Biology subjects

Barstow, B.

Publications and source records attributed to Barstow, B..

17 recordsLinked to original sources

bioRxiv2026

Thermodynamic, Electrochemical and Practical Constraints on Electromicrobial Formate Assimilation

Electromicrobial production (EMP) technologies aim to combine renewable electricity, CO2, and engineered microbes to make energy-dense molecules at efficiencies exceeding photosynthesis. CO2 can be electrochemically reduced to formate, which is far easier to handle at the bench than H2 or an electrode, but formate carries only two electrons per carbon against the six in a biofuel. The remaining electrons must come from oxidizing additional formate, from H2 oxidation, or from extracellular electron uptake (EEU), and no rigorous comparison of these options coupled to the choice of carbon assimilation pathway currently exists. We calculate upper-limit efficiencies for butanol production by six carbon assimilation pathways, each paired with all three electron delivery mechanisms, using electrochemical parameters drawn from a survey of the recent literature. Electrical to butanol energy conversion efficiencies range from 35.5 to 51.7%, corresponding to solar-to-fuel efficiencies of 11.7 to 17%, so even the least efficient route exceeds the 8% theoretical ceiling of algal photosynthesis. The serine variant of the reductive glycine pathway reaches an electrical energy conversion efficiency of when using H2 oxidation, within 1.9 points of the most efficient pathway, and is the only high-efficiency option that tolerates O2. This makes an EMP system that combines electron delivery by formate coupled with the serine variant of reductive glycine pathway highly attractive, as it presents few barriers to rapid, iterative engineering in the lab, and a high theoretical ceiling. Drawing both carbon and electrons from formate costs 6.2 points against H2 at a state-of-the-art whole-cell voltage (2.2 V). However, this small penalty is amplified three-fold by any rise in the CO2-to-formate cell voltage, and reaches 13.5 points at the highest whole-cell voltages reported for scaled-up CO2-to-formate electrolyzers, where formate-only operation falls to 11.2 electrical-to-fuel and 3.7% solar-to-fuel efficiency, below the ceiling of photosynthesis, against 24.7 and 8.1% for H2 (only just above algal photosynthesis). Our choice between a formate-only system and one coupled to H2 oxidation or EEU therefore depends on our belief about the trajectory of CO2 reduction technology. If whole-cell voltages continue to fall at the rate of the past decade, formate alone is the right target, and the simplicity of its workflow is bought at low cost. However, if that improvement plateaus, the electron delivery mechanism must be swappable, and a system should be designed from the outset so that it can be. At the US Department of Energy SunShot target of 2 cents per kilowatt hour, the electricity to make a US gallon of butanol costs $1.40 for a formate-only system at the state of the art, rising to $5.45 at the highest scaled-up electrolyzer voltage reported, against $1.23 and $2.47 for formate and H2 system.

synthetic biology↗

bioRxiv2024

Bio-Accelerated Weathering of Ultramafic Minerals with Gluconobacter oxydans

Ultramafic rocks are an abundant source of cations for CO2 mineralization (e.g., Mg) and elements for sustainability technologies (e.g., Ni, Cr, Mn, Co, Al). However, there is no industrially useful process for dissolving ultramafic materials to release cations for CO2 sequestration or mining them for energy-critical elements. Weathering of ultramafic rocks by rainwater, release of metal cations, and subsequent CO2 mineralization already naturally sequesters CO2 from the atmosphere, but this natural process will take thousands to hundreds of thousands of years to remove excess anthropogenic CO2, far too late to deal with global warming that will happen over the next century. Mechanical acceleration of weathering by grinding can accelerate cation release but is prohibitively expensive. In this article we show that gluconic acid-based lixiviants produced by the mineral-dissolving microbe Gluconobacter oxydans accelerate leaching of Mg2+ by 20x over deionized water, and that leaching of Mg, Mn, Fe, Co, and Ni further improves by 73% from 24 to 96 hours. At low pulp density (1%) the G. oxydans biolixiviant is only 6% more effective than gluconic acid. But, at 60% pulp density the G. oxydans biolixiviant is 3.2x more effective than just gluconic acid. We demonstrate that biolixiviants made with cellulosic hydrolysate are not significantly worse than biolixiviants made with glucose, dramatically improving the feedstock available for bioleaching. Finally, we demonstrate that we can reduce the number of carbon atoms in the biolixiviant feedstock (e.g., glucose or cellulosic hydrolysate) needed to release one Mg2+ ion and mineralize one atom of carbon from CO2 from 525 to 1.

