New technology fused with photosynthetic life offers path to green energy

February 21, 2022

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 organisms 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. Graphic depicting a novel microbial electro-photosynthetic system (MEPS), which uses a genetically engineered microbe that lacks Photosystem II, and can therefore accommodate significantly high light intensities and continue photosynthetic activity. The above graphic shows a novel microbial electro-photosynthetic system (MEPS), which uses a genetically engineered microbe that lacks a protein complex known as photosystem II, and can therefore accommodate significantly high light intensities and continue photosynthetic activity without damage. Graphic by Christine Lewis Download Full Image

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 Arizona State University's Biodesign Center for Applied Structural Discovery (CASD), the Swette Center for Environmental Biotechnology (EB) and 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 the EB and professor from ASU’s School of Sustainable Engineering and the Built EnvironmentWim Vermaas from ASU’s School of Life Sciences and Global Institute of Sustainability and Innovation (GISI); Cesar Torres from EB and ASU’s School for Engineering of Matter, Transport and EnergyJustin Flory, associate director of research for the Center for Negative Carbon Emissions; and Thomas and Ana Moore, from GISI, SMS and CASD.

Some members of the research group (from left): Wim Vermaas from ASU’s School of Life Sciences and Global Institute of Sustainability and Innovation; Petra Fromme, director of the Biodesign Center for Applied Structural Discovery; Christine Lewis, lead author, with the Biodesign Swette Center for Environmental Biotechnology (EB); Justin Flory, associate director of research for the Center for Negative Carbon Emissions; and Cesar Torres from EB and ASU’s School for Engineering of Matter, Transport and Energy.

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.

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 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."

Richard Harth

Science writer, Biodesign Institute at ASU


ASU Graduate College announces 2021–22 Outstanding Faculty Mentor Awards

The 4 awardees will be honored in a virtual ceremony Feb. 28

February 21, 2022

On Feb. 28, the Graduate College will honor four Arizona State University graduate professors with Outstanding Faculty Mentor Awards. Now in their 35th year, the Outstanding Faculty Mentor Awards recognize outstanding faculty members for their service to the graduate student and postdoctoral scholar communities through mentoring excellence.

Active, committed mentors not only offer coaching, modeling and feedback in academic and career development, but provide essential psychosocial and interpersonal connection and support. Collage of portraits of four ASU faculty members who are recipients of the Graduate College Outstanding Faculty Mentor Award. The Graduate College's four Outstanding Faculty Mentor Awardees (from left): Carla Firetto, Heather Bateman, Janet Neisewander and Jeffrey Jensen. Download Full Image

“Mentors are essential to the success of graduate students in both their academic pursuits and their professional careers,” said Elizabeth Wentz, vice provost and dean of the ASU Graduate College. “Not only is faculty mentorship one of the most important parts of being a graduate faculty member, it can be one of the most rewarding.”

Nominated by their graduate student and postdoctoral mentees, awardees come from all levels of faculty — tenured, tenure-track, non-tenure-track, clinical, instructional and postdoctoral advisers. 

This year’s event will take place virtually. Register to attend the Outstanding Faculty Mentor Awards.

2021-22 Outstanding Faculty Mentors

Outstanding Postdoctoral Mentor
Jeffrey Jensen, professor, School of Life Sciences

Jensen is a population geneticist and professor in the School of Life Sciences, the Center for Evolution and Medicine, and the Center for Mechanisms of Evolution. Over the years, Jensen has mentored 22 postdoctoral scholars and numerous undergraduate and graduate researchers.

“I have had the good fortune to have recruited many talented and highly motivated lab members, and I have maintained a strong focus on mentorship and inclusion in the 12-year existence of my lab,” Jensen said.

The Jensen Lab studies theoretical and computational population genetics and evolutionary genomics, with research funded by the National Institutes of Health, National Science Foundation, U.S. Department of Defense, European Research Council and Swiss NSF, and, most recently, by an NIH Established-Investigator MIRA award.

Parul Johri, a postdoc who has worked in Jensen’s lab for the past three years and is one of his mentees, highlights Jensen’s investment in the future of his students. She notes that he provides thorough and constructive feedback and has been a constant source of motivation and support throughout her job application process.

“I have never seen a better mentor throughout my academic career,” Johri said. 

