My watch list
my.chemeurope.com  
Login  

Extracting energy from bacteria

31-Oct-2013

Most of us wouldn't consider bacteria a promising energy source of the future. That would be shortsighted, says Leonard Tender, a microbial-electrochemist at the Naval Research Laboratory in Washington, D.C., who believes that the focus of his research – electrode reactions catalyzed by microorganisms – may one day provide cheap, clean and abundant energy by converting the carbon dioxide in seawater to fuel and the organic matter in wastewater into electrical power.

Dissimilatory metal-reducing bacteria (DRMB) are a fascinating group of microorganisms inhabiting a wide variety of environments including marine sediments and sewage. Tender says that DRMBs acquire energy by coupling oxidation of – and the accompanying loss of electrons by – organic material with reduction of – and the gain of electrons by – insoluble oxidants such as mineral deposits. This ability, he explains, requires the bacteria to transport respired (lost) electrons to their outer surface where they become available for transfer to the insoluble oxidant. The process, known as extracellular electron transfer (EET), has been exploited by Tender and others to create a biological anode catalysts.

"For example, we can grow Geobacter sulfurreducens, a common DRMB, as a multi-cell thick biofilm on the surface of an electrode," Tender says. "Electrons are then transported by EET from the cells through the biofilm to the underlying anode surface of the electrode which results in the generation of electric current."

Just how electrons are transported through the biofilm to the anode surface over distances that can exceed 20 microns remains unsolved, Tender says. "Current evidence suggests that it occurs by incoherent multistep 'electron hopping' across a network of immobile cytochromes at the outer membrane or extracellular region, and not surprisingly, G. sulfurreducens expresses these cytochromes in both locations," he says. "We are currently studying the rate of electron flow through biofilms grown across a gap separating two electrodes—a method known as electrochemical gate measurement—and using Raman spectroscopy to monitor the oxidation state of the cytochromes in the biofilms to see if the electron hopping model is validated."

So far, Tender reports, the data indicate yes. "Our gate measurements reveal a set of highly resolved peaks in plots of current through the biofilms vs. potentials applied to the electrode representing indicative of a electron hopping from cytochrome to cytochrome," he says.

If microbial electrode catalysts can be successfully implemented in the future, Tender says, the payoff would be the ability to generate unlimited amounts of energy from the carbon dioxide in seawater and sunlight. "In theory, it could be done by using an electrode to supply electrons to a microbial biofilm that reduces CO2 to organic carbon," he says. "Once can imagine a large refinery that is solar powered, sucks in seawater or sewage, and makes fuel or electricity."

"In fact, we believe that as long as a marine or wastewater environment can continuously supply the organic material and the oxidant to the MEC, it could run almost endlessly," Tender says.

Facts, background information, dossiers
  • Naval Research Laboratory
  • American Institute…
More about American Institute of Physics
  • News

    Energy harvesting via smart materials

    Energy harvesting is emerging as a viable method for electronic devices to pull ambient energy from their surrounding environment and convert it into electrical energy for stored power. This coveted technology has the potential to serve as an alternative power supply for batteries that are ... more

    Nanodevice, build thyself

    As we continue to shrink electronic components, top-down manufacturing methods begin to approach a physical limit at the nanoscale. Rather than continue to chip away at this limit, one solution of interest involves using the bottom-up self-assembly of molecular building blocks to build nano ... more

    Sugar-based carbon hollow spheres that mimic moth eyes

    Antireflective coatings are used to cut surface glare in everything from eyeglasses and camera lenses to solar cells, TV screens and LED devices. Now researchers from Research Institute for Nuclear Problems of Belarusian State University in Belarus and Institut Jean Lamour-Université de Lor ... more

Your browser is not current. Microsoft Internet Explorer 6.0 does not support some functions on Chemie.DE