bioengineering↗

bioRxiv2024

Cross-species Comparison of Ultramafic Rock Bio-accelerated Weathering Performance

Carbon mineralization is a natural process that sequesters atmospheric CO2 by reacting it with cations (e.g., Mg2+, Ca2+) released by weathering of rocks to form solid carbonates. However, this process is too slow to capture the excess CO2 resulting from anthropogenic emissions in time to prevent significant warming of the atmosphere1-3. Additionally, accelerating carbon mineralization process by chemical or mechanical methods has proven prohibitively expensive to date4. Microbial rock-dissolution processes, including acidolysis, redoxolysis, and complexolysis, have the potential to accelerate weathering with low energy input5. However, there is no industrially useful microbe capable of dissolving ultramafic (rich in ferromagnesian minerals) rocks, suggesting that one will need to be discovered or built with synthetic biology. While microbes are known to dissolve ultramafic minerals6,7, the performance envelopes for these processes remain uncharacterized, and significant gaps exist in our knowledge of microbe-mineral interaction processes. Here, we make a normalized performance comparison of the dissolution of the ultramafic rock dunite (> 90% olivine ((Mg, Fe)2SiO4)) by three well-known mineral-dissolving microbes: Gluconobacter oxydans7-9, Sphingomonas desiccabilis10,11, and Penicillium simplicissimum12-14. We show that G. oxydans outperformed P. simplicissimum and S. desiccabilis, producing the most acidic biolixiviant (pH 2.15 when leaching 1% pulp density), and extracting the most magnesium (3,130 mg/L when leaching at 3% pulp density). Additionally, G. oxydans co-dissolves nine other metals, eight of which are critical for energy technologies (Cr, Mn, Co, Ni, Cu, and Zn)15,16 with a maximum dissolved concentration of 33 mg/L for Ni. While increasing the pulp density of the dunite (solid to liquid ratio) resulted in higher metal dissolution by G. oxydans and S. desiccabilis, notably pulp densities above 2% inhibited mineral dissolution by P. simplicissimum. Our results provide evidence that the gap in performance between G. oxydans and the other two microbes increases with pulp density, and thus, G. oxydans is best suited for process and genetic engineering to maximize performance and minimize costs and environmental impacts of bio-accelerated weathering. Finally, we propose that G. oxydans and P. simplicissimum can use cellulosic hydrolysate as a cost-effective substitute for glucose for biolixiviant production.

bioengineering↗

bioRxiv2024

Direct Genome-Scale Screening of Gluconobacter oxydans B58 for Rare Earth Element Bioleaching

The transition to a sustainable energy economy will require an enormous increase in the supply of rare earth elements (REE). Bioleaching offers a promising alternative to conventional hydrometallurgical methods for REE extraction from low-grade ores. However, exploiting this potential remains challenging due to large gaps in our understanding of the genetics involved, and inadequate biological tools to address them. We generated a highly non-redundant whole genome knockout collection for the bioleaching microbe Gluconobacter oxydans B58, reducing redundancy by 85% compared to the previous best collection. This new collection was directly screened for bioleaching neodymium from a synthetic monazite powder, identifying 89 genes important for bioleaching, 68 of which have not previously been associated with this mechanism. We conducted bench-scale experiments to validate the extraction efficiency of promising strains: 8 demonstrated significant increases in bioleaching by up to 111% (G. oxydans {delta}GO_1598, a disruption of the gene encoding the orotate phosphoribosyltransferase enzyme PyrE), and one strain significantly reduced it by 97% ({delta}GO_1096, a disruption of the gene encoding the GTP-binding protein TypA). Notable changes in biolixiviant pH were only observed for 3 strains, suggesting an important role for non-acid mechanisms in bioleaching. These findings provide valuable insights into further enhancing REE-bioleaching by G. oxydans through targeted genetic engineering.

synthetic biology↗

bioRxiv2023

Unusual 1-3 peptidoglycan cross-links in Acetobacteriaceae are made by L,D-transpeptidases with a catalytic domain distantly related to YkuD domains