Jensen earned bachelor’s degrees in ecology and evolutionary biology and biological anthropology from the University of Arizona. He earned his PhD in genetics at Cornell University and went on to conduct postdoctoral research as a National Science Foundation Fellow at the University of California at San Diego and the University of California at Berkeley. 

Throughout his studies, Jensen was mentored by many prominent researchers in the field of evolution, including Charles Aquadro, Doris Bachtrog, Brian Charlesworth and Rasmus Nielsen. In turn, he recognizes the importance of mentorship and hopes to inspire and guide his mentees, just as his mentors did for him.

Outstanding Master’s Mentor
Heather Bateman, associate professor, College of Integrative Sciences and Arts

Bateman is a field ecologist and conservation biologist with research interests in wildlife responses to habitat alteration, with a particular focus on amphibians, reptiles and birds. In addition to teaching herpetology and ornithology at ASU, Bateman mentors undergraduate and graduate students in wildlife ecology. 

“Heather is a well-rounded and supportive adviser who goes out of her way to make the college experience great for her undergraduate and graduate students,” said Brett Montgomery, one of Bateman’s mentees.

Montgomery was a student in Bateman’s lab as an undergrad at ASU and, six years later, is completing a master’s degree under Bateman’s supervision through a sponsored project. He said Bateman is always willing to help with navigating “the tricky terrain of academia.”

Bateman recognizes that graduate school can be very stressful but also notes that it can be a time of great joy.

“As wildlife ecologists, we work in some of the most inspiring outdoor settings, studying fascinating and rare organisms,” said Bateman. “You never forget the first time you see a Gila monster in the wild or experience monsoon storms on a summer camping trip!”

Bateman has a bachelor’s degree in ecology from Idaho State University, a master’s degree in biology from Eastern Washington University and a PhD in biology from the University of New Mexico.

Outstanding Instructional Faculty Mentor
Carla Firetto, assistant professor, Mary Lou Fulton Teachers College

Firetto is an assistant professor of education psychology in the division of teacher preparation in the Mary Lou Fulton Teachers College. Her research aims to facilitate learners’ high-level comprehension of complex texts and content through the use of small-group discussions. Firetto’s passion for teaching and education has shaped her approach to mentoring.

“A constant across all of my mentoring relationships, from undergraduate students to postdoctoral scholars, is my goal to better prepare those I mentor to think deeply and critically, which can ultimately serve them academically as well as professionally and personally,” Firetto said.

Emily Starrett, one of Firetto’s mentees, said Firetto has given guidance on narrowing her focus for future research and career paths. Starrett is currently doing an independent study with Firetto to gain experience teaching an online undergraduate course. 

“All of this work, along with the support she is giving me as my doctoral adviser, is helping guide me toward a successful academic career,” Starrett said. 

Firetto earned bachelor’s degrees in psychology and sociology from Thiel College, a master’s degree in educational psychology from the Pennsylvania State University and a PhD in educational psychology, also from the Pennsylvania State University. 

Outstanding Doctoral Mentor
Janet Neisewander, professor, School of Life Sciences

Neisewander is a behavioral neuroscientist who uses animal models to study mechanisms of drug abuse, primarily focusing on cocaine and nicotine. She has been teaching at ASU for over 20 years and has mentored numerous undergraduate and graduate students. 

Neisewander is a passionate, thoughtful and supportive mentor, according to Mark Namba, a neuroscience PhD candidate and one of her mentees. 

“I have never felt more welcomed in science than I have being in Dr. Neisewnader’s lab,” Namba said. “Dr. Neisewander has a unique way of making everyone in the room feel heard, seen and respected by always listening to her trainees and making sure their needs are met.”

Namba describes Neisewander as an “unwavering supporter of (his) career,” and since joining her lab, he says his graduate career has flourished. 

Neisewander earned bachelor’s degrees in biology and psychology from Rockford University, a PhD in behavioral and neural studies from the University of Kentucky. She also completed a postdoctoral fellowship at the University of Pennsylvania School of Medicine. She is grateful for the mentors she had throughout her academic journey. 

“I deeply appreciate that my mentors unselfishly helped me to grow professionally and personally,” said Neisewander. “The ability to serve my graduate students in a similar capacity is powerfully rewarding. Our mutual growth, accomplishments and even disappointments allow us to form bonds that carry forward beyond their days at ASU.”

Join the Graduate College in celebrating the 2021-22 Outstanding Faculty Mentors. Register for the virtual reception today.

Written by Jenna Nabors