By Anthony Capkun
August 11, 2016 – New research at Michigan State University shows how Geobacter bacteria grow as films on electrodes and generate electricity in a process that’s ready to be scaled up to industrial levels. Oh, they can help clean up uranium waste while they do it!
The thick biofilm is a combination of cells loaded with cytochromes, metal-based proteins and pili (hair-like protein filaments) discovered and patented by Michigan State University’s Gemma Reguera.
The biofilms are comparable to an electrical grid. Each cell is a power plant, generating electrical discharges that are delivered to the underlying electrode using a network of cytochromes and pili. The cytochromes are the transformers and towers supplying electricity to the city. The pili represent the powerlines that connect the towers, even those far away from the power plant, to the grid.
Cytochromes and pili work together for shorter ranges—the first 10 layers of cells or so closest to the electrode. As more cells stack on the electrode, the efficiency of the cytochrome as electron carrier diminishes, and the pili do all of the work, discharging electrons 1000x faster than normal.
“The pili do all of the work after the first 10 layers and allow the cells to continue to grow on the electrode—sometimes beyond 200 cell layers—while generating electricity,” said Reguera. “This is the first study to show how electrons can travel such long distances across thick biofilms; the pili are truly like powerlines, at the nanoscale.”
In their natural state, microbes have a taste for waste, Reguera added—even uranium (watch the video). Bioelectrodes also have a big appetite for waste and are ready to be scaled up and used to clean up industrial sites while producing electricity as a by-product. The next phase of this research will explore potential spinoff company options to bring the bioelectrodes to market.
— Gemma Reguera’s patented bioelectrodes have an electrifying taste for waste. Photo by Kurt Stepnitz.