Talk about having your solar powered cake and eating it, too! A researcher at UC-Berkeley has figured out that when you coat a certain kind of bacteria with nanoscale solar panels, you can get it to make biofuel, plastics and other products from sunlight, carbon dioxide and water. The process is 80% efficient, which tops natural photosynthesis, and it involves zero waste.
So, who is this mystery bacterium?
The Solar Powered Bacteria Cyborg Is Here And Its Name is Moorella
The researcher, Kelsey K. Sakimoto (working in the lab of Peidong Yang) targeted a little bug named Moorella Thermoacetica for investigation, and if you caught that “acetica” at the end then you’re on to something.
Moorella is of great interest to researchers because it converts various compounds into a useful product as it goes about its daily life. Here’s an MIT paper enthusing over the possibilities:
…Its metabolic diversity and the ability to efficiently convert a wide range of compounds, including syngas (CO + H2) into acetyl-CoA have made this thermophilic bacterium a promising host for industrial biotechnology applications.
Loosely speaking, Moorella breathes in carbon dioxide and breathes out acetic acid, a building block for other products.
Hook up Moorella with another bacteria that has a complementary metabolic system, and you have just created a bio-based factory for manufacturing fuels and plastics as well as pharmaceuticals and other useful chemicals.
Sakimoto’s research caught the CleanTechnica eye last year, when he published in the journal Science. He presented his work at the 254th National Meeting & Exposition of the American Chemical Society in Washington, DC this week (or today, if you’re reading this on August 22), and there seems to be a big buzz about it, so it’s worth taking another look.
Solar Panels For A Solar Powered Bacteria
The bio-based factory is a cool concept, especially because it has the potential to self-replicate, which means it can be a zero, or nearly zero, waste process.
One challenge is getting Moorella to go to town at a level of efficiency that provides for commercial applications.
Some researchers have been taking deep dives into the creature’s metabolism for pathways to boosting its efficiency, but Sakimoto took a hint from the field of building-integrated solar panels.
That’s where the cyborg angle comes in.
If you know what cadmium is then you’re a step ahead of everybody. For those of you new to the topic it’s a silvery white metal commonly found in zinc ore, and it pops up all over the photovoltaic field due to its high solar conversion efficiency.
Sakimoto found that when you feed cadmium to Moorella, along with an amino acid called cysteine, it will start to grow tiny particles of cadmium sulfide on its surface (the sulfide part comes from the sulfur in cysteine).
Now you have a part organic, part inorganic creature, aka a cyborg, dubbed M. thermoacetica-CdS.
In effect, the bacterium is coated with nanoscale solar panels, which explains why its efficiency climbs to 80%, which tops that of natural photosynthesis.
That’s quite a feat when you consider that naturally occurring Moorella — without the fancy solar panels — is a non-photosynthetic bacterium.
As for the commercialization angle, Sakimoto is optimistic:
“…Many current systems in artificial photosynthesis require solid electrodes, which is a huge cost. Our algal biofuels are much more attractive, as the whole CO2-to-chemical apparatus is self-contained and only requires a big vat out in the sun.”
Not for nothing but the research was funded by the US Department of Energy, so group hug for all us taxpayers.
On Beyond M. Thermoacetica-CdS
Don’t hold your breath for bacteria-produced, zero waste, carbon sequestering plastic products to line the shelves of your local online shopping logistics center any time soon — there is still a ways to go.
For one thing, Sakimoto is probably going to be logging quite a few more hours on “tweaking” the solar cells and Moorella, too.
Also, now that a mechanism for boosting the bacteria’s efficiency has been found, there is a pathway for researchers to examine other naturally occurring bacteria with similar, or even more efficient, characteristics.
That would be a good thing, because although cadmium is something of a hero in the solar energy field, it is also highly toxic, and researchers are already exploring alternative materials for high efficiency thin film solar cells.
As for the dream of a bacteria-powered world, we have practically stepped in it already.
Then there’s our personal favorite, a mud-loving bacteria called Geobacter, which produces an electrical current.
CleanTechnica began following the Geobacter research team in 2009. Some years before, they were hunting for bacteria that could be used to remediate contaminated soils, and they discovered Geobacter chomping its way through the muddy banks of the Potomac River.
The last time we checked in was back in 2014, when the team deployed electrostatic force microscopy to describe the mechanism by which Geobacter generates an electrical charge, almost like a bio-based version of a carbon nanotube. It all comes down to hairlike extensions called pili:
The new research indicates that the electron transport is based on delocalized charges, meaning that the electrons are not associated with discrete molecules. Instead, when electrons are introduced at one point, the entire pili will appear to “light up” under electrostatic force microscopy as the charge propagates along its length…
If you’re thinking that the research is leading toward power plants made up of vats of electricity-producing bacteria, ummmm…maybe.
For now it seems that the team is more interested in getting Geobacter to grow more and better pili, as a natural substitute for conventional nanowires.
Earlier this year the latest findings were featured in R&D Magazine, with this explainer from lead researcher Derek Lovley:
“…Chemically synthesizing nanowires in the lab requires toxic chemicals, high temperatures and/or expensive metals. The energy requirements are enormous. By contrast, natural microbial nanowires can be mass-produced at room temperature from inexpensive renewable feedstocks in bioreactors with much lower energy inputs. And the final product is free of toxic components.”
Image (screenshot): American Chemical Society Headline Science via YouTube.
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