Researchers in Britain say they've made a significant advance in the search for a process to enable renewable production of the gas propane, previously only produced in quantity from fossil fuels.

Natural metabolic pathways for biosynthesis of propane do not exist, but scientists from the University of Manchester and Imperial College London report that they've come up with an alternative microbial biosynthetic pathway that will allow renewable production.

Commercial production capability of renewable propane is seen as a high priority as fossil fuel supplies are steadily consumed and continue to dwindle, they note.

"The chemical industry is undergoing a major transformation as a consequence of unstable energy costs, limited natural resources and climate change," says Nigel Scrutton, head of the project. "Efforts to find cleaner, more sustainable forms of energy as well as using biotechnology techniques to produce synthetic chemicals are currently being developed at the University of Manchester."

The researchers utilized a genetically engineered enzyme introduced into an existing fermentation pathway that produces butanol to redirect that microbial path to instead produce propane, they report in the journal Biotechnology of Biofuels.

Propane can be stored and transported in a liquid form under pressure, then as ambient temperature becomes a gas that burns cleanly, which, in cars produces greenhouse gas emissions up to 20 percent lower than unleaded gasoline.

Existing worldwide markets and in-place infrastructure for distribution, storage and use make propane an attractive target for researchers into new renewable options to current fuels derived from petroleum, the scientists say.

Currently, the usual sources for production of propane are during gasoline refining and natural gas processing.

"This study focused on the construction and evaluation of alternative microbial biosynthetic pathways for the production of renewable propane," Scrutton says. "It also expands the metabolic toolbox for renewable propane production, providing new insight and understanding of the development of next-generation biofuels which one day could lead to commercial production."

There have been previous efforts to create renewable propane; last year, another research team at Imperial College London made propane from glucose utilizing a genetically engineered version of E. coli bacteria.

However, as a proof of concept experiment, it produces only tiny amounts of propane and would require scaling up the process considerably for it to be commercially viable, the researchers said.

Still, it is one more small step in the right direction, said Patrik Jones, lead author of a study published in Nature Communications.

"We can now make a product that until now was only available from fossil fuels and it's chemically identical," he said at the time. "It should work exactly the same as normal propane."

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