Peptidoglycan is an essential component of the bacterial cell envelope that contains glycan chains substituted by short peptide stems. Peptide stems are polymerized by D,D-transpeptidases, which make bonds between the amino acid in position 4 of a donor stem and the third residue of an acceptor stem (4-3 cross-links). Some bacterial peptidoglycans also contain 3-3 cross-links that are formed by another class of enzymes called L,D-transpeptidases. In this work, we investigate the formation of unusual bacterial 1-3 peptidoglycan cross-links. We describe a version of the PGFinder software which can identify 1-3 cross-links and report the high-resolution peptidoglycan structure of Gluconobacter oxydans (a model organism within the Acetobacteraceae family). We reveal that G. oxydans peptidoglycan contains peptide stems made of a single alanine as well as several dipeptide stems with unusual amino acids at their C-terminus. Using a Sudoku transposon library, we identified a G. oxydans mutant with a drastic reduction in 1-3 cross-links. Through complementation experiments in G. oxydans and recombinant protein production in a heterologous host, we identify an L,D-transpeptidase enzyme with a domain distantly related to the YkuD domain responsible for these non-canonical reactions. This work revisits the enzymatic capabilities of L,D-transpeptidases, a versatile family of enzymes that play a key role in bacterial peptidoglycan remodelling.

microbiology↗

bioRxiv2023

Constraints on Lanthanide Separation by Selective Biosorption

Rare Earth Elements (REE) are essential ingredients of sustainable energy technologies1-5, but separation of lanthanides is considered one of the hardest problems in chemistry today6. Biosorption, where molecules adsorb to the surface of biological materials, offers a sustainable alternative to environmentally harmful solvent extractions currently used for REE separations. The REE-biosorption capabilities of some microorganisms already allow for REE separations that under specialized conditions are competitive with solvent extractions7. Our recent work has discovered the genetic basis for REE biosorption selectivity8. However, it is unclear if the small changes to selectivity produced by changes to single genetic loci could allow biosorption to leapfrog existing REE separation technologies. In this article we present three models of lanthanide separation by biosorption and desorption. The first model shows that if a biosorbing microbe behaves as it if has a single type of binding site with small preference for one lanthanide, then the small changes in selectivity produced by changes to a single genetic locus could reduce the length of a separation process by {approx} 25%. Large multi-locus gene edits could reduce a separation process length by almost 90%. On the other hand, if the microbe contains multiple sites each with a distinct preference for an individual lanthanide, then separations become challenging and larger genetic edits would be needed to enable high purity. However, even if these large genetic edits are not possible, high purity separations could still be possible by combining multiple microbes, each with small increases in selectivity, with the first designed to enrich for the target lanthanide, while subsequent microbes are designed to remove contaminants.

synthetic biology↗

bioRxiv2023

Efficient Natural Plasmid Transformation of Vibrio natriegens Enables Zero-capital Molecular Biology

The fast-growing microbe Vibrio natriegens is capable of natural transformation where it draws DNA in from media via an active process under physiological conditions. Using an engineered strain with a genomic copy of the master competence regulator tfoX from Vibrio cholera in combination with a new minimal competence media (MCM) that uses acetate as an energy source, we demonstrate naturally competent cells which are created, transformed, and recovered entirely in the same media, without exchange or addition of new media. Cells are naturally competent to plasmids, recombination with linear DNA, and co-transformation of both to select for scarless and markerless genomic edits. The entire process is simple and inexpensive, requiring no capital equipment for an entirely room temperature process (Zero Capital protocol, 104 cfu/{micro}g), or just an incubator (High Efficiency protocol, 105-6 cfu/{micro}g). These cells retain their naturally competent state when frozen and are transformable immediately upon thawing like a typical chemical or electrochemical competent cell. Since the optimized transformation protocol requires only 50 minutes of hands-on time, and V. natriegens grows quickly even on plates, a transformation started at 9 AM yields abundant culturable single colonies by 5 PM. Further, because all stages of transformation occur in the same media, and the process can be arbitrarily scaled in volume, this natural competence strain and media could be ideal for automated directed evolution applications. As a result, naturally competent V. natriegens could compete with E. coli as an excellent chassis for low-cost and highly scalable synthetic biology.

synthetic biology↗

bioRxiv2023

Efficiency Estimates for Electromicrobial Production of Branched-chain Hydrocarbons

