National Science Foundation     |     Directorate for Engineering  (ENG)
Division of Chemical, Bioengineering, Environmental, & Transport Systems  (CBET)
CBET Award Achievements  (Formerly "CBET Nuggets")
Notable Accomplishments from CBET Awards
Hydrogen-Evolving Nanoparticles Derived from
Thermophilic Cyanobacterial
"Photosystem I"
Could Provide A More Efficient Means to Produce Fuel
Paul Frymier  -  University of Tennessee Knoxville

Researchers at the University of Tennessee and the Oak Ridge National Laboratory have demonstrated that photosystems from bacteria that love heat can produce hydrogen when combined with platinum metal to form nanoparticles with excellent storage stability.  This approach produces more than 20 times the energy than that produced from current processes for converting biomass to energy.  The impact of this discovery could be far reaching, providing a sustainable alternative to the petroleum-based fuels that are widely used for transportation.

Background:  Hydrogen has the potential to replace gasoline and diesel as a transportation fuel. It has the advantage of being carbon-neutral when used as fuel and when used to create electricity in a fuel cell.  It also does not create sulfur- or nitrogen-oxide compounds in tailpipe gases that cause environmental and health problems.  However, there is no significant source of molecular hydrogen on Earth.  Plants and photosynthetic microorganisms use light energy from the sun to power the creation of reduced hydrocarbons like sugars and starch.  To accomplish this process, a protein complex known as Photosystem I is used to energize electrons that enable the organisms to create sugar and other carbohydrates from sunlight and carbon dioxide.  These photosystems can also be used to create hydrogen under proper environmental conditions.  The researchers have demonstrated how these naturally occurring compounds can be used outside of the organisms to provide a highly efficient and potentially sustainable system for producing hydrogen.  This research could revolutionize the generation of fuels for transportation.

Results:  With NSF support, Principal Investigators Paul Frymier and Barry Bruce, in collaboration with Oak Ridge National Laboratory Staff Scientist Hugh O'Neill, are leading an interdisciplinary team of graduate and undergraduate students at the University of Tennessee, Knoxville to purify the large protein complex known as Photosystem I from a thermophilic cyanobacterium (a heat-loving bacterium that uses photosynthesis to produce its food, just like green plants and algae do), Thermosynechococcus elongatusAfter purifying the protein complex, they use it to produce nanoparticles capable of making hydrogen in the presence of light.  They have used two separate methods to produce the nanoparticles.  One method is based on the formation of very small platinum nanoparticles on the end of the photosystem, and the other is based on the use of a hydrogenase enzyme from the bacterium Ralstonia eutropha, which is found in the soil.
The first method uses a solution of platinum, the photosystem, another protein called cytochrome c553, and vitamin C (ascorbate).  The system is self-organizing, meaning that it automatically forms the right combination of platinum metal and the photosystem when simply exposed to light.  After the particles are formed, they are re-purified and placed in an aqueous solution with fresh ascorbate and cytochrome c553 where they now produce hydrogen when exposed to light.
The particles exhibit impressive stability when simply stored in a refrigerator for months at a time.  The particles have been shown to produce hydrogen at completely stable levels at temperatures ranging from room temperature to 55 degrees C.  Because the photosystems come from a thermophilic organism, the nanoparticles produce more hydrogen as temperature increases within this range.  For example, at 55 degrees C, the nanoparticles produce hydrogen at a rate nearly 10 times that produced at room temperature.  For comparison, the rate of hydrogen production using Photosytem I from a more common cyanobacterium (Synechocystis PCC 6803) decreases with temperatures above room temperature.  Since the more common bacterium prefers room temperature, it produces less than half the hydrogen at 55 degrees C than it does at room temperature.  Because the researchers seek to use these organisms to make fuel from solar energy, they will probably use these organisms where it is hot and prefer organisms that make more hydrogen to those that make less hydrogen when it gets hot.
The work of Drs. Frymier, Bruce, and O'Neill was recently published in the journal Nature Nanotechnology.  As part of that study, they determined that at higher temperatures, their system can produce energy at a rate over 20 times that of the current switchgrass-to-ethanol process.  In order to further improve the rate of hydrogen production in these nanoparticles, the research team has been experimenting with modifying both Photosystem I and cytochrome c553 to make these two proteins bind together more strongly.  Stronger binding would result in more rapid hydrogen production; however in cyanobacteria, these two proteins do not bind together well.  In algae, they do bind together strongly, so the researchers are taking cues from the way nature made algae to be able to "algae-fy" the proteins in cyanobacteria (see Figure 3).
The second part of their work, which involves the second method mentioned above, investigates the elimination of platinum from their system through the formation of fusion complexes between a hydrogenase enzyme and the photosystem.  In this work, the researchers are starting with the hydrogenase from Ralstonia eutropha and forming a variety of fusion proteins with Photosystem I by joining the two proteins in 12 different ways.  The fusion between Photosystem I and hydrogenase should form a new protein that is capable of both capturing light and using that light to form hydrogen.

