Bottle of acetone

Engineered bacteria could be a boon for sustainable acetone

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Researchers from Hiroshima University have engineered a bacterium to produce acetone at high temperatures, allowing the acetone to be evaporated and distilled as the bacteria feed.

Acetone is a volatile, very corrosive solvent used for everything from removing nail polish and cleaning textiles to manufacturing plastics. It is typically produced through the cost-effective but unsustainable cumene method. This method, which was developed in 1942, involves converting two non-renewable resources into acetone and phenol - another chemical useful in plastics manufacturing.

While there are environmentally friendly alternatives to the cumene method, such as gas fermentation, these tend to be cumbersome and expensive. According to Professor Yutaka Nakashimada of Hiroshima University, one of the major expenses involved is downstream processing, which involves separating the desired chemicals.

“We thought the key is a simultaneous separation of the product from the ongoing fermentation,” said Nakashimada. “Our choice was to produce volatile chemicals by using a group of bacteria thriving at high temperatures.”

The researchers genetically engineered bacteria with modified metabolism processes. The bacteria, Moorella thermoacetica, eat the gaseous feedstocks of hydrogen, carbon dioxide, and monoxide (which can be produced from renewable resources) and produce acetone. This heat-loving bacterium grows at a temperature higher than the boiling point of acetone, meaning that the acetone it produces is a gas which can be distilled as it is produced, streamlining the process.

“Our development of the engineered bacteria could pave the way for developing a consolidated process with simplified and cost-effective recovery via condensation following gas fermentation on a large-scale suitable for industrial production,” said Professor Junya Kato, co-first author of the AMB Express study.

“To our knowledge, this is the first study to provide strains of bacteria that thrive at high temperatures for gas fermentation of acetone. Although further study would be needed to improve the productivity for realisation of the industrialised applications, the gas fermentation process can be simpler and more cost-effective than before.”

Nakashimada, Kato, and their colleagues plan to scale up their work on acetone production and study the productivity of their engineered bacteria under industrial conditions.

“We may need to genetically engineer the metabolism of the strain further,” said Nakashimada. “Our ultimate goal is the industrialisation of the gas fermentation of the gas-to-gas process that is simpler and lower cost.”

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