Development of a microscopic gas diffusion-reaction model for a H2 producing biocatalyst

Providing the technology for production of renewable energy is one of the grand
challenges of this century. There are alternatives to oil, gas and nuclear such as
water, wind and solar power. Of those, the latter is a virtually unlimited power source
and we think that every effort should be undertaken to try to harvest the power
of the sun. This is not an easy task because light energy needs to
be converted into a form of energy that can be stored and supplied
on demand. A convenient storage medium are molecules comprised of atoms
that are held together by energy-rich covalent bonds. Indeed, over millions of years
nature has stored sun light in form of organic molecules (fossil fuels) via natural
photosynthesis. A carbon-free alternative storage medium is molecular hydrogen with
the added advantage that the energy density that can be stored with hydrogen
is significantly larger than for fossil fuels. Thus, molecular hydrogen is envisaged as one of
the primary energy carriers of the future. One of the grand challenges for scientists
is to find or design a cheap catalyst that allows for efficient production of hydrogen from
sunlight and a source for hydrogen atoms, ideally water.

Clearly, one of the most sustainable approaches to hydrogen production is
photocatalytic water oxidation, although this process requires efficient catalysts.
Their design is by no means trivial and can probably be considered as the holy grail
of contemporary material science. A viable alternative that we investigate here
is to exploit biological molecules (hydrogenases) that can be found in microbes
such as green algae and cyanobacteria capable of photosynthetic water splitting.
Pilot plants of H2 producing organisms exist, but there are major barriers that must
be overcome to bring the process to commercial viability. The most important one that
needs to be addressed is the high sensitivity of the organism's hydrogenase to
molecular oxygen. Evolved under anaerobic conditions, the biomolecule gets inhibited or
damaged upon exposure of the oxygen that is around us in the atmosphere.

There is evidence that hydrogenases may be modified so as to render the molecule
less sensitive to oxygen. In order to facilitate this optimization process we propose
here to investigate theoretically the primary events of the oxidative damage, that is diffusion
and binding of oxygen molecules to the active site of hydrogenases, by developing
novel molecular simulation methods. The simulations will help to understand and
interpret recent experimental measurements on a molecular level. For example,
they will allow us to understand which pathways oxygen molecules take before they
damage the active site and how fast this process occurs. The microscopic information
gained from simulation will be vital for the suggestion of modifications (mutations)
of hydrogenase that aim to restrict the access and the binding of molecular oxygen
while leaving the catalytic power for hydrogen production unchanged. The effects
of the suggested mutations will be predicted by our simulations and tested in vitro
by an experimental colleague.

The long term goal of this project is to obtain a hydrogenase mutant with
significantly increased aerotolerance, which can be used for hydrogen production
on a technological scale. This would have a tremendous socio-economic impact
as the hydrogen industry is likely to take a prominent position on the
future energy market.

The results of the research proposed will reach out to a diverse range of people and
communities including

- academics interested in fundamental and applied bioenergy research detailed in the section
'Academic Beneficiaries'.

- Users of the popular Gromacs computer simulation program, benefitting from code development
as proposed in the computational programme.

- Start-up or spin-off companies in the emerging area of biohydrogen production

- Those in the alternative energy sector with interests in exploiting microbes or hydrogenase
in biofuel cell designs

These beneficiaries will be alerted to our findings by their timely presentation at conferences, in publications and through press-releases timed to coincide with the publication of our research in leading journals. They will also gain from access to the computational and biological resources generated during the project. We anticipate that this impact will begin to be realised from month 18 of the proposed programme of research through the activities of all of the research team. To highlight our research and its potential impact to these groups we will invite representatives to a
workshop on this topic in the second half of the grant period. This conference will bring together eminent
speakers from academia and industry selected for their leading, international reputation in the area.

The work proposed will also shape the personal development of the two PDRAs. They will gain skills in
advancing computational methods and electronic structure theory under the guidance of the PIs. In addition,
the synergistic nature of the research programme and regular meetings of the research team will ensure that the PDRAs gain an understanding of the complementary approaches being used. This together with the multi-site nature of the project will ensure the PDRAs improve their skills in working collaboratively, and communicating effectively within and across sites. They will gain experience of project management under the guidance of the PIs who will also mentor their skills in oral, written and web-based communication of their findings. These impacts will begin at the outset of the project and continue to its completion.