Paul Frymier 1     Figure 1.
Production of hydrogen by platinized Photosytem I.
Electrons donated by ascorbate are transferred to Photosystem I through a c-type cytochrome to eventually reduce protons to molecular hydrogen at the site of the platinum nanoclusters.
Credit:  Barry Bruce - Biochemistry, Cellular, and Molecular Biology (BCMB) Dept; University of Tennessee, Knoxville
Paul Frymier 2     Figure 2.
Ribbon structure of cyt c6
from Chlamydomonas
compared to c553 from T. elongatus (right).
Five critical amino acids shown as space-filling.  Amino acids in the binding region that are the same in the two cytochromes are shown in green text.  Amino acids in the binding region that are different in the two cytochromes are shown in yellow text.  In this work, the differing amino acids in the structure on the left, where changed to those on the right to increase the natural binding affinity of the cytochrome for Photosystem I.
Credit:  Michael Vaughn and Natalie Myers - BCMB & Microbiology; University of Tennessee, Knoxville
Paul Frymier 3     Figure 3.
Fusion of hydrogenase to Photosystem I.
A [Ni-Fe] hydrogenase is shown in a possible configuration fused with the PsaE subunit of Photosystem I.  The hydrogenase enzyme replaces the role of the platinum catalyst in Figure 1.
Credit:  Barry D. Bruce and Michael Vaughn - BCMB & Microbiology; University of Tennessee, Knoxville

Scientific Uniqueness:  This study is the first to show that a thermophilic organism can be used to produce hydrogen at an enhanced rate compared to those at room temperature.  This work is being extended to determine if platinum-free systems based on fusions between hydrogenase and thermophilic Photosystem I exhibit the same rate enhancement at elevated temperatures.

This project addresses the NSF Strategic Outcome Goals, as described in the NSF Strategic Plan 2006-2011, as follows:
Primary Strategic Outcome Goal:      (1) Discovery:  This project has determined that the use of the photosystems from thermophilic cyanobacteria results in hydrogen-evolving nanoparticles that are stable and can be stored for long periods of time.  Field-scale systems have the potential to produce a potential transportation fuel (hydrogen) at more than 20 times the energy production rate of the best current biomass-to-energy scenarios.  Methods for generating new protein fusion complexes have been refined to allow new materials for solar energy conversion.

