The Byproducts of Biodiesel Production Are Valuable Organic Acids, 
Researchers Say
by Jade Boyd, Rice News Staff
Houston, United States []

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
Chemical Engineering
University of Florida