Electromicrobial production is a process where microorganisms use electricity as a charge and energy source for the production of complex molecules, often from starting compounds as simple as CO2. The aviation industry is in need for sustainable fuel alternatives that can meet their requirements of high-altitude performance while also meeting 21st century carbon emissions standards. The electromicrobial production of jet fuel components with CO2-derived carbon provides a unique opportunity to generate jet fuel blends that are compatible with modern engines with net-neutral carbon emissions. In this study, we analyze the pathways necessary to generate single- and multi-branched-chain hydrocarbons in vivo utilizing both extracellular electron uptake (EEU) and H2-oxidation as methods for electron delivery, the Calvin cycle for CO2-fixation and the ADO decarboxylation pathway. We find the maximum electrical-to-fuel energy conversion efficiencies for single- and multi-branched chain hydrocarbons are [Formula] and [Formula]. Utilizing this information, as well as previously collected predictions on straight-chain alkane and terpenoid biosynthesis, we calculate the efficiency of electromicrobial production of jet fuel blends containing straight-chain, branched-chain, and terpenoid components. Increasing the fraction of branched-chain alkanes in the blend from zero to 47% only lowers the electrical energy conversion efficiency from [Formula] to [Formula].

synthetic biology↗

bioRxiv2023

High Efficiency Rare Earth Element Biomining with Systems Biology Guided Engineering of Gluconobacter oxydans

The global demand for critical rare earth elements (REE) is rising1 with the increase in demand for sustainable energy technologies like wind turbines2,3, electric vehicles2,3, and high efficiency lighting4. Current processes for producing REE require high energy inputs and can produce disproportionate amounts of hazardous waste. Biological methods for REE production are a promising solution to this problem. In earlier work we identified the most important genetic mechanisms contributing to the REE-bioleaching capability of Gluconobacter oxydans B585. Here we have targeted two of these mechanisms to generate a high-efficiency bio-mining strain of G. oxydans. Disruption of the phosphate-specific transport system through a clean deletion of pstS constitutively turns on the phosphate starvation response, yielding a much more acidic biolixiviant, and increasing bioleaching by up to 30%. Coupling knockout of pstS with the over-expression of the mgdh membrane-bound glucose dehydrogenase gene, results in up to 73% improvement of REE-bioleaching.

synthetic biology↗

bioRxiv2022

Genomic Characterization of Rare Earth Binding by Shewanella oneidensis

Rare earth elements (REE) are essential ingredients of sustainable energy technologies, but separation of individual REE is one of the hardest problems in chemistry today1. Biosorption, where molecules adsorb to the surface of biological materials, offers a sustainable alternative to environmentally harmful solvent extractions currently used for separation of rare earth elements (REE). The REE-biosorption capability of some microorganisms allows for REE separations that, under specialized conditions, are already competitive with solvent extractions2, suggesting that genetic engineering could allow it to leapfrog existing technologies. To identify targets for genomic improvement we screened 3,373 mutants from the whole genome knockout collection of the known REE-biosorbing microorganism Shewanella oneidensis MR-13,4. We found 130 genes that increased biosorption of the middle REE europium, and 112 that reduced it. We verified biosorption changes from the screen for a mixed solution of three REE (La, Eu, Yb) using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) in solution conditions with a range of ionic strengths and REE concentrations. We found, among other things, that disruptions of a key regulatory component of the arc system (hptA), which regulates cellular response to anoxic environments and polysaccharide biosynthesis related genes (wbpQ, wbnJ, SO_3183) consistently increase biosorption across all our solution conditions. Our largest total biosorption change comes from our SO_4685--a capsular polysaccharide (CPS) synthesis gene--disruption which results in an up to 79% increase in biosorption and nusA--a regulatory protein--disruption which results in an up to 35% decrease in biosorption. Knockouts of glnA, pyrD, and SO_3183 increase relative biosorption affinity for ytterbium over lanthanum in multiple solution conditions tested, while many other genes we explored have more complex binding affinity changes. Taken together, these results begin to elucidate how various genes affect the membrane chemistry of S. oneidensis and offer potential targets for improving biosorption and separation of REE.

systems biology↗

bioRxiv2022

Upper Limit Efficiency Estimates for Electromicrobial Production of Drop-In Jet Fuels

