Reducing carbon: a bacterial approach

Happy Earth week to everyone! In honor of such an occasion, I would like to present some work by researchers trying to clean up our atmosphere.

There is a host of literature that says the abundance of carbon dioxide in our atmosphere is caused by humans, and it is responsible for climate change. It is up to us then to offset our addition of gases into the atmosphere. Researchers from the Lawrence Berkeley National Laboratory have recently presented a progressive technology that converts carbon dioxide into biofuels. To do this, they are taking some hints from nature and using photosynthesis.

Plants make photosynthesis look easy. Normally it is very difficult to mimic photosynthesis because it takes far more energy for us to reduce carbon dioxide than it does for a plant. A plant uses its energy efficiently to turn carbon dioxide into many complex molecules by using a lot of intermediates. It is far harder for us to create and store these intermediates than the organisms that do it naturally.

The difficulty in engineering photosynthesis led researchers to enlist some help in the form of bacteria. Combining materials science and living organisms allows for the best of both worlds: powerful light absorption tools and the natural synthetic capabilities of the cell. The researchers used nanowires made of silicon and titanium dioxide to capture light. The wires absorb light and donate electrons to a bacteria, S. ovata, which acts as a workhorse to reduce the carbon dioxide into acetate. S. ovata works well because it is acetogenic, meaning, it can produce acetate from carbon dioxide in an anaerobic environment. At this point, they can add different types of engineered bacteria that turn acetate into Acetyl-CoA. The engineered bacteria then use the Acetyl-CoA they created to synthesize any number of valuable chemicals such as n-butanol which can be used a biofuel and polyhydroxybutyrate (PHB), a biodegradable plastic.

Hybrid technology like this is a huge step in the right direction. Converting harmful greenhouse gasses to valuable chemicals both reduces emissions and provides necessary products at seemingly no cost to the environment, other than using up water. It may appear that the efficiency of reducing carbon dioxide is low, but this is still a novel technology with plenty of room to increase its efficacy. I hope that technology like this gets the ball rolling on new ways we can at least slow down the effects humans have on the environment.

References:

Liu, C., Gallagher, J. J. et al. Nanowire-Bacteria Hybrids for Unassisted Solar Carbon Fixation to Value-Added Chemicals. NanoLetters (2015) DOI: 10.1021/acs.nanolett.5b01254

Yarris, L. "Major Advance in Artificial Photosynthesis Poses Win/Win for the Environment" Berkeley Lab News Center, April 16, 2015.

Image credits:

Both images come from Liu & Gallagher 2015 referenced above.