New enzyme speeds up sugar to biofuel system without using yeast

Australian researchers have found a way to more effectively convert sugarcane into the building block of aviation fuel, and other products like rubber and plastics.

Sugarcane (and its waste product) is one of the crops that has shown promise in being turned into ‘biofuel’, which could one day lower aviation’s reliance on fossil fuels.

“The use of renewable lignocellulosic biomass in refineries to produce bulk and high-value chemicals  has recently gained increasing traction and represents an alternative approach to replacing fossil fuels,” the researchers from University of Queensland (UQ) write in their new paper.

“However, the development of a sustainable and cost-effective bioprocesses to out-compete fossil fuel usage is challenging.”

The team – based at UQ and the Technical University of Munich – was able to create an enzyme called PuDHT that sped up the step from turning sugar into pyruvate and then into a useful feedstock chemical called isobutanol.

Isobutanol is a bit like the self-raising flour for chemists. It’s an ‘ingredient’ that can be used in a variety of ways to make anything from fuels, plastics, rubbers and food additives.

The team also tested using manganese and magnesium ions to speed up the process even more.

“Our research into this particular enzyme means we can accelerate the production rate and yield of isobutanol from sugarcane,” said UQ biochemist Professor Gary Schenk.

“Usually during a biomanufacturing process, cells such as yeasts are used as a production platform, but in our research only a small number of a sugar acid-specific dehydratase enzyme was used.”

“Having sugar-converting enzymes operate outside a cellular environment meant we could bypass many of the pitfalls of the more traditional cell-based biomanufacturing methods,” says Schenk.

“This has led to much higher yields of isobutanol with fewer unwanted side products.”

Cell-based production of isobutanol from sugar creates about 25 grams per litre of liquid cell culture, but, the ‘cell-free’ method in the new study produced at least 10 times that amount.

If researchers can secure enough enzymes at a cost that is economically viable, this method could be used in ‘bulk’ products like aviation biofuel.

“While there have been commercial limitations to producing the enzymes, we now have enough evidence to show that large-scale manufacturing using the cell-free enzymes process is commercially viable and should play a major role in future biomanufacturing,” said Professor Damian Hine, also from UQ. The research has been published in Chemistry – a European Journal.