Extracting renewable electric energy from bacterial groups

Researchers created tiny skyscrapers' for bacterial groups to enable them to produce electricity using only sunlight and water.

The University of Cambridge researchers used 3D printing to build grids of high-rise "nano-housing" wherein sun-loving bacteria thrive rapidly. The researchers were then managed to generate waste electrons from photosynthesis from the bacteria, that can be utilized to operate small devices.

Numerous different experiments have extracted energy from photosynthetic bacteria, but the Cambridge team discovered that offering them with the suitable type home enhances the quantity of energy they can extract by an order of magnitude. The methodology competes with traditional techniques of renewable bioenergy generation and already achieved solar conversion efficiencies that can surpass several other prevailing biofuel generation approaches.

Their findings, published in the journal Nature Materials, demonstrate that 'biohybrid' solar energy sources could contribute in the zero-carbon energy supply.

Present alternative energy sources, such as silicon-based solar cells and biofuels, are much favorable to fossil fuels in relation to carbon emissions; however, they have drawbacks, like those of dependence on mining, recycling issues, and involvement on farming and land use, one that leads to biodiversity loss.

“Our approach is a step towards making even more sustainable renewable energy devices for the future,” said Dr. Jenny Zhang from the Yusuf Hamied Department of Chemistry, who led the research.

Zhang and her associates from the Departments of Biochemistry and Materials Science and Metallurgy are rethinking bioenergy to achieve sustainability and expandability.

Photosynthetic bacteria, also known as cyanobacteria, are most prevalent type of organism on Earth. Researchers have been seeking to "re-wire" the photosynthesis processes of cyanobacteria to generate energy off them for many decades.

“There’s been a bottleneck in terms of how much energy you can actually extract from photosynthetic systems, but no one understood where the bottleneck was,” said Zhang. “Most scientists assumed that the bottleneck was on the biological side, in the bacteria, but we’ve found that a substantial bottleneck is actually on the material side.”

Cyanobacteria demand a level of sunlight to thrive, similar to the surface of a lake during the summer. The bacteria must also be tethered to electrodes in order to obtain the energy produced by photosynthesis.

The Cambridge team 3D-printed specialized electrodes made of metal oxide nanoparticles to function with cyanobacteria during photosynthesis. The electrodes were printed in the shape of a miniature city, with highly branched, tightly packed pillar structures.

Zhang's group created a printing approach that enables influence over multiple length scales, causing the structures to become highly customizable and potentially useful in a variety of disciplines.

“The electrodes have excellent light-handling properties, like a high-rise apartment with lots of windows,” said Zhang. “Cyanobacteria need something they can attach to and form a community with their neighbors. Our electrodes allow for a balance between lots of surface area and lots of light – like a glass skyscraper.”

The researchers observed that the self-assembling cyanobacteria were more effective over other existing bioenergy systems, such as biofuels, once they were in their new "wired" home. The approach caused a lot of energy extraction from photosynthesis by an order of magnitude when compared to other sources.

“I was surprised we were able to achieve the numbers we did – similar numbers have been predicted for many years, but this is the first time that these numbers have been shown experimentally,” said Zhang. “Cyanobacteria are versatile chemical factories. Our approach allows us to tap into their energy conversion pathway at an early point, which helps us understand how they carry out energy conversion so we can use their natural pathways for renewable fuel or chemical generation.”