Michael Köpke and his colleagues went on a hunt for strains of the ethanol-producing bacterium, Clostridium autoethanogenum, to identify enzymes that would allow the microbes to create acetone (used to make paint and nail polish remover) and combined the genes for these enzymes into one organism. Then, they repeated this process for isopropanol, which is used as a disinfectant.
The result was an engineered bacteria that ferments carbon dioxide from the air to make these useful chemicals. “You can imagine the process similar to brewing beer,” explains Köpke. “But instead of using a yeast strain that eats sugar to make alcohol, we have a microbe that can eat carbon dioxide.”
The team scaled their initial experiments by a factor of 60 and discovered that the process locks in around 1.78 kg of carbon per kilogram of acetone produced and 1.17 kg of isopropanol. Conventionally, these chemicals are made using fossil fuels via a process that emits 2.55 kg and 1.86 kg of carbon dioxide per kilogram of acetone and isopropanol respectively.
If Köpke’s and his team’s engineered bacterium is widely adopted, then there could be a 160 percent drop in greenhouse gas emissions the researchers say. They could also make their technique even more sustainable by using waste gas from other industrial processes.
“As a population, we are looking for ways to better partner with the planet right now,” says team member Michael Jewett at Northwestern University, Illinois. “What is exciting about this work is that it really advances and applies our capacities to partner with biology, to make what’s needed when and where it’s needed on a sustainable and renewable basis.”
The team hopes that their findings can offer a blueprint for more chemicals to be produced in a carbon-negative way.
Source study: Nature Biotechnology—Carbon-negative production of acetone and isopropanol by gas fermentation at industrial pilot scale