New technology fused with photosynthetic life offers path to green
energy

Date:
February 22, 2022
Source:
Arizona State University
Summary:
Researchers have developed a patented hybrid device -- part living
organism, part bio battery, capable of producing stored energy
by increasing energy flow under light conditions where natural
photosynthesis is normally inhibited.



FULL STORY ==========================================================================
The quest for sustainable energy has become a central challenge for
society. In order to meet ever-expanding energy demands without further damaging the global climate, researchers are tapping into natural
processes that have provided plants and many animal forms with their
energy source for billions of years.

Their secret is the conversion of radiant light energy into chemical
energy in the process of photosynthesis.


==========================================================================
In new research appearing in the current issue of the Journal of the
American Chemical Society, lead author Christine Lewis and her ASU
colleagues describe a patented hybrid device -- part living organism, part
bio battery, capable of producing stored energy by increasing energy flow
under light conditions where natural photosynthesis is normally inhibited.

The advancement of such technologies offers a green pathway to the
production of a broad range of useful products, including transportation
fuels, agrochemicals, therapeutics, cosmetics, plastics and specialty
chemicals as well as human and animal supplements.

The new study shows that modified photosynthetic microbes -- in this
case, cyanobacteria -- can be fed electrons from an external source and
use these to power chemical reactions that could eventually be harnessed
for human applications. Researchers call this approach microbial electro photosynthesis or MEPS.

"This project involves unlocking the mysteries involved with energy
transfer.

Specifically, we work on bridging artificial energy with natural
photosynthesis by tapping into the latter half of the photosynthetic
electron transport chain," Lewis says. "The research objectives are
to have the ability to turn photosynthesis on at will, eventually to
make it more efficient, and produce stable energy products." Lewis is
a researcher in the Biodesign Center for Applied Structural Discovery
(CASD), Swette Center for Environmental Biotechnology (EB), and ASU's
School of Molecular Sciences (SMS).



==========================================================================
She is joined by ASU colleagues Petra Fromme, director of the Center
for Applied Structural Discovery; Bruce Rittmann, director of Swette
Center for Environmental Biotechnology and professor from ASU's School
of Sustainable Engineering and the Built Environment; Wim Vermaas from
ASU's School of Life Sciences and Julie Ann Wrigley Global Institute
of Sustainability (GIS); Cesar Torres from EB and ASU's School for
Engineering of Matter, Transport and Energy; Justin Flory, associate
director for Engineering Center for Negative Carbon Emissions and Thomas
and Anna Moore, from GIS, SMS and CASD.

Photosynthesis 2.0 The basic recipe for natural photosynthesis involves
just a few key ingredients: water, sunlight, and CO2. Photosynthetic
cells act as tiny factories for the production of glucose, which is then converted into ATP, the cell's primary energy currency. In the process,
oxygen is produced as a respiratory byproduct but can prove harmful
to the photosynthetic process when damaging oxygen radical species are
produced with high-intensity light.

Although photosynthesis is ideally suited to supplying the energy needs
of plants and other photosynthetic organisms, the rate with which light
is converted into useful chemical energy is far too low to be suitable
to supply today's human energy needs. Researchers have long sought out
ways to tap into natural photosynthesis while also improving it to find
carbon neutral energy solutions.

Partnering with nature There are several important limiting factors in
terms of energy conversion efficiency in natural photosynthesis. First, photosynthetic organisms use only a small portion of the spectrum of light emitted by the sun, namely red visible light. Second, the rate of carbon fixation is too slow for practical applications. Increasing it requires
a boost in the rate of electrons moving through the transport chain.



========================================================================== Finally, photosynthetic organisms can only deal with a limited quantity
of sun- excited electrons at one time. If the electron transport chain
is fed too many at once, the process can shut down due to light damage, disabling or killing the cell. This limitation on energy efficiency
is primarily due to a key component in the cell's electron transport
machinery, a protein complex known as photosystem II (PS II).

In the new study, the MEPS system is described using a genetically
modified cyanobacterium hitched to an external cathode. The cyanobacteria
used were reengineered in the laboratory of co-author Wim Vermaas to
carry out photosynthetic cycling of electrons without a photosystem
II component.

With the help of chemical mediators, electrons are shuttled from
the device's cathode into the electron transport chain of the
cyanobacterium. Because the light-vulnerable photosystem II has been eliminated, the photosynthetic process takes place via an alternate
pathway, namely through photosystem I.

The results verified that photosynthesis can indeed be carried out using
an external supply of electrons feeding the electron transport chain, and
it could be performed in the presence of extremely high-intensity light.

"One of my priorities as part of the team was finding the right
electrochemical mediator to move electrons into the cell," Torres said. "I think that one of the highlights was realizing we have alleviated
some of the bigger limitations of Synechocystis (cyanobacteria)
removing photosystem II for the system and giving them electrons from
an electrode." Sustainable futures The MEPS system could potentially
use currently available solar cells to provide the external electrons
needed to power photosynthetic reactions.

Photovoltaics could supply electrons from wavelengths from zero all the
way up to thousands of nanometers, providing a much broader spectrum
for light harvesting than usually available to natural photosynthesis.

The project, six years in the making, represents a melting pot of
scientific disciplines, including microbiology, engineering, biochemistry, electrochemistry, photochemistry, and physics. It has been the focus
of considerable excitement following Lewis' presentations at a variety
of conferences and her research has garnered a number of important
awards, including the 2021 North American International Society of Electrochemical Microbes Conference Best Oral Presentation Award, the
2021 Eastern Regional Photosynthetic Conference Best Poster Award, the
2019 Nature Conference Energy Award, the 2019 Gordon Research Conference
award and the 2018 Madame Curie Award at Biodesign's Fusion retreat.

"By the year 2050, with global expansion moving at the pace that it
is, our energy needs will surpass our supply. However, we can act
now to learn how to provide efficient and cleaner energy," Lewis
says. "It is my goal to contribute to the next "breakthrough"
that will help to make this big, blue marble a better place." ========================================================================== Story Source: Materials provided by Arizona_State_University. Original
written by Richard Harth. Note: Content may be edited for style and
length.


========================================================================== Journal Reference:
1. Christine M. Lewis, Justin D. Flory, Thomas A. Moore, Ana L. Moore,
Bruce
E. Rittmann, Wim F.J. Vermaas, Ce'sar I. Torres, Petra Fromme.

Electrochemically Driven Photosynthetic Electron Transport in
Cyanobacteria Lacking Photosystem II. Journal of the American
Chemical Society, 2022; DOI: 10.1021/jacs.1c09291 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220222135317.htm

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