It sounds like modern-day alchemy: Transforming sugar into hydrocarbons
found in gasoline.
But that's exactly what scientists have done.
In a forthcoming study in Nature Chemistry, researchers report harnessing
the wonders of biology and chemistry to turn glucose (a type of sugar) into
olefins (a type of hydrocarbon, and one of several types of molecules that
make up gasoline).
The project was led by biochemists Zhen Q. Wang at the University at Buffalo
and Michelle C. Y. Chang at the University of California, Berkeley.
The paper, which will be published on Nov. 22, marks an advance in efforts
to create sustainable biofuels.
Olefins comprise a small percentage of the molecules in gasoline as it's
currently produced, but the process the team developed could likely be
adjusted in the future to generate other types of hydrocarbons as well,
including some of the other components of gasoline, Wang says. She also
notes that olefins have non-fuel applications, as they are used in
industrial lubricants and as precursors for making plastics.
A two-step process using sugar-eating microbes and a catalyst
To complete the study, the researchers began by feeding glucose to strains
of E. coli that don't pose a danger to human health.
"These microbes are sugar junkies, even worse than our kids," Wang jokes.
The E. coli in the experiments were genetically engineered to produce a
suite of four enzymes that convert glucose into compounds called 3-hydroxy
fatty acids. As the bacteria consumed the glucose, they also started to make
the fatty acids.
To complete the transformation, the team used a catalyst called niobium
pentoxide (Nb2O5) to chop off unwanted parts of the fatty acids in a
chemical process, generating the final product: the olefins.
The scientists identified the enzymes and catalyst through trial and error,
testing different molecules with properties that lent themselves to the
tasks at hand.
"We combined what biology can do the best with what chemistry can do the
best, and we put them together to create this two-step process," says Wang,
PhD, an assistant professor of biological sciences in the UB College of Arts
and Sciences. "Using this method, we were able to make olefins directly from
glucose."
Glucose comes from photosynthesis, which pulls CO2 out of the air
"Making biofuels from renewable resources like glucose has great potential
to advance green energy technology," Wang says.
"Glucose is produced by plants through photosynthesis, which turns carbon
dioxide (CO2) and water into oxygen and sugar. So the carbon in the glucose
-- and later the olefins -- is actually from carbon dioxide that has been
pulled out of the atmosphere," Wang explains.
More research is needed, however, to understand the benefits of the new
method and whether it can be scaled up efficiently for making biofuels or
for other purposes. One of the first questions that will need to be answered
is how much energy the process of producing the olefins consumes; if the
energy cost is too high, the technology would need to be optimized to be
practical on an industrial scale.
Scientists are also interested in increasing the yield. Currently, it takes
100 glucose molecules to produce about 8 olefin molecules, Wang says. She
would like to improve that ratio, with a focus on coaxing the E. coli to
produce more of the 3-hydroxy fatty acids for every gram of glucose
consumed.
Reference:
Zhen Q. Wang, Heng Song, Edward J. Koleski, Noritaka Hara, Dae Sung Park,
Gaurav Kumar, Yejin Min, Paul J. Dauenhauer, Michelle C. Y. Chang. A dual
cellular-heterogeneous catalyst strategy for the production of olefins from
glucose. Nature Chemistry, 2021;
DOI: 10.1038/s41557-021-00820-0
Tags:
Chemistry