Biotechnology: Engineered bacteria produce industrial chemicals from waste gases

Gases emitted in industrial pollution — including the greenhouse gas CO₂ — can be converted into two useful chemicals (acetone and isopropanol) using engineered bacteria, according to a study published in Nature Biotechnology. This method provides a carbon-negative alternative to current processes for manufacturing these chemicals from petroleum or natural gas.

Microbial fermentation — used in the food industry to make yogurt, beer and other products — is a promising approach for manufacturing a wide variety of chemicals from non-fossil fuel sources. Most work in this field has relied on microbes that ferment sugars; however, the use of sugars as a raw material is costly and raises the total greenhouse gas emissions of the production process. Certain bacteria, however, are capable of gas fermentation — converting gases such as CO2 into more complex molecules. This has opened up the opportunity for gases found in industrial emissions or generated from biomass and municipal waste to be turned into useful products.

Michael Köpke, Michael Jewett and colleagues show how the bacterium Clostridium autoethanogenum can be genetically engineered to synthesize chemicals it does not normally produce. The authors demonstrate the production of acetone and isopropanol — two chemicals with a combined global market of over US$10 billion — with high efficiency and selectivity in a pilot experiment at the industrial scale. Whereas existing processes for manufacturing these chemicals from petroleum or natural gas contribute to climate change, the system described by Köpke and colleagues fixes more carbon than it emits and therefore has a negative carbon footprint.

The authors suggest that their sustainable alternative for acetone and isopropanol manufacture can be adapted to produce a diverse array of other useful chemicals.