of Geobacter sulfurreducens reduced fumarate to succinate with the electrode as an electron donor. These results demonstrate for the first time that electrodes may serve as a direct electron donor for anaerobic respiration. This finding has implications for the harvesting of electricity from anaerobic sediments and the bioremediation of oxidized contaminants.

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Section: Discussionmentioning

confidence: 70%

Graphite electrodes as electron donors for anaerobic respiration

Gregory

Bond

Lovley³

2004

Environmental Microbiology

685

460

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“…Further reactor development strategies will also likely lead to increased productivities. For example, in situ electrochemical reduction of Fe 3þ (Blake et al, 1994) has succeeded in increasing Fe 2þ delivery to wild type A. ferrooxidans cells without precipitation. Cell retention techniques, such as cross flow filtration, may also be used to keep a high cell densities in the reactors which may dramatically improve the productivity of an A. ferrooxidans continuous process.…”

Section: Discussionmentioning

confidence: 99%

Enhancing isobutyric acid production from engineered Acidithiobacillus ferrooxidans cells via media optimization

West²,

Banta³

2015

Biotech & Bioengineering

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The chemolithoautotrophic bacterium Acidithiobacillus ferrooxidans has previously been genetically modified to produce isobutyric acid (IBA) from carbon dioxide while obtaining energy from the oxidation of ferrous iron. Here, a combinatorial approach was used to explore the influence of medium composition in both batch and chemostat cultures in order to improve IBA yields (g IBA/mol Fe(2+)) and productivities (g IBA/L/d). Medium pH, ferrous concentration (Fe(2+)), and inclusion of iron chelators all had positive impact on the IBA yield. In batch experiments, gluconate was found to be a superior iron chelator because its use resulted in smaller excursions in pH. In batch cultures, IBA yields decreased linearly with increases in the final effective Fe(3+) concentrations. Chemostat cultures followed similar trends as observed in batch cultures. Specific cellular productivities were found to be a function of the steady state ORP (Oxidation-reduction potential) of the growth medium, which is primarily determined by the Fe(3+) to Fe(2+) ratio. By operating at low ORP, chemostat cultures were able to achieve volumetric productivities as high as 3.8 ± 0.2 mg IBA/L/d which is a 14-fold increase over the previously reported value.

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“…Because there is no need to add Fe(II) ions during electrochemical cultivation, the concentrations of Fe(II) and Fe(III) are kept low, and inhibition of growth is minimized. The most recent report regarding electrochemical cultivation of T. ferrooxidans indicated that cell densities of 9.5 × 10 9 cells/mL were obtained, which corresponds to a 50-100-fold increase in yield over conventional batch cultivation (Blake et al, 1994). However, when grown by electrolytic cultivation, cell numbers did not increase logarithmically, and it required longer periods of time to achieve the reported high cell densities.…”

Section: Introductionmentioning

confidence: 96%

Extension of logarithmic growth of Thiobacillus ferrooxidans by potential controlled electrochemical reduction of Fe(III)

Matsumoto

Nakasono

Ohmura

et al. 1999

Biotechnol. Bioeng.

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In this study, we demonstrated that the period of logarithmic growth for Thiobacillus ferrooxidans could be extended when optimal conditions for cell growth were maintained using potential controlled electrochemical cultivation with sufficient aeration. The optimal pH and Fe(II) concentration for the electrolytic cultivation were determined to be 2.0 and 150 mM, respectively. When the potential was set to 0.0V vs Ag/AgCl, the Pt electrode reduced Fe(III) to Fe(II) with an efficiency of 95%. A porous glass microbubble generator was used to maintain adequate levels of dissolved oxygen, which was the electron acceptor for T. ferrooxidans when the cell density in the medium was high. Under these conditions, cells at an initial density of 10(7) cells/mL grew logarithmically for 4days until the cell density was 4 x 10(9) cells/mL. This corresponded to a period of logarithmic growth that was 3 times longer than was observed in batch cultures without electrolysis. In addition, the final cell density reached 10(10) cells/mL after 6 days of electrochemical cultivation, which was a 50-fold increase over conventional batch culture. Under conditions of increasing cell density, potentiostatic electrolysis made it possible to remove Fe(III), which causes product inhibition, at an increasing rate and to correspondingly increase the production rate of Fe(II), which is the electron donor for T. ferrooxidans. Thus, our cultivation system provides a sufficient supply of electron donor and acceptor for T. ferrooxidans, thereby elongating the period of logarithmic growth and producing very high cell densities.

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Enhanced Yields of Iron-Oxidizing Bacteria by In Situ Electrochemical Reduction of Soluble Iron in the Growth Medium

Cited by 51 publications

References 25 publications

Graphite electrodes as electron donors for anaerobic respiration

Graphite electrodes as electron donors for anaerobic respiration

Enhancing isobutyric acid production from engineered Acidithiobacillus ferrooxidans cells via media optimization

Extension of logarithmic growth of Thiobacillus ferrooxidans by potential controlled electrochemical reduction of Fe(III)

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