Advancing Biotechnologies for Fuel Generation: Exploiting Transmembrane Cytochromes for Solar Energy Conversion

Lead Research Organisation: University of Leeds
Department Name: Institute of Membrane & Systems Biology

Abstract

Reports concerning dwindling reserves of fossil fuels and concerns over fuel security are frequent news headlines. The rising costs of fuel are a daily reminder of the challenges faced by a global society with ever increasing energy demands. In this context it is perhaps surprising that so many of the renewable energy supplies available to us, namely, sunlight, winds and waves, remain largely untapped resources. This is mainly due to the challenges that exist in converting these energy forms into fuels from which energy can be released 'on demand' when we wish to play computer games, drive a car and so on. However, during plant photosynthesis fuels are made naturally from the energy in sunlight. Light absorption by the green chlorophyll pigments generates an energised electron that is directed, along chains of metal centres, to catalysts that make sugars. These sugars fuel us, and all animals, when their energy is released following digestion of a meal. However, using farmed plants to produce biofuels is controversial as agriculture is also required to feed the world. As a consequence, and inspired by natural processes, we propose to build a system for artificial photosynthesis. In essence, we wish to place tiny solar-panels on microbes in order to harness sunlight to drive the production of hydrogen - a fuel from which the technologies to release energy on demand are well-advanced. We will use dyes and semi-conductor particles as mechanically and chemically robust materials to capture the energy in sunlight and generate energised electrons. We will couple these particles to biology's version of conducting wires. These wires are made from heme proteins that span membranes that provide Nature's solution to compartmentalising water-filled chambers (i.e., the inside of the bacterium). The heme-wires are produced naturally by 'rock-breathing' microorganisms and after these wires have transferred the energised electrons across the membrane they will drive enzyme catalysis to produce hydrogen Our novel bio-mimetic photocatalysts will establish new principles for the design of homogeneous photocatalysts with spatially segregated sites for fuel-evolution and the supply of electrons that is needed to sustain this process. We imagine that our photocatalysts will proove versatile and that with slight modification they will be able to harness solar energy for the manufacture of drugs and fine chemicals.

Technical Summary

Most artificial homogeneous photosynthetic systems suffer a major drawback: a short-lived charge separated state, which is due to the failure to spatially decouple the reductive and the oxidative sites required to sustain charge separation. Inspired by membrane bilayers as Nature's solution to spatially decouple reduction and photoexcitation/oxidation, we propose to utilise synthetic biology to develop a novel approach that adopts the principles of natural photosynthesis; light harvesting, charge separation and catalysis. Our photocatalysts will exploit the outer-membrane spanning, cytochrome-based electron-transfer conduits produced naturally by Shewanella oneidensis MR-1. We will establish methods to attach photosensitisers, e.g., dye-sensitised TiO2 and CdS nanoparticles, to the external cytochrome of this conduit in a manner that allows for a rapid charge separation across the membrane creating a long-lived charge separated state. We will develop methods to deliver electrons from the internal face of the conduit to redox catalysts. As a proof-of-principle, the conduit will be coupled to hydrogen-evolving catalysts that will include a [NiFeSe]-hydrogenase, a synthetic cobaloxime catalyst that evolves hydrogen in pH neutral conditions, and colloidal platinum, well-known for its hydrogen evolving properties. Voltammetric and spectroscopic methods together with quantification of hydrogen evolution by gas-chromatography will define the solar conversion efficiencies, electron transfer rate and catalytic properties of these systems. Conditions will then be established to combine systems with the desired properties as hybrid photocatalysts in the bilayers of liposomes and also in S. oneidensis MR-1. Two methods will be employed to deliver the electrons required to sustain hydrogen evolution, sacrificial electron donors such as triethanolamine and electrodes. The latter is explored as it offers opportunities for simultaneous production of electricity.

Planned Impact

Societal impact

The aim of this project is to use biotechnological, biophysical, (bio)nanotechnological and synthetic biological approaches to study and exploit Shewenella sp. and Shewanella proteins. In particular, we aim to exploit Shewenalla sp. and their respiratory proteins to harvest solar energy and produce carbon-neutral fuels such as hydrogen. A renewable energy cycle is recognized as a top national strategic priority in the UK (UK White Paper on Energy). In the last 18 months, several incidents have demonstrated the fragility of the global energy supply: the sharp rise in oil prices following the outbreak of conflicts and civil wars in the Middle-East and the ecological and humanitarian threat of a nuclear meltdown in Fukushima, Japan. The search for alternative energy sources is therefore of major importance to THE GLOBAL SOCIETY. A solution to this problem has to be sought by combining a multitude of 'alternative' energy sources; this research will contribute to this progress.

A new academic partnership & training of new leaders in the energy sector

This project will establish a new academic partnership between Butt, Clarke, Richardson at Univ. East Anglia, Jeuken at Univ. Leeds and Reisner at Univ. Cambridge. The strong ties through this BBSRC project will allow us to form a nucleus around which future networks and collaborations will be built. Within this project we will also provide top-quality cross-disciplinary training for three BBSRC PDRAs, to provide expertise in the development of alternative energy biotechnologies, an area of critical scientific, technological and economic importance for the future.

