Enhance storage and generation of electricity from renewable resources.

Engineering Biology for Climate & Sustainability

Enhance storage and generation of electricity from renewable resources.

Current State-of-the-Art

The accelerating pace at which renewable power generation capacity using wind and solar photovoltaics is being introduced presents a growing challenge: wind and solar-based power generation is inherently intermittent, necessitating that energy must be stored and delivered independently from generation. This represents a significant inefficiency in the power system, reduces revenue from renewable power generation facilities and ultimately slows the roll out of this sustainable infrastructure. The capacity of today’s batteries is not suitable for the demand of the grid and batteries rely on the mining of rare earth metals, a process that is vastly detrimental to the environment.¹ Bio-powered energy storage represents an attractive alternative to this and can help to adapt and decentralize energy availability.² Biological systems are able to store excess energy in the form of polyhydroxyalkanoates (PHAs), glycogen, and triglycerides, and then use it on demand. Some biological systems are even able to generate electricity or hydrogen gas. The inherent process of microbes to oxidize organic materials and generate electricity has led to the development of microbial fuel cells; scale up of this technology could enable remote, persistent power sources.³ This goal aims to capture potential opportunities to enhance biological energy storage and generation in order to protect from the environmental and human health impacts of current, unsustainable energy sources.

Breakthrough Capabilities & Milestones

Enable electricity production by engineered biological systems.

Improve microbial fuel cells to enhance electricity storage and generation.

Engineer biological electron transfer pathways (either in microbial or cell-free systems) that can efficiently interconvert electrons with biological reducing cofactors (e.g., NAD(P)H).

Bottleneck/Challenge: The systems biology of electron transport systems is poorly resolved for engineering purposes (see Anand et al., 2022⁴); participating proteins are known but their individual functions are not well-understood.

Potential Solution: Optimize electron transport pathways for engineering across relevant strains and systems, such that they can then be modified in concert with cofactors.

Engineer efficient metabolic and microbial electron transfer pathways to funnel biological reducing cofactors to biocathode, biofilms, or nanowires.

Develop a versatile microbial (or cell-free) electricity generation module that can efficiently couple any electrochemical oxidation reaction into electricity generation.

Bottleneck/Challenge: Extracellular electron transfer regulation mechanisms are poorly understood and highly dependent on organisms of interest.

Potential Solution: Metabolic flow analysis of different proteins on relevant microbes, using knockout systems and other genetic engineering tools.⁵

Produce and maintain stable, large scale “microbial batteries” with high capacity.

Enable biological systems to store and utilize excess electricity generated by (intermittent) renewable energy sources.

Identify, understand, and mitigate rate limiting steps in microbial extracellular electron transfer (EET).

Bottleneck/Challenge: A lack of screening methods hinders the discovery of novel electroactive microbes.

Potential Solution: Develop new high-throughput tools to screen for microbial EET activities.

Potential Solution: Engineer model chassis (e.g., E. coli) for implementation of extracellular electron transfer (EET) pathway.

Bottleneck/Challenge: Attempts to isolate electroactive microbes on non-selective media have led to the loss of electroactivity in selected microbes.

Potential Solution: ○ Potential Solution: Select microbes under anoxic environments, since most electroactive microbes are anaerobes.⁶

Demonstrate cost-effective microbial electrosynthesis (MES) systems that convert renewable electricity and CO₂ into C1 (e.g., methane; Jayathilake, 2022*) or multi-carbon molecules (e.g., alcohols).

Bottleneck/Challenge: Currently available biocatalysts have small current densities (<100 mA/cm2) that do not meet the requirements for industrial applications.

Potential Solution: Identify and engineer genetic circuits that control electron flux in electroactive microbes (e.g., Shewanella oneidensis) to increase current output.

Bottleneck/Challenge: Need to better understand the effects of operating parameters (e.g., pH, temperature, electrode potential) on the efficiency of MES systems.

Potential Solution:Measure MES system performance in a variety of operating environments, including under industrially relevant conditions.

Bottleneck/Challenge: Most MES studies focus only on acetate production,⁷ so there is a need to diversify products from MES systems.

Potential Solution:Map metabolic pathways in electroactive microbes to identify new pathways to synthesize multi-carbon molecules.

Potential Solution:Develop coupled systems that allow for efficient upgrading of acetate to a range of multi-carbon products via a secondary engineered system.⁸

Enable biological systems to produce hydrogen from renewable resources.

Develop biological electrosynthesis systems that can be directly connected to the power grid.

*Jayathilake, B. S., Chandrasekaran, S., Freyman, M. C., Deutzmann, J. S., Kracke, F., Spormann, A. M., Huang, Z., Tao, L., Pang, S. H., & Baker, S. E. (2022). Developing reactors for electrifying bio-methanation: A perspective from bio-electrochemistry. Sustainable Energy & Fuels, 6(5), 1249–1263. https://doi.org/10.1039/D1SE02041B

Footnotes

EARTH.ORG. (2020). Earth.Org – Past | Present | Future. https://earth.org/rare-earth-mining-has-devastated-chinas-environment/
Salimijazi, F., Parra, E., & Barstow, B. (2019). Electrical energy storage with engineered biological systems. Journal of Biological Engineering, 13(1), 38. https://doi.org/10.1186/s13036-019-0162-7
Kim, B. H., Chang, I. S., & Gadd, G. M. (2007). Challenges in microbial fuel cell development and operation. Applied Microbiology and Biotechnology, 76(3), 485–494. https://doi.org/10.1007/s00253-007-1027-4
Anand, A., Patel, A., Chen, K., Olson, C. A., Phaneuf, P. V., Lamoureux, C., Hefner, Y., Szubin, R., Feist, A. M., & Palsson, B. O. (2022). Laboratory evolution of synthetic electron transport system variants reveals a larger metabolic respiratory system and its plasticity. Nature Communications, 13(1), 3682. https://doi.org/10.1038/s41467-022-30877-5
Sydow, A., Krieg, T., Mayer, F., Schrader, J., & Holtmann, D. (2014). Electroactive bacteria—Molecular mechanisms and genetic tools. Applied Microbiology and Biotechnology, 98(20), 8481–8495. https://doi.org/10.1007/s00253-014-6005-z
Bar-Even, A., Noor, E., Lewis, N. E., & Milo, R. (2010). Design and analysis of synthetic carbon fixation pathways. Proceedings of the National Academy of Sciences, 107(19), 8889–8894. https://doi.org/10.1073/pnas.0907176107
Scheffen, M., Marchal, D. G., Beneyton, T., Schuller, S. K., Klose, M., Diehl, C., Lehmann, J., Pfister, P., Carrillo, M., He, H., Aslan, S., Cortina, N. S., Claus, P., Bollschweiler, D., Baret, J.-C., Schuller, J. M., Zarzycki, J., Bar-Even, A., & Erb, T. J. (2021). A new-to-nature carboxylation module to improve natural and synthetic CO₂ fixation. Nature Catalysis, 4(2), 105–115. https://do i.org/10.1038/s41929-020-00557-y
Hu, P., Chakraborty, S., Kumar, A., Woolston, B., Liu, H., Emerson, D., & Stephanopoulos, G. (2016). Integrated bioprocess for conversion of gaseous substrates to liquids. Proceedings of the National Academy of Sciences, 113(14), 3773–3778. https://doi.org/10.1073/pnas.1516867113