A research team at Michigan State University has published the results of its study into producing squalene from poplar trees for use in biofuel production.
An oil compound found in shark livers, squalene is used in cosmetic products and vaccines.
Published in the Plant Biotechnology Journal, the team’s paper ‘Engineered poplar for bioproduction of the triterpene squalene’ reports new findings that could help engineer poplar trees to produce the chemical.
Producing the compound could increase the economic viability of poplar trees as a biofuel feedstock, the study team led by Björn Hamberger said on the University website on 8 July.
“I think this project really highlights how we can use industrial crops in new ways,” Jake Bibik, first author on the paper said.
“Using engineered, non-food crops like poplar may provide a more sustainable alternative for generating chemicals typically derived from fossil fuels, or even new speciality chemicals altogether.”
Although poplars have attributes that make them suitable for use as a biofuel feedstock due to their growth rates and dense biomass, the biggest challenge is economics, according to the research team.
“Biofuels are still not competitive against the … petrochemistry that’s out there,” study lead Hamberger, who is also a co-investigator at the Great Lakes Bioenergy Research Center (GLBRC), led by the University of Wisconsin–Madison and funded by the US Department of Energy said.
As part of the project, the team engineered poplars to produce squalene along two distinct chemical pathways.
One pathway used the gel-like substance known as cytosol found in the centre of cells, while another focused on producing squalene in chloroplasts, the organelles responsible for photosynthesis.
While the cytosol pathway was discovered to interfere with poplar root formation, the chloroplast route produced 0.63 mg/gm of squalene in leaves.
The team’s next step – working with Christos Maravelias, a professor of chemical and biological engineering at Princeton University – was to calculate the minimum sales price the poplar-produced squalene would need to be sold at to be commercially successful.
Shark-derived squalene is marketed at US$40/kg while the price for the poplar-produced compound was calculated at US$40/kg.
However, Hamberger said several options were available to boost the value of poplar-produced squalene.
“One way is increasing overall production, and the other brings us to the … world of perfumes and another marine animal product – ambergris,” he said.
Produced in the digestive system of sperm whales, ambergris is used as a fixative in perfumes to prolong scents.
Hamberger said it should be possible to “upgrade” squalene to ambrein, another high-value terpene that makes up ambergris.