Contribution to technology of alternative energy sources

Of particular interest for the studies proposed here are the multi-heme proteins in Shewanella which mediate electron transfer to the outside of the cell or to inorganic substrates. Shewanella serve as an important model system for mediator-less microbial fuel cells that run on waste carbon sources (such as in waste water) to produce electricity or hydrogen. Research into the electron transport of Shewanella will increase our understanding of their capabilities in microbial fuel cells. At this stage, these are basic research aims, with academic beneficiaries. However, after successful completion of this project, we propose that our work will contribute to the future design of such microbial fuel cells, in particular where future work aims to genetically or synthetically modify the microbes to enhance electron transfer rates to the anode (i.e., increase electrical current). Furthermore, this BBSRC proposal explores a novel and innovative approach in which the natural electron transfer pathway is reversed. Instead of generating electricity by respiring hydrogen or a carbon source, we propose to use solar energy to produce hydrogen. Although the overall concept of this proposal is the harvesting of solar energy and the storage of energy (in the form of hydrogen), the fact that electricity can be used by microbes to make 'higher-energy' organic molecules, including hydrogen and a variety of hydrocarbons, is of major economic value. Microbes as catalysts are ideal as they are relatively cheap to make and maintain (i.e., they grow and regenerate). This makes them ideal catalyst to synthesise organic molecules, such as formate, using electricity and CO2.

Publications

10 25 50
 
Description The ultimate vision in the project was to biomimic photosynthesis to make a hydrid inorganic-biological system that could (1) harvest light using nanoparticle (dye-sensitized semi-conducting nanoparticle or a quantum dot), (2) use this energy to transfer an energetis electron to redox protein MtrC), (3) rapidly transfer this electron through a lipid membrane of a liposome (via the transmembrane protein MtrCAB) and (4) transfer the electron to a catalyst that is encapsulated in the liposome to synthesize, for instance, hydrogen.

Finding show that
(1 and 2) it is possible to make hybrid system in which nanoparticles are used to harvest light and exploit this light energy to transfer an electron to a water soluble heme protein (decahemes MtrC and OmcA).
(1,2 and 3) It has furthermore been possible to expand this system and transfer electrons to a membrane complex (MtrCAB) within a liposome, such that light-induced transmembrane electron-transfer has been achieved. The latter was experimentally tested using a dye inside vesicles, which turns colourless upon reduction.
(4) We are currently incorporating hydrogen producing catalyst inside the vesicles with the ultimate aim of making a compartmentalised, light-induced hydrogen evolving catalyst.
(4) It has been shown that decaheme MtrC is very efficient in transferring electrons to other redox active proteins like fumarate reductase (FccA) and a NiFeSe hydrogenase.
Finally, it was observed, somewhat unexpectedly, that MtrC is a very active electrocatalyst for peroxide reduction, which might find applications in fuel cells (this was not an objective of the grant).
Exploitation Route Results obtained so far in this project give insight into electron transfer properties between light harvesting nanoparticles and redox proteins. These results might be used by those investigating novel or hybrid solar fuel systems. We are now incorporating hydrogen producing catalyst inside the vesicles with the aim of making a compartmentalised, light-induced hydrogen evolving catalyst.
Sectors Energy

 
Description Biohybrids for Solar Fuels: Whole-cell Photocatalysis by Non-photosynthetic Organisms
Amount £345,489 (GBP)
Funding ID BB/S000704/1 
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 01/2019 
End 12/2021
 
Description Transmembrane metallocoiled-coil proteins for compartmentalised redox catalysis
Amount £10,067 (GBP)
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 08/2015 
End 10/2015
 
Description University of Cambridge 
Organisation University of Cambridge
Department Department of Chemistry
Country United Kingdom 
Sector Academic/University 
PI Contribution This award/project is a collaboration between the University of Cambridge and the University of Leeds. All details of contributions to the project are described in detail in the proposal that led this award.
Collaborator Contribution This award/project is a collaboration between the University of Cambridge and the University of Leeds. All details of contributions to the project are described in detail in the proposal that led this award.
Impact This award/project is a collaboration between the University of Cambridge and the University of Leeds. All details of of outputs and outcomes are reported in Researchfish under this award.
Start Year 2013
 
Description University of East Anglia 
Organisation University of East Anglia
Country United Kingdom 
Sector Academic/University 
PI Contribution This award was a collaboration between us and the University of East Anglia. All details for the collaboration and research are described in detail in the research proposal.
Collaborator Contribution This award was a collaboration between us and the University of East Anglia. All details for the collaboration and research are described in detail in the research proposal.
Impact This partnership/collaborations has been funded by multiple BBSRC proposals. All outputs and outcomes are described in detail under the respective BBSRC awards.
Start Year 2009
 
