Carbon-Eating Bacteria Could Be One Answer to Climate Change

The bacterium Clostridium thermocellum has garnered a lot of interest recently because of its ability to break down cellulose (a notoriously tough organic compound found in plants) into usable biofuels without added enzymes.  While studying these useful properties, however, scientists at the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) made another eye opening discovery:  the bacterium can take up and metabolize carbon dioxide (CO2) as well.

This is really exciting:  although it doesn’t mean that the bacterium could “scrub” the air of CO2, it could be engineered to create more efficient biofuels that are “carbon neutral,” meaning they absorb as much CO2 as they emit.  The findings are published in Proceedings of the National Academy of Sciences.

"If we can understand the mechanism of why and how [the bacteria takes up CO2],” NREL staff scientist and co-author Katherine J. Chou told Motherboard in a phone call, we can “further engineer this bacteria to take up more.”  That could help reduce the amount of CO2 released into the environment, overall.

The fact that is at all possible to scientists is still something of a biological mystery.  C. thermocellum is a type of bacteria known as a heterotroph.  Heterotrophs require organic carbon molecules—like those from cellulose—to build cells and carry out their day to day duties.  These are the types of bacteria that ultimately turn carbon that has been cycling around in the living environment back into its inorganic form, CO2.  As the bacteria munch on organic carbons like glucose, they churn out CO2 as a waste byproduct.  This ultimately cuts into the maximum yield of biofuel these types of bacteria can create, and is known as carbon loss.

“This represents the loss of organic carbon that could have been used to make hydrogen and hydrocarbons,” said Chou.  She explained that It’s also cast a shadow over the legitimacy of using biofuels as a renewable energy source, even if it diversifies our energy base.  “If we constantly have to take renewable biomass and waste a third of that to CO2, is this even the right direction?”

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