Microbes which participate in extracellular electron uptake or H2 oxidation have an extraordinary ability to manufacture organic compounds using electricity as the primary source of metabolic energy. So-called electromicrobial production could be of particular value in the efficient production of hydrocarbon blends for use in aviation. Because of exacting standards for fuel energy density and the costs of new aviation infrastructure, liquid hydrocarbon fuels will be necessary for the foreseeable future, precluding direct electrification. Production of hydrocarbons using electrically-powered microbes employing fatty acid synthesis-based production of alkanes could be an efficient means to produce drop-in replacement jet fuels using renewable energy. Here, we calculate the upper limit electrical-to-energy conversion efficiency for a model jet fuel blend containing 85% straight-chain alkanes and 15% terpenoids. When using the Calvin cycle for carbon-fixation, the energy conversion efficiency is [Formula] when using extracellular electron uptake for electron delivery and [Formula] when using H2-oxidation. The efficiency of production of the jet fuel blend can be raised to [Formula] when using the Formolase formate-assimilation pathway and H2-oxidation, and to [Formula] with the Wood-Ljungdahl pathway. The production efficiency can be further raised by swapping the well-known ADO pathway for alkane termination with for the recently discovered MCH pathway. If these systems were were supplied with electricity with a maximally-efficient silicon solar photovoltaic, even the least efficient would exceed the maximum efficiency of all known forms of photosynthesis.

synthetic biology↗

bioRxiv2022

Practical and Thermodynamic Constraints on Electromicrobially-Accelerated CO2 Mineralization

By the end of the century tens of gigatonnes of CO2 will need to be removed from the atmosphere every year to maintain global temperatures. Natural weathering of ultramafic rocks and subsequent mineralization reactions can convert atmospheric CO2 into ultra-stable carbonates. But, while natural weathering will eventually draw down all excess CO2, this process will need hundreds of thousands of years to do it. The CO2 mineralization process could be accelerated by weathering ultramafic rocks with biodegradable lixiviants like organic acids. But, in this article we show that if these lixiviants are produced from cellulosic biomass, the demand created by CO2 mineralization could monopolize the worlds supply of biomass even if CO2 mineralization performance is high. In this article we demonstrate that electromicrobial production technologies (EMP) that combine renewable electricity and microbial metabolism could produce lixiviants for as little as $200 to $400 per tonne at solar electricity prices achievable within the decade. Furthermore, this allows the lixiviants needed to sequester a tonne of CO2 to be produced for less than $100, even with modest CO2 mineralization performance.

synthetic biology↗

bioRxiv2021

Thermodynamic Constraints on Electromicrobial Protein Production

Global consumption of protein is projected to double by the middle of the 21st century1. However, protein production is one of the most energy intensive and environmentally damaging parts of the food supply system today. Electromicrobial production technologies that combine renewable electricity and CO2-fixing microbial metabolism could dramatically increase the energy efficiency of commodity chemical production2-5. Here we present a molecular-scale model that sets an upper limit on the performance of any organism performing electromicrobial protein production. We show that engineered microbes that fix CO2 and N2 using reducing equivalents produced by H2-oxidation or extracellular electron uptake could produce amino acids with energy inputs as low as 64 MJ kg-1. This work provides a roadmap for development of engineered microbes that could significantly expand access to proteins produced with a low environmental footprint.

synthetic biology↗

bioRxiv2021

Gluconobacter oxydans Knockout Collection Finds Improved Rare Earth Element Extraction

Rare earth elements (REE) are critical components of our technological society and essential for renewable energy technologies. Traditional thermochemical processes to extract REE from mineral ores or recycled materials are costly and environmentally harmful1, and thus more sustainable extraction methods require exploration. Bioleaching offers a promising alternative to conventional REE extraction2-4, and is already used to extract 5% of the worlds gold, and {approx} 15% of the worlds copper supply5,6. However, the performance of REE bioleaching lags far behind thermochemical processes2,7-9. Despite this, to the best of our knowledge no genetic engineering strategies have yet been used to enhance REE bioleaching, and little is known of the genetics that confer this capability. Here we build a whole genome knockout collection for Gluconobacter oxydans B58, one of the most promising organisms for REE bioleaching10, and use it to comprehensively characterize the genomics of REE bioleaching. In total, we find 304 genes that notably alter production of G. oxydans acidic biolixiviant, including 165 that hold up under statistical comparison with wild-type. The two most impactful groups of genes involved in REE bioleaching have opposing influences on acid production and REE bioleaching. Disruption of genes underlying synthesis of the cofactor pyrroloquinoline quinone (PQQ) and the PQQ-dependent membrane-bound glucose dehydrogenase all but eliminates bioleaching. In contrast, disruption of the phosphate-specific transport system accelerates acid production and enhances bioleaching. We identified 6 disruption mutants, that increase bioleaching by at least 11%. Most significantly, disruption of pstC, encoding part of the phosphate-specific transporter, pstSCAB, enhances bioleaching by 18%. Taken together, these results give a comprehensive roadmap for engineering multiple sites in the genome of G. oxydans to further increase its bioleaching efficiency.

