Exploiting membrane enzymes in biotechnology: Bioelectrocatalysis and fuel cells

Lead Research Organisation: University of Leeds
Department Name: Sch of Chemistry

Abstract

It is increasingly clear that to tackle global warming and reduce our reliance on fossil fuels, a variety of approaches are required and a combination of new technologies needs to be put into practice. Many forms of renewable energy, like solar cells and windmills, provide intermittent power and hence it is important that this energy can be stored, either in batteries or by conversion into fuels. Such storage requires conversion from electrical to chemical energy and back again, which is performed by electrocatalysts. Many important reactions in energy conversion require expensive, rare metal catalysts. A case in point is hydrogen conversion. It has been estimated that the scarcity of platinum group metals will severely limit, if not prohibit, a conversion to a hydrogen economy.

Biology is very adept in energy conversion and many reactions in metabolism and respiration convert energy. These important reactions, like hydrogen or carbon dioxide conversions, are performed by biocatalysts (i.e., enzymes) that do not rely on expensive or rare metals. However, some of these enzymes reside in biological lipid membranes, which are hydrophobic (i.e. water repellent) and this makes it difficult to employ these types of biocatalysts in technologies for energy conversion.

In this project we aim to develop new types of electrocatalysts that use membrane enzymes. Our proposed technology is based on recent results, which show that membrane enzymes could be employed as electrocatalyst if deposited on conducting (metallic) surfaces. In this project, membrane enzymes will be mixed with specific types of polymers (plastic) as we previously demonstrated that these polymers can vastly extend the lifetime of membrane biocatalysts. Finally, isolating membranes enzymes from bacteria is very expensive. Thus, in this project we will not isolate these biocatalyst, but study how crude extracts from bacteria can be used as this will greatly reduce the cost of biocatalysis.

As a proof-of-principle, we will build a fuel cell that converts hydrogen and oxygen (oxygen from air) into electricity. Such hydrogen fuel cells might, in the future, recharge your laptop, phone or other mobile devices or even power your car.

Technical Summary

Progress in biotechnology over the last two decades has greatly increased the use of biocatalyst in the industrial production of complex, pure chemicals. Advantages of biocatalysts over chemical catalyst are their (stereo)selectivity, higher turnover frequencies (TOF), 'green' as well as sustainable production and optimal activity under mild pH and temperature conditions. Fundamental reactions in energy conversion and storage are also catalysed by enzymes and many of these reside in biological lipid membranes, including enzymes active in hydrogen oxidation and evolution, carbon capture (e.g., CO2 to formate) and oxygen reduction. Membrane enzymes, however, are usually not considered for biocatalysis because of the high cost of purification and low stability in detergent environments.

This proposal aims to exploit membrane enzymes for applications in bioelectrocatalysis, in particular for bioenergy related applications such as (bio)fuel cells. A technology will be developed that builds on our recent results, which show that 'cheap-to-produce' crude membrane extracts are suitable catalyst systems and that amphiphilic polymers are able to induce an unprecedented improvement in biocatalyst stability. Our vision is that membrane enzymes exhibit properties that make them particularly suitable in electrocatalysis. The 2D nature of biomembranes and their ability to self-assemble in multilayer films naturally aligns with strategies to prepare electrocatalytic surfaces. Furthermore, the hydrophobic core of biomembranes provides an ideal environment to localise and trap hydrophobic redox mediators as many membrane enzymes have naturally evolved to exchange electrons with the quinone-pool in the membrane.

Planned Impact

This project studies the fundamental properties of hybrid polymer-biomembrane multilayers on surfaces with respect to bioelectrocatalysis. It will thus impact the scientific communities working in bioelectrochemistry, membrane biology, soft matter biophysics, surfaces and biocatalysis. The development of novel bioelectrocatalytic surfaces will furthermore impact the biotechnological and biocatalytic industries. This project also aims to develop a proof-of-principle hydrogen fuel cell, which will impact on the energy industry. The development of 'green technology' will furthermore indirectly impact on society. Public engagement activities as part of this project will more directly impact general public.

Scientific communities working in membrane biology, soft matter biophysics, surfaces and biocatalysis:
The PDRA will be trained in the various interdisciplinary aspects of soft matter biophysics and bioelectrocatalysis. Our research results will be disseminated via presentations at conferences and publications in journals, as appropriate in this field. This project also includes two collaborates in Berlin and Bochum, Germany, which will impact these groups via sharing of methods, samples and data.

