Biofuel research could result in alternative energy source

  • Published
  • By Molly Lachance
  • Air Force Office of Scientific Research Public Affairs
Air Force-funded biofuel researchers are investigating ways to produce large quantities of hydrogen gas using photosynthetic microbes, commonly known as algae and cyanobacteria. In large quantities, the hydrogen gas could function as a renewable, cheap and clean energy source for future military systems.

Dr. Charles Dismukes of Princeton University leads the program. It includes researchers from eight different colleges and universities, known collectively as the BioSolarH2 team.

Air Force Office of Scientific Research officials fund the BioSolarH2 team as a part of the Multidisciplinary University Research Initiative, which focuses on research efforts that combine traditional science and engineering disciplines to address issues of importance to the Department of Defense.

The purpose of this research is to screen, study and genetically engineer microbes that can use light energy to split water and produce hydrogen in the presence of oxygen.

"Algae and cyanobacteria use either a direct or indirect process to make hydrogen, but in both cases they can only do so in the partial or complete absence of oxygen gas," Dr. Dismukes explained.

While screening, the BioSoloarH2 team looks for naturally-occurring, photosynthetic microbes whose hydrogen-generating enzymes, or hydrogenases, are more tolerant of oxygen.

Team members have identified several good candidate microbes from the volcanic soda lakes of the Rift Valley in East Africa, the Great Salt Lake and Yellowstone National Park.

"A key discovery has been the identification of cyanobacteria that have much higher metabolic rates of hydrogen production arising from the need to regenerate cellular energy for survival in these harsh environments," Dr. Dismukes said.

The next step is studying the metabolic pathways, or series of chemical reactions, that take place in the microbes to produce hydrogen gas.

The team has developed powerful fluorescence and electrochemical tools and bioreactors to measure the products and intermediate steps of these chemical reactions.

The BioSolarH2 team also is using multiple strategies to manipulate the chemical reactions for increased hydrogen production. One approach involves applying environmental stresses, such as osmotic shock via salt dilution, to accelerate the slow fermentation process so it better matches the daily cycle of the sun. This strategy increases the rate of hydrogen production to 20 times the normal rate.

"A newer approach involves knocking out the genes for hydrogenase-competing enzymes that consume the organic precursors essential to hydrogen production," said Dr. Walter Kozumbo, AFOSR program manager. "This approach showed promise in its first trial with a twofold increase in hydrogen generation."

Air Force officials say that eventual applications resulting from this research may include biomimetic models for engineering synthetic generators that produce molecular hydrogen from water and light. Such a capability would produce clean energy that could lead to greater independence from fossil fuels.