                                                                   (1) Discovery Categories:
                                                                           -  Biology
                                                                           -  Engineering

Secondary Strategic Outcome Goal:  (2) Learning:  This is a highly interdisciplinary project involving graduate and undergraduate students from microbiology, biochemistry, and chemical and biomolecular engineering.  Full and partial support from CBET has been provided to three graduate students for this project.  Partial support for an additional graduate student and two undergraduate students was provided by internal cost sharing and undergraduate research scholarships in support of this project.  Another graduate and two undergraduate students gave technical support to this project.  The graduate students are supported in their work by undergraduate students, who grow and harvest the cells.  The graduate students provide direct daily mentoring for the undergraduates.  Students from chemical engineering backgrounds develop skills in molecular biology by learning from the biochemistry and microbiology students.  Students from microbiology and biochemistry gain knowledge in reactor design and operation from chemical engineering students.  The PIs have been involved in community outreach by offering presentations at venues for the public.  The PIs have participated in presentations to K-12 students that discuss the application of science and engineering to the problem of generating a sustainable transportation fuel.
                                                                   (2) Learning Categories:
                                                                           -  K-12 Education
                                                                           -  Undergraduate Education and Undergraduate Student Research
                                                                           -  Graduate Education and Graduate Student Research
                                                                           -  Public Understanding of Science and Lifelong Learning
Secondary Strategic Outcome Goal:  (3) Research Infrastructure:  An important element of this project has been to refine a system for the real-time monitoring of very low concentrations of hydrogen in a large background of diluting gas.  The system used by the PIs can accurately detect hydrogen at levels on the order of 10-5 volume %.
                                                                   (3) Learning Categories:
                                                                           -  Research Resources (Infrastructure and Instrumentation)

This Award Achievement represents potentially Transformative Research:  This work has the potential to enable the creation of new bio-metallic and fusion proteins that could revolutionize methods for producing fuels and chemicals using solar energy.

The Intellectual Merit of this research:  This work has identified molecular biology and protein-metal deposition strategies that enable the use of the proteins from cyanobacteria to perform electron transfer and proton reduction at elevated rates at higher temperatures.

The Broader Impacts of this research include:
(1Broadens participation of underrepresented groups:  This work has broadened the gender diversity of engineering at the doctoral level by enabling a highly qualified woman PhD candidate to continue her research.  An additional woman undergraduate student has been recruited to the program and as a result of her research experience, is likely to attend graduate school as a PhD candidate.
(2Benefits of this research to society:  This work has the potential to enable new methods for generating a sustainable transportation fuel, that is carbon-neutral and does not generate nitrogen or sulfur oxides that cause respiratory problems and exaggerate existing respiratory conditions such as asthma.
(3Advancing discovery and understanding while promoting teaching, training, and learning:  The cross-training of the students in the disparate disciplines supports the development of a broad range of skills and knowledge.  The PIs have bi-weekly joint laboratory group meetings where the relevant literature as well as recent laboratory results are discussed so that all of the students gain a common knowledge and vocabulary that they can use in their future work to solve problems at the interface of biology and engineering.
(4Disseminaton of results to enhance scientific and technological understanding:  The work of this research group appeared in the journal Nature Nanotechnology, which has a very broad readership and high impact factor.  In addition, the PIs have given research overviews and general seminars on sustainability and energy to the public to foster an understanding of the issues involved in finding future alternatives for petroleum-based fuels.  These have included, but are not limited to, presentations to the local Rotary Club, local high school, and University Pre-Game Scholar Showcase and the Centripetals Seminar Series, which are promoted as scholarly presentations targeted to and heavily subscribed by the general population.

Areas of Emphasis (Themes) for FY 2010 Highlights included in this research project:
(1Interdisciplinary, high-risk, and potentially transformative
(2Promotes innovative energy technologies
(3Promotes greater sustainability (includes climate change) and green jobs
(4Nurtures a world-class engineering workforce and a technically literate population
(5Relates to Congressional Priority Programs:  RE-ENERGYSE (REgaining our ENERGY Science and Engineering Edge)

Program Director:
Gregory Rorrer
CBET Program Director - Energy for Sustainability
NSF Award Number:   0828615
Award Title:   SPHERE: Sustainable Photosynthetic Hydrogen Evolution Research
PI Name:    Paul Frymier
Institution Name:   University of Tennessee Knoxville
Program Element Code:   7644
CBET Award Achievement:

  FY 2010

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This Award Achievement was Updated on 8 September 2010.