In an article published in the Journal of the American Chemical Society, scientist report of purified protein extracted from Shewanella oneidensis which may be used in designing miniature bioreactor cells. These proteins --outer membrane c-type cytochrome A, or OmcA --formed a dense coating on the iron-rich mineral hematite and using a combination of techniques that included FCS, or fluorescent correlation spectroscopy, and confocal microscopy, demonstrate whether hematite was available to bind with OmcA in solution, and transfer electric charge from the protein to the mineral.

According to the reserachers, these preliminary findings suggest that these protein have the potential to be used in developing small biofuel cells.

Using pure protein opens up the possibility of shrinking biofuel cells to power small electronic devices, Squier said. Whole-organism biofuel cells require engineers to design a space-adding membrane that prevents unwanted reactions between fuel, the charge-transporting agent and the electron-accepting metal, the latter being the electrode that carries the electricity to the device. In purified protein fuel cells, the seal made by the protein coating on the electrode effectively acts in place of the membrane.

More details from the feature report from the Pacific Northwest National Laboratory.

[Photo: Artist's depiction of purified, electrified bacterial cell outer membrane protein (OmcA) binding with and passing electrons to the iron-rich mineral hematite. Source: PNNL]