genomics↗

bioRxiv2021

Identification of a Pathway for Electron Uptake in Shewanella oneidensis

Extracellular electron transfer (EET) could enable electron uptake into microbial metabolism for the synthesis of complex, energy dense organic molecules from CO2 and renewable electricity1-6 . EET could do this with an efficiency comparable to H2 -oxidation7,8 but without the need for a volatile intermediate and the problems it causes for scale up9. However, naturally occurring electroactive organisms suffer from a number of technical drawbacks. Correcting these will require extensive knowledge of the genetics and mechanisms of electron uptake. To date, studies of electron uptake in electroactive microbes have focused on shared molecular machinery also used for anaerobic mineral reduction, like the Mtr EET complex in the electroactive microbe Shewanella oneidensis MR-110-14. However, this shared machinery cannot explain all features of electron uptake, hindering efforts to engineer electron uptake. To address this, we screened gene disruption mutants for 3,667 genes, representing {approx} 99% of all non-essential genes, from the S. oneidensis whole genome knockout collection using a redox dye oxidation assay as a proxy for electron uptake. Confirmation of electron uptake using electrochemical testing allowed us to identify five genes from S. oneidensis that are indispensable for electron uptake from a cathode. Knockout of each gene eliminates extracellular electron uptake, yet in 4 of the 5 cases produces no significant defect in electron donation to an anode, highlighting a distinct role for these loci in electron uptake vs. donation. This result highlights an electronic connection between aerobic and anaerobic electron transport chains that allow electrons from the reversible EET machinery to be coupled to different respiratory processes in S. oneidensis. Furthermore, we find homologs to these genes across many different genera suggesting that electron uptake by EET coupled to respiration could be a widespread phenomenon. These gene discoveries provide a foundation for studying this phenotype in exotic metal-oxidizing autotrophic microbes. Additionally, we anticipate that the characterization of these genes will allow for the genetic improvement of electron uptake in S. oneidensis; and genetically engineering electron uptake into a highly tractable host like E. coli to complement recent advances in synthetic CO2 fixation15.

systems biology↗

bioRxiv2020

Constraints on the Efficiency of Electromicrobial Production

Electromicrobial production technologies (EMP) aim to combine renewable electricity and microbial metabolism. We have constructed molecular to reactor scale models of EMP systems using H2-oxidation and extracellular electron transfer (EET). We predict the electrical-to-biofuel conversion efficiency could rise to ≥ 52% with in vivo CO2-fixation. H2 and EET-mediated EMP both need reactors with high surface areas. H2-diffusion at ambient pressure requires areas 20 to 2,000 times that of the solar photovoltaic (PV) supplying the system. Agitation can reduce this to less than the PV area, and the power needed becomes negligible when storing ≥ 1.1 megawatts. EET-mediated systems can be built that are ≤ 10 times the PV area and have minimal resistive energy losses if a conductive extracellular matrix (ECM) with a resistivity and height seen in natural conductive biofilms is used. The system area can be reduced to less than the PV area if the ECM conductivity and height are increased to those of conductive artificial polymers. Schemes that use electrochemical CO2-fixation could achieve electrical-to-fuel efficiencies of almost 50% with no complications of O2-sensitivity.Competing Interest StatementThe authors have declared no competing interest.View Full Text

synthetic biology↗

bioRxiv2019

Electrical Energy Storage with Engineered Biological Systems

The availability of renewable energy technologies is increasing dramatically across the globe thanks to their growing maturity. However, large scale electrical energy storage and retrieval will almost certainly be a required in order to raise the penetration of renewable sources into the grid. No present energy storage technology has the perfect combination of high power and energy density, low financial and environmental cost, lack of site restrictions, long cycle and calendar lifespan, easy materials availability, and fast response time. Engineered electroactive microbes could address many of the limitations of current energy storage technologies by enabling rewired carbon fixation, a process that spatially separates reactions that are normally carried out together in a photosynthetic cell and replaces the least efficient with non-biological equivalents. If successful, this could allow storage of renewable electricity through electrochemical or enzymatic fixation of carbon dioxide and subsequent storage as carbon-based energy storage molecules including hydrocarbon and non-volatile polymers at high efficiency. In this article we compile performance data on biological and non-biological component choices for rewired carbon fixation systems and identify pressing research and engineering challenges.

synthetic biology↗