The Byproducts of Biodiesel Production Are Valuable Organic Acids,
by Jade Boyd, Rice News Staff
Houston, United States [RenewableEnergyWorld.com]
In a move that could possibly change the economics of biodiesel
refining, chemical engineers at Rice University have come up with
a set of techniques for converting sometimes problematic biofuels
waste into chemicals that fetch a profit.
The latest research, which was funded by the U.S. Department of
Agriculture, the National Science Foundation, Rice University and
Glycos Biotechnologies, involves a new fermentation process that
allows E. coli and other enteric bacteria to convert glycerin ???
the major waste byproduct of biodiesel production ??? into
formate, succinate and other valuable organic acids.
"Biodiesel producers used to sell their leftover glycerin, but the
rapid increase in biodiesel production has left them paying to get
rid of it," said lead researcher Ramon Gonzalez, Rice's William W.
Akers Assistant Professor in Chemical and Biomolecular
Engineering. "The new metabolic pathways we have uncovered paved
the way for the development of new technologies for converting
this waste product into high-value chemicals."
About one pound of glycerin, also known as glycerol, is created
for every 10 pounds of biodiesel produced. According to the
National Biodiesel Board, U.S. companies produced about 450
million gallons of biodiesel in 2007, and about 60 new plants with
a production capacity of 1.2 billion gallons are slated to open by
Gonzalez's team last year announced a new method of glycerol
fermentation that used E. coli to produce ethanol, another
biofuel. Even though the process was very efficient, with
operational costs estimated to be about 40 percent less that those
of producing ethanol from corn, Gonzalez said new fermentation
technologies that produce high-value chemicals like succinate and
formate hold even more promise for biodiesel refiners because
those chemicals are more profitable than ethanol.
"With fundamental research, we have identified the pathways and
mechanisms that mediate glycerol fermentation in E. coli,"
Gonzalez said. "This knowledge base is enabling our efforts to
develop new technologies for converting glycerol into high-value
Gonzalez said scientists previously believed that the only
organisms that could ferment glycerol were those capable of
producing a chemical called 1,3-propanediol, also known as
1,3-PDO. Unfortunately, neither the bacterium E. coli nor the
yeast Saccharomyces ??? the two workhorse organisms of
biotechnology ??? were able to produce 1,3-PDO.
Gonzalez's research revealed a metabolic pathway for glycerol
fermentation, one that uses 1,2-PDO, a chemical similar to
1,3-PDO, that E. coli can produce.
"The reason this probably hadn't been discovered before is that E.
coli requires a particular set of fermentation conditions for this
pathway to be activated," Gonzalez said. "It wasn't easy to zero
in on these conditions, so it wasn't the sort of process that
someone would stumble upon by accident."
Once the new metabolic pathways were identified, Gonzalez's team
began using metabolic engineering to design new versions of E.
coli that could produce a range of high-value products. For
example, while basic E. coli ferments glycerol to produce very
little succinate, Gonzalez's team has created a new version of the
bacterium that produces up to 100 times more. Succinate is a
high-demand chemical feedstock that's used to make everything from
noncorrosive airport deicers and nontoxic solvents to plastics,
drugs and food additives. Most succinate today comes from
nonrenewable fossil fuels.
Gonzalez said he's had similar success with organisms designed to
produce other high-value chemicals, including formate and
"Our goal goes beyond using this for a single process," he said.
"We want to use the technology as a platform for the 'green'
production of a whole range of high-value products."
Technologies based on Gonzalez's work have been licensed to Glycos
Biotechnologies Inc., a Houston-based startup company that plans
to open its first demonstration facility within the next 12
Kyle J. Fricker
University of Florida