10 September 2009

More efficient bacteria can power fuel cells

In order to provide power in remote environments or to convert waste to electricity, there is a way to have bacteria generate significant amounts of electricity to power up microbial fuel cells.

Bacteria with large numbers of tiny projections called pili were more efficient at transferring electrons to generate power in fuel cells than bacteria with a smooth surface, said Professor Derek Lovley from the University of Massachusetts.

Lovley’s team isolated a strain of Geobacter sulfurreducens, which they called KN400 that grew on the graphite anodes of fuel cells. The bacteria formed a thick biofilm on the anode surface, which conducted electricity. The researchers found large quantities of pilin, a protein that makes the tiny fibers that conduct electricity through the sticky biofilm.

“The filaments form microscopic projections called pili that act as microbial nanowires,” Lovley said. “Using this bacterial strain in a fuel cell to generate electricity would greatly increase the cell’s power output.”

The pili on the bacteria’s surface seemed to be primarily for electrical conduction rather than to help them to attach to the anode; mutant forms without pili were still able to stay attached.

Microbial fuel cells have an application in monitoring devices in environments where it is difficult to replace batteries if they fail but to be successful they need to have an efficient and long-lasting source of power. In one case, Lovley said how the Geobacter sulfurreducens strain KN400 might work effectively in sensors placed on the ocean floor to monitor migration of turtles.

For related information, go to www.isa.org/manufacturing_automation.