Description AchiBio, the Superposition 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Other audiences
Results and Impact The Superposition is a network and space for artists, makers and scientists to collaborate. Within the superposition there are many smaller 'work groups', including BioLeeds and ArchiBio. Within ArchiBio, through an ongoing series of workshops, we are comparing architectural and biological methods and structures. The ultimate aim is create a series of exhibits and organise workshops for the general public as part of "ASMbly", (A)rt, (S)cience, (M)ake labs, which is the Superposition's annual big event. So far, the Superposition, has run 2 editions of a week long pop up art science lab with the aim of generating new artworks and prototypes in a fast, hotbed environment of cross disciplinary collaboration. These have taken place in a disused city centre spaces.
Year(s) Of Engagement Activity 2015,2016,2017
URL http://www.thesuperposition.org/portfolio-item/archibio/
 
Description Biotechnology in solar power 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Event organised by SciBar Nottingham.
Year(s) Of Engagement Activity 2016
URL http://www.meetup.com/Nottingham-SciBar/
 
Description Discovery Zone (Par of Science Week at the University of Leeds) 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? Yes
Geographic Reach Regional
Primary Audience Schools
Results and Impact It engaged school children into science in general and aims to excite them about science and science education. It also aims to raise awareness that scientist are 'normal' people, with exciting jobs.

The impact is not directly measurable, as the impact is raised awareness of and excitement towards science. However, the organisers of the discovery zone received many letters from school thanking us for a wonderful day and one of the school kids was interviewed at BBC Radio 2 about her experiences.
Year(s) Of Engagement Activity 2011,2012,2013,2014,2015,2016,2017
URL http://www.fbs.leeds.ac.uk/outreach/schools/lfos.php
 
Description Interview with science writer Clair Asher for a piece on https://howwegettonext.com/ 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Media (as a channel to the public)
Results and Impact An interview for given to Claire Asher by e-mail, who will use the material for a piece she is writing for the online magazine https://howwegettonext.com/. The final article is now published under https://howwegettonext.com/sugar-batteries-and-fake-leaves-will-light-up-your-world-ef04dace9e83.

Questions that were asked were:
1) Can you briefly explain what artificial photosynthesis is and why it is better than existing energy sources?
2) What percentage of solar energy can the latest hybrid systems capture? What challenges remain to increase that percentage further?
3) Could you explain how you've been able to combine biological and synthetic components to produce a hybrid photosynthetic system?
4) To what extent has your research been inspired by innovations in nature?
5) What breakthroughs have made this technology possible?
6) What barriers are there to artificial photosynthesis being rolled out as a source of energy?
7) How soon do you think this technology, realistically, could be in common use?
Year(s) Of Engagement Activity 2016
URL https://howwegettonext.com/sugar-batteries-and-fake-leaves-will-light-up-your-world-ef04dace9e83
 
Description Public Engagement Event on Bioenergy, connected to a symposium "Membrane Proteins From A to Z: A commemoration of the life and work of Prof. Stephen Baldwin" 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact 60 Students and their teachers participated in an event delivered by a team of our early career researchers in which they enjoyed a tour of the research facilities and a poster session on membrane related research in Leeds. At the poster session the students discussed our research with our early career researchers.

The feedback from the school clearly indicated that a major impact was to stimulate thinking and to create enthusiasm for science:

"Our students thoroughly enjoyed the chance to talk to scientists (great poster displays!), see the labs, and listen to Sir John's thought-provoking and inspiring talk. I think they felt rather special as he talked to them as the next generation with responsibilities".
Dr Kirsty Bryant Allerton High School

"It is easy to think about the highlig
Year(s) Of Engagement Activity 2015
URL http://www.fbs.leeds.ac.uk/research/bulletin/index.php?id=1495
 
Description Smallpiece nanotechnology summerschool 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact The Smallpeice Trust is an independent educational charity that organises summer schools to encourage young people to consider a career in engineering. One of their courses in Nanotechnology is held at Leeds for which we teach a short practical in microcontact printing and fluorescence microscopy. For more information, see the Smallpeice Trust webpages

The feedback from the Smallpiece Trust on our activities has been very positive. It has not been attempted to directly measure the impact (i.e. fulfilling of the aim to encourage young people to consider a career in engineering).
Year(s) Of Engagement Activity 2011,2012,2013,2014,2015
URL http://www.smallpeicetrust.org.uk/
 
Description TEDx 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? Yes
Geographic Reach International
Primary Audience Media (as a channel to the public)
Results and Impact A talk in front of a general audience was delivered in which the question was raised what biotechnology can do for solar energy harvesting. This talk was recorded and will be released under the TEDx licence on the web.

At the moment of submission (Nov. 2014) no notable impacts arose yet as the talk was only recorded on 28 October 2014 and as yet to be released.
Year(s) Of Engagement Activity 2014
URL https://www.facebook.com/tedxuniversityofleeds2014