Conducting shell for bacteria

June 27, 2017, Wiley
Credit: Wiley

Under anaerobic conditions, certain bacteria can produce electricity. This behavior can be exploited in microbial fuel cells, with a special focus on wastewater treatment schemes. A weak point is the dissatisfactory power density of the microbial cells. An unconventional solution is now presented by Singaporean and Chinese scientists: as reported in the journal Angewandte Chemie, they coated live, electroactive bacteria with a conducting polymer and obtained a high-performance anode for microbial fuel cells.

The history of microbial goes back to the beginning of the 20th century when scientists connected bacteria cells with electrodes to generate electricity. The principle is that, if no oxygen is present, the bacteria's metabolism changes to produce protons and electrons instead of carbon dioxide and water. These electrons can be used for current generation in an electrochemical cell. Such microbial fuel cells are currently heavily investigated for sustainable energy production and, especially, wastewater treatment. Their weak point is the . Much of the electrochemical potential of the bacteria is wasted because they do not transmit their produced electrons easily to the electrode. To make them more conductive, Qichun Zhang from Nanyang Technological University, Singapore, and his colleagues explored the idea of wrapping bacteria in a shell of electron-conducting polymers. The challenge with this is that the coated bacteria must still be viable.

The scientists relied on the polymer polypyrrole. "The modification of with polypyrrole is anticipated to improve the electrical conductivity of bacterial cells without reducing their viability," the authors explained. Iron ions were employed as "the oxidative initiator to make pyrrole monomers polymerized on the [bacterium's] surface." The organism of choice was the proteobacterium Shewanella oneidensis, which is known for its metal toleration and both aerobic and anaerobic lifestyles. Still living and active, the coated bacteria were tested for biocurrent generation with a carbon anode. Compared to their unmodified counterparts, they indeed displayed a 23 times smaller resistance (which means, enhanced conductivity), a fivefold increase in electricity generation, and a 14 times higher maximum power density of the anode in a . And if the bacteria were fed with lactate, the authors observed a pronounced current, which did not happen when uncoated bacteria were used.

Zhang's approach is a remarkable solution to the conductivity problem of a microbial anode. The authors believe that this coating scheme of live may add a new dimension to the exploration of microbial fuel cells, as well as general research on cell-surface functionalization.

Explore further: Building a better microbial fuel cell—using paper

More information: Rong-Bin Song et al, Living and Conducting: Coating Individual Bacterial Cells with In Situ Formed Polypyrrole, Angewandte Chemie International Edition (2017). DOI: 10.1002/anie.201704729

Related Stories

Building a better microbial fuel cell—using paper

February 6, 2017

The concept behind microbial fuel cells, which rely on bacteria to generate an electrical current, is more than a century old. But turning that concept into a usable tool has been a long process. Microbial fuel cells, or ...

Microbial fuel cell converts methane to electricity

May 17, 2017

Transporting methane from gas wellheads to market provides multiple opportunities for this greenhouse gas to leak into the atmosphere. Now, an international team of researchers has taken the first step in converting methane ...

Progress Toward a Biological Fuel Cell?

December 30, 2008

(PhysOrg.com) -- Biological fuel cells use enzymes or whole microorganisms as biocatalysts for the direct conversion of chemical energy to electrical energy. One type of microbial fuel cell uses anodes (positive electrodes) ...

Two bacteria better than one in cellulose-fed fuel cell

July 27, 2007

No currently known bacteria that allow termites and cows to digest cellulose, can power a microbial fuel cell and those bacteria that can produce electrical current cannot eat cellulose. But careful pairing of bacteria can ...

Recommended for you

Coffee-based colloids for direct solar absorption

March 22, 2019

Solar energy is one of the most promising resources to help reduce fossil fuel consumption and mitigate greenhouse gas emissions to power a sustainable future. Devices presently in use to convert solar energy into thermal ...

NASA instruments image fireball over Bering Sea

March 22, 2019

On Dec. 18, 2018, a large "fireball—the term used for exceptionally bright meteors that are visible over a wide area—exploded about 16 miles (26 kilometers) above the Bering Sea. The explosion unleashed an estimated 173 ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.