To make biofuel from inorganic, gaseous industrial waste, the researchers learned that the bacterium Clostridium ljungdahlii responds thermodynamically - rather than genetically - in the process of tuning favourable enzymatic reactions.

"Instead of having the waste go to waste, you make it into something you want. In order to make the microbes do our work, we had to figure out how they work, their metabolism," said Ludmilla Aristilde, assistant professor at Cornell University in the US.

Synthetic gas - or syngas - fermentation is emerging as a key biotechnological solution, as industrial-sized operations are looking to produce ethanol from their gaseous waste streams, according to Lars Angenent, professor at Cornell.

The scientists sought to grasp the physiological nature of the process.

"These findings are important for the syngas fermentation community to design future strategies to improve production," Angenent said.

The scientists found the microbe feasts on and then ferment carbon monoxide.

"The bacterial cells are starving for nutrients, so they are responding metabolically - which leads to a desired outcome, ethanol production," Aristilde said.

To get the microbe to ferment the carbon monoxide, scientists "bubble it in the growth medium solution," said Angenent, where the cells can feed on it.

Angenent said carbon monoxide gas emitted as a byproduct of heavy industries - such as the process for coking coal in the production of steel - can potentially be channelled to bioreactors that contain these bacterial cells.

"The microbial cells then turn it into ethanol, an organic molecule. And carbon monoxide, an inorganic molecule, turns into something valuable we can use," said Aristilde.

The study was published in the journal Energy and Environmental Science.

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