Biophotovoltaics: oxygenic photosynthetic organisms in the world of bioelectrochemical systems

McCormick, Alistair J.; Bombelli, Paolo; Bradley, Robert W.; Thorne, Rebecca Jayne; Wenzel, Tobias; Howe, Christopher J.

doi:10.1039/c4ee03875d

Cited by 244 publications

(266 citation statements)

References 183 publications

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“…In the case of cyanobacteria, some authors 10,30 have suggested that exoelectrogenesis may be due to a reductive iron uptake mechanism as well. Although, proteins with the conserved ferric reductase domain have not been annotated for cyanobacteria.…”

Section: 29mentioning

confidence: 99%

Tapping into cyanobacteria electron transfer for higher exoelectrogenic activity by imposing iron limited growth

et al. 2018

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The exoelectrogenic capacity of the cyanobacterium Synechococcus elongatus PCC7942 was studied in iron limited growth in order to establish conditions favouring extracellular electron transfer in cyanobacteria for photo-bioelectricity generation. Investigation into extracellular reduction of ferricyanide by Synechococcus elongatus PCC7942 demonstrated enhanced capability for the iron limited conditions in comparison to the iron sufficient conditions. Furtheremore, the significance of pH showed that higher rates of ferricyanide reduction occurred at pH 7, with a 2.7-fold increase with respect to pH 9.5 for iron sufficient cultures and 24-fold increase for iron limited cultures. The strategy presented induced exoelectrogenesis driven mainly by photosynthesis and an estimated redirection of the 28% of electrons from photosynthetic activity was achieved by the iron limited conditions. In addition, ferricyanide reduction in the dark by iron limited cultures also presented a significant improvement, with a 6-fold increase in comparison to iron sufficient cultures. Synechococcus elongatus PCC7942 ferricyanide reduction rates are unprecedented for cyanobacteria and they are comparable to those of microalgae. The redox activity of biofilms directly on ITO-coated glass, in the absence of any artificial mediator, was also enhanced under the iron limited conditions, implying that iron limitation increased exoelectrogenesis at the outer membrane level. Cyclic voltammetry of Synechococcus elongatus PCC7942 biofilms on ITO-coated glass showed a midpoint potential around 0.22 V vs. Ag/ AgCl and iron limited biofilms had the capability to sustain currents in a saturated-like fashion. The present work proposes an iron related exoelectrogenic capacity of Synechococcus elongatus PCC7942 and sets a starting point for the study of this strain in order to improve photo-bioelectricity and darkbioelectricity generation by cyanobacteria, including more sustainable mediatorless systems.

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Section: 29mentioning

confidence: 99%

Tapping into cyanobacteria electron transfer for higher exoelectrogenic activity by imposing iron limited growth

et al. 2018

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“…3,4 Currently, there are also growing efforts to immobilize photosynthetic microorganisms onto electrodes to perform useful photoelectrochemistry. 5−7 This is because such organisms are robust, abundant, inexpensive to culture, and capable of performing energy storage/conversions, including photobioelectrogenesis (i.e., light-driven electricity production by living organisms). 8,9 …”

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confidence: 99%

Photoelectrochemistry of Photosystem II in Vitro vs in Vivo

et al. 2017

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Factors governing the photoelectrochemical output of photosynthetic microorganisms are poorly understood, and energy loss may occur due to inefficient electron transfer (ET) processes. Here, we systematically compare the photoelectrochemistry of photosystem II (PSII) protein-films to cyanobacteria biofilms to derive: (i) the losses in light-to-charge conversion efficiencies, (ii) gains in photocatalytic longevity, and (iii) insights into the ET mechanism at the biofilm interface. This study was enabled by the use of hierarchically structured electrodes, which could be tailored for high/stable loadings of PSII core complexes and Synechocystis sp. PCC 6803 cells. The mediated photocurrent densities generated by the biofilm were 2 orders of magnitude lower than those of the protein-film. This was partly attributed to a lower photocatalyst loading as the rate of mediated electron extraction from PSII in vitro is only double that of PSII in vivo. On the other hand, the biofilm exhibited much greater longevity (>5 days) than the protein-film (<6 h), with turnover numbers surpassing those of the protein-film after 2 days. The mechanism of biofilm electrogenesis is suggested to involve an intracellular redox mediator, which is released during light irradiation.

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“…While most METs incorporate heterotrophic bacteria that convert organic substrates to electrical power, the nearly limitless availability of solar energy has given rise to biophotovoltaics that generate current from oxygenic photosynthetic organisms (or parts thereof) in the absence of organic substrates 7,8 . Living photovoltaics consist of whole microorganisms, such as microalgae or cyanobacteria, that absorb light to catalyze the water-splitting reaction of oxygenic photosynthesis and transfer high-energy electrons to an anode.…”

Section: Living Photovoltaics Are Limited By Efficient Charge Tranmentioning

confidence: 99%

A synthetic biology approach to engineering living photovoltaics

Schuergers

Werlang

Ajo‐Franklin

et al. 2017

Energy Environ. Sci.

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The ability to electronically interface living cells with electron accepting scaffolds is crucial for the development of next-generation biophotovoltaic technologies. Although recent studies have focused on engineering synthetic interfaces that can maximize electronic communication between the cell and scaffold, the efficiency of such devices is limited by the low conductivity of the cell membrane. This review provides a materials science perspective on applying a complementary, synthetic biology approach to engineering membrane-electrode interfaces. It focuses on the technical challenges behind the introduction of foreign extracellular electron transfer pathways in bacterial host cells and the past and future efforts to engineer photosynthetic organisms with artificial electron-export capabilities for biophotovoltaic applications. The article highlights advances in engineering protein-based, electron-exporting conduits in a model host organism, E. coli, before reviewing state-of-the-art biophotovoltaic technologies that use both unmodified and bioengineered photosynthetic bacteria with improved electron transport capabilities. A thermodynamic analysis is used to propose an energetically feasible pathway for extracellular electron transport in engineered cyanobacteria and identify metabolic bottlenecks amenable to protein engineering techniques. Based on this analysis, an engineered photosynthetic organism expressing a foreign, protein-based electron conduit yields a maximum theoretical solar conversion efficiency of 6–10% without accounting for additional bioengineering optimizations for light-harvesting.

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Biophotovoltaics: oxygenic photosynthetic organisms in the world of bioelectrochemical systems

Abstract: In this review we focus on a specific sub-branch of light-harvesting bioelectrochemical systems called biophotovoltaic systems.

Cited by 244 publications

References 183 publications

Tapping into cyanobacteria electron transfer for higher exoelectrogenic activity by imposing iron limited growth

Tapping into cyanobacteria electron transfer for higher exoelectrogenic activity by imposing iron limited growth

Photoelectrochemistry of Photosystem II in Vitro vs in Vivo

A synthetic biology approach to engineering living photovoltaics

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