Using two bacteria species instead of one, a team of scientists in China have found a way to create a living energy production system that efficiently converts light to electrical energy.
AsianScientist (Oct. 4, 2019) – Researchers in China have integrated living microbes with electrical components to create a ‘bio-battery.’ They published their findings in the journal Nature Communications.
Photosynthetic microbes in nature can convert light into nutrients, which are effectively a store of energy. Researchers at the Institute of Microbiology of the Chinese Academy of Sciences questioned if there was a possibility of manipulating photosynthetic bacteria such that they could convert light into electrical power instead—what is known as a biophotovoltaic system (BPV).
BPV is more environmentally friendly and potentially more cost-effective than semiconductor-based photovoltaics (PV), given the toxicity and hard-to-recycle nature of PV materials. However, the power densities of BPV systems reported to date have been low, since photosynthetic microorganisms have a weak capacity to transfer electrons outside cells.
To circumvent this problem, the researchers created a two-species microbial consortium comprising photosynthetic cyanobacteria and the exoelectrogenic bacteria Shewanella. Exoelectrogenic bacteria have the ability to transfer electrons outside their cell bodies.
In this microbial consortium, cyanobacteria capture solar energy and fix carbon dioxide, synthesizing D-lactate. Shewanella then produce electricity by oxidizing D-lactate, thus creating a constrained electron flow from photons to D-lactate, then to electricity.
Through genetic manipulation, as well as manipulation of the growth medium and device, the two very different microorganisms worked together effectively, the researchers reported. Their BPV system generated a power density of 150 mW·m-2 in a temporal separation setup, which is approximately one order of magnitude greater than previous BPV systems.
The researchers further demonstrated that this BPV system can stably operate for more than 40 days at an average power density of 135 mW·m-2 in a spatial-temporal separation setup with medium replenishment. According to the authors, this represents the greatest longevity and power output per device of any BPV system reported to date.