Biotechnological and biocatalysis industries:
This work will enhance our understanding of crude membrane extracts and hybrid polymer-biomembrane systems and the benefits these systems provide in terms of decreased cost and increased lifetimes of biocatalysts. The applicants, funded by a BBSRC pathfinder grant, are currently in contact with the biotechnology industry for the production of crude membrane extracts for the bioenergy community (industry and academia).

Hydrogen fuel cell industry:
This work will provide insight into the feasibility of using biocatalyst in the development of enzyme-based hydrogen fuel cells. In particular, it will enhance knowledge on whether hydrogenase could compete with platinum as catalyst for hydrogen conversion. Funded by a BBSRC pathfinder grant, market and cost analysis is currently being performed to test the commercialisation potential of this technology.

General public and society:
Impact to society and general public will be two fold. Direct impact will be achieved via public engagement activities, which includes participation in science-week and similar events and the commission and exhibition of an art work related to energy conversion by biocatalysis. Indirect impact to the society will be in form of research that could enhance the use of 'green' catalyst and enzyme-based hydrogen fuel cells, which subsequently could contribute to a greater use of renewable energy and a more sustainable future.

Publications

10 25 50
 
Description Programa Institucional de Internacionalizac¸a~o (PrInt)
Amount R$ 50,000 (BRL)
Funding ID 88887.696995/2022-00 
Organisation Coordenação de Aperfeicoamento de Pessoal de Nível Superior 
Sector Public
Country Brazil
Start 11/2022 
End 04/2023
 
Title Detergent-free membrane protein reconstitution into vesicles 
Description We have developed novel methods for membrane protein reconstitution from cell expression to artificial vesicles without the use of detergents. This all-polymer approach utilises existing SMALP technology but combines it with our hybrid vesicle technology to impressive effect. SMALP to vesicle membrane transfer does not readily work with traditional liposomes. However the enhanced elasticity of hybrid vesicles lowers the energy barrier to membrane protein insertion and allows detergent-free approaches, which will benefit studies of membrane proteins that are not stable in detergents. It also speeds up reconstitution protocols compared to long detergent-mediated processes requiring long centrifugation or dialysis. 
Type Of Material Technology assay or reagent 
Year Produced 2022 
Provided To Others? Yes  
Impact This technique has improved the efficiency of our internal experimental workflows and is more adaptable to the use of additional novel membrane proteins. The publication of our new method is too recent to see tangible external impacts at this stage. 
URL https://doi.org/10.1021/acs.macromol.2c00326
 
Description MD simulations of hybrid membranes - Muniz/Muller 
Organisation Federal University of Rio Grande do Sul
Country Brazil 
Sector Academic/University 
PI Contribution We have provided experimental data to support the parameterisation of simulations and downstream interpretation of findings from simulations in respect to experimental observations of these lipid/polymer hybrid systems. We have hosted PhD student Wagner Augusto Muller for 7 months to visit and perform the simulations within our research environment and conduct some simple experimental studies alongside the simulation work.
Collaborator Contribution Prof Andre Muniz and PhD student Wagner Augusto Muller have contributed coarse grained MD simulations to understand the structure and properties of our hybrid lipid-polymer membrane systems and their interaction with integral membrane proteins.
Impact We have a draft manuscript, which we hope to submit in the coming month. This is a multidisciplinary as Muniz and Muller are from a chemical engineering/physics background, collaborating with the team in chemistry/biochemistry.
Start Year 2022
 
Description Light Night Leeds 2021 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Light Night Leeds is the UK's largest annual arts and light festival. It takes place over two nights in October. Our collaborative creative outputs with poet and short-story writer Dr Caitlin Stobie, where poems inspired by the research are written onto research images from the project were edited into a 5 minute video by Stephen Manthorp from the University of Leeds' Cultural Institute. This video was projected onto the facade of the Leeds Library in the centre of Leeds as one of the exhibitions for Light Night 2021. The event attracts a large audience from across the region to see the art and light installations positioned across the city. The video for our Blurred Lines collaboration featured research outputs from several UKRI funded projects in my group on developing artificial cells for engineering biology and medical applications of soft matter. The installation was also featured within wider Light Night media, including local TV, newspaper and online social media publicity.
Year(s) Of Engagement Activity 2021