Geobacter sulfurreducens strain engineered for increased rates of respiration

Izallalen, Mounir; Mahadevan, Radhakrishnan; Burgard, Anthony P.; Postier, Bradley L.; DiDonato, Raymond J.; Sun, Jun; Schilling, Chris; Lovley, Derek R.

doi:10.1016/j.ymben.2008.06.005

Cited by 104 publications

(88 citation statements)

References 56 publications

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“…Investigations of other pure cultures, in particular species that can derive energy and biomass from sources other than the substrate are needed in order to increase coulombic efficiencies and hydrogen recoveries. Engineering and selection of strains adapted to electron transfer to anodes may also lead to an increase in efficiencies and production rates (14,36). Furthermore, other strains that can efficiently produce hydrogen in MECs using complex substrates will help create new applications such as localized hydrogen production from diverse and abundant waste streams.…”

Section: Discussionmentioning

confidence: 99%

Hydrogen Production by Geobacter Species and a Mixed Consortium in a Microbial Electrolysis Cell

Call

Wagner

Logan

2009

Appl Environ Microbiol

187

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A hydrogen utilizing exoelectrogenic bacterium (Geobacter sulfurreducens) was compared to both a nonhydrogen oxidizer (Geobacter metallireducens) and a mixed consortium in order to compare the hydrogen production rates and hydrogen recoveries of pure and mixed cultures in microbial electrolysis cells (MECs). At an applied voltage of 0.7 V, both G. sulfurreducens and the mixed culture generated similar current densities (ca. 160 A/m 3 ), resulting in hydrogen production rates of ca. 1.9 m 3 H 2 /m 3 /day, whereas G. metallireducens exhibited lower current densities and production rates of 110 ؎ 7 A/m 3 and 1.3 ؎ 0.1 m 3 H 2 /m 3 /day, respectively. Before methane was detected in the mixed-culture MEC, the mixed consortium achieved the highest overall energy recovery (relative to both electricity and substrate energy inputs) of 82% ؎ 8% compared to G. sulfurreducens (77% ؎ 2%) and G. metallireducens (78% ؎ 5%), due to the higher coulombic efficiency of the mixed consortium. At an applied voltage of 0.4 V, methane production increased in the mixed-culture MEC and, as a result, the hydrogen recovery decreased and the overall energy recovery dropped to 38% ؎ 16% compared to 80% ؎ 5% for G. sulfurreducens and 76% ؎ 0% for G. metallireducens. Internal hydrogen recycling was confirmed since the mixed culture generated a stable current density of 31 ؎ 0 A/m 3 when fed hydrogen gas, whereas G. sulfurreducens exhibited a steady decrease in current production. Community analysis suggested that G. sulfurreducens was predominant in the mixed-culture MEC (72% of clones) despite its relative absence in the mixed-culture inoculum obtained from a microbial fuel cell reactor (2% of clones). These results demonstrate that Geobacter species are capable of obtaining similar hydrogen production rates and energy recoveries as mixed cultures in an MEC and that high coulombic efficiencies in mixed culture MECs can be attributed in part to the recycling of hydrogen into current.Electrohydrogenesis is an efficient method for generating hydrogen gas from organic matter in reactors known as microbial electrolysis cells (MECs) (17,18,26). MECs differ from air-cathode microbial fuel cells (MFCs) in that the cathode remains anaerobic, and voltage is added in order to generate hydrogen at the cathode. Under the biological conditions in MECs, hydrogen evolution is not a thermodynamically favorable reaction. However, combining the hydrogen formation reaction potential of Ϫ0.41 V at the cathode (E CAT ) with the anode potential (E AN ) typically obtained in MFCs with an E AN of Ϫ0.30 V (1 g of acetate/liter) results in a minimum required voltage of only 0.14 V. Applied voltages (E AP ) of 0.2 V (0.45 kWh/m 3 H 2 ) or larger are needed in practice to produce measurable quantities of hydrogen, but this input is substantially less than the average of 2.3 V (5.1 kWh/m 3 H 2 ) required for water electrolysis (13).Recent improvements in designs and materials have substantially improved hydrogen yields, production rates, and energy recoveries (3,18,(27)(2...

