Bac­teria could become a future source of electricity

One of society’s greatest chal­lenges is to meet the need for renew­able and sus­tain­able energy. Interest is grow­ing around one poten­tial such energy source: bac­teria. ​“We pick up elec­trons from the bac­teri­um and trans­fer them to an elec­trode. This enables us to obtain an elec­tric­al cur­rent from the bac­teria in real time, while they are eat­ing, as it were”, explains Lo Gor­ton, pro­fess­or of chem­istry at Lund Uni­ver­sity in Sweden. ​“This study is a break­through in our under­stand­ing of extra­cel­lu­lar elec­tron trans­fer in bac­teria”, he says. Extra­cel­lu­lar elec­tron trans­fer refers to the cur­rent that bac­teria can gen­er­ate out­side their own cell. The dif­fi­culty when extract­ing the energy is to pro­duce a molecule that can get through the bacterium’s thick cell wall to retrieve the elec­trons there more effi­ciently. In the cur­rent study, the research­ers cre­ated an arti­fi­cial molecule for this pur­pose, known as a redox poly­mer. The type of bac­teria stud­ied is a com­mon intest­in­al bac­teri­um present in both anim­als and humans, Entero­coc­cus faecal­is. The res­ults of the study are valu­able not only for their poten­tial with regard to future bac­teri­al elec­tric­al energy; they also increase our under­stand­ing of how bac­teria com­mu­nic­ate with their sur­round­ings. The bac­teria them­selves prob­ably use extra­cel­lu­lar elec­tron trans­fer to com­mu­nic­ate, both with oth­er bac­teria and with molecules. ​“Elec­tron trans­fer could be of great sig­ni­fic­ance for how the bac­teria com­mu­nic­ate with vari­ous molecules and with each oth­er in our digest­ive sys­tem, but also for how nature func­tions in a broad­er per­spect­ive. It is thought today that many geo­lo­gic­al pro­cesses are bac­teria-driv­en”, says Lo Gor­ton. Under­stand­ing how bac­teria func­tion and com­mu­nic­ate is valu­able in many con­texts. For example, bac­teria and oth­er micro-organ­isms can be used to pro­duce bio­fuel, in what is known as micro­bi­al bio­fuel cells. Of par­tic­u­lar interest in an energy con­text are the pho­to­syn­thes­ising bac­teria. If they are attached to an elec­trode, they can gen­er­ate elec­tric energy when exposed to light. This has been shown by Lo Gor­ton and his col­leagues in pre­vi­ous stud­ies.
Deep­er know­ledge about bac­teria is also sig­ni­fic­ant in terms of poten­tially using them to puri­fy wastewa­ter, to pro­duce molecules that are dif­fi­cult to syn­thes­ise or to reduce car­bon diox­ide into a more usable form, for example. Source: Lund Uni­ver­sity, press release, 26.03.2019