Research In Biosynthesis of Renewable Propane Moves Step Closer

Researchers at the University of Manchester and Imperial College in England have edited the genome of an algae enzyme and produced propane. e researchers are reported to have made signi cant advances in the search to develop a way of making renewable propane through bioengineering, a promising economic prospect that is also good for the environment.

The team, led by Nigel Scrutton, director of the Manchester Institute of Biotechnology, and Patrik Jones from Imperial College London, have developed a new metabolic pathway for the biosynthesis of propane by genetically engineering an enzyme found in algae. In nature, enzymes are proteins that act as catalysts and help complex reactions occur, such as digestion and photosyn- thesis, often breaking down large molecules into smaller ones.

There is no natural way to make small-chain hydrocarbon propane, so the team first had to identify an enzyme that was capable of working with large hydrocarbon molecules, and then edit its genome. They used an enzyme found in algal cyanobacteria that researchers previously employed to catalyze a reaction in order to form butanol. It was then genetically engineered to make it capable of carrying out a reaction to convert a natural cell substrate into propane, instead of butanol. In other words, an enzyme that was not naturally equipped to change hydrocarbon chains into propane was genetically modi ed to do so. The team’s method was published in the journal Biotechnology of Biofuels.
“We take a natural enzyme, we reengineer it to do a different type of chemistry with a different small molecule specifically,” Scrutton explains. “Having done that, we can use that in something we call metabolic engineering to make an artificial pathway that then converts that into propane gas.” Propane traditionally is sourced from conventional natural gas and oil reserves, so in its traditional form it isn’t renewable. The team’s new biosynthesis pathway uses biomass or waste feedstocks, which could come from plants or waste streams from other industrial processes.

“If you’re depleting a feedstock to feed these bacteria, you can replenish that feedstock through natural photosynthesis,” says Scrutton. “If it’s a plant-based feed-stock you harvest that, you feed the bacteria on it, you re-grow your crop and fix carbon dioxide for the atmosphere as part of the photosynthetic process. It’s more of a closed loop.” The team was challenged when trying to determine how to reengineer the enzyme. “We have ways of studying [enzyme] structures, but it’s just by looking at the structure. You can’t then easily understand how to change the structure to give it a diferent function,” Scrutton adds. “This is something that biochemists have been trying to do, and structural biology has been trying to do for many, many years. It’s a bit of a black art.”