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Section: Discussionmentioning

confidence: 99%

Hydrogen Production by Geobacter Species and a Mixed Consortium in a Microbial Electrolysis Cell

Call

Wagner

Logan

2009

Appl Environ Microbiol

187

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“…Attempts to improve current production through genetic engineering have met with little success [123]. Over production of cytochromes or the microbial nanowires did not lead to an increase in power production, likewise the creation of an ATP drain, predictive by the metabolic model to increase in metabolism [124], did not increase current production.…”

Section: Electrical Interactions Between Microbes and Electrodesmentioning

confidence: 99%

Microbial Fuel Cells, A Current Review

2010

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Microbial fuel cells (MFCs) are devices that can use bacterial metabolism to produce an electrical current from a wide range organic substrates. Due to the promise of sustainable energy production from organic wastes, research has intensified in this field in the last few years. While holding great promise only a few marine sediment MFCs have been used practically, providing current for low power devices. To further improve MFC technology an understanding of the limitations and microbiology of these systems is required. Some researchers are uncovering that the greatest value of MFC technology may not be the production of electricity but the ability of electrode associated microbes to degrade wastes and toxic chemicals. We conclude that for further development of MFC applications, a greater focus on understanding the microbial processes in MFC systems is required.

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“…1.6-2.8-fold) transcript levels in the outer biofilm. Genes in the nuo cluster encode components of a large membrane-associated NADH dehydrogenase that transfers reducing equivalents generated in the TCA cycle to the menaquinone pool (Izallalen et al, 2008).…”

Section: Transcriptional Analysis Of Outer Versus Inner Members Of Cumentioning

confidence: 99%

Microtoming coupled to microarray analysis to evaluate the spatial metabolic status of Geobacter sulfurreducens biofilms

et al. 2009

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Further insight into the metabolic status of cells within anode biofilms is essential for understanding the functioning of microbial fuel cells and developing strategies to optimize their power output. Cells throughout anode biofilms of Geobacter sulfurreducens reduced the metabolic stains: 5-cyano-2,3-ditolyl tetrazolium chloride and Redox Green, suggesting metabolic activity throughout the biofilm. To compare the metabolic status of cells growing close to the anode versus cells in the outer portion of the anode biofilm, anode biofilms were encased in resin and sectioned into inner (0-20 lm from anode surface) and outer (30-60 lm) fractions. Transcriptional analysis revealed that, at a twofold threshold, 146 genes had significant (Po0.05) differences in transcript abundance between the inner and outer biofilm sections. Only 1 gene, GSU0093, a hypothetical ATP-binding cassette transporter, had significantly higher transcript abundances in the outer biofilm. Genes with lower transcript abundance in the outer biofilm included genes for ribosomal proteins and NADH dehydrogenase, suggesting lower metabolic rates. However, differences in transcript abundance were relatively low (othreefold) and the expression of genes for the tricarboxylic acid cycle enzymes was not significantly lower. Lower expression of genes involved in stress responses in the outer biofilm may reflect the development of low pH near the surface of the anode. The results of this study suggest that cells throughout the biofilm are metabolically active and can potentially contribute to current production. The microtoming/microarray strategy described here may be useful for evaluating gene expression with depth in a diversity of microbial biofilms.

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Geobacter sulfurreducens strain engineered for increased rates of respiration

Cited by 104 publications

References 56 publications

Hydrogen Production by Geobacter Species and a Mixed Consortium in a Microbial Electrolysis Cell

Hydrogen Production by Geobacter Species and a Mixed Consortium in a Microbial Electrolysis Cell

Microbial Fuel Cells, A Current Review

Microtoming coupled to microarray analysis to evaluate the spatial metabolic status of Geobacter sulfurreducens biofilms

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