New techniques would convert biofuels waste into high-value chemicals

Washington, July 1 : Chemical engineers at Rice University have unveiled a set of techniques for cleanly converting problematic biofuels waste into chemicals that fetch a profit.

The techniques include 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," he added.

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 2010.

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 that 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," said Gonzalez. "This knowledge base is enabling our efforts to develop new technologies for converting glycerol into high-value chemicals," he added.

According to Gonzalez, 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 previously unknown metabolic pathway for glycerol fermentation, a pathway that uses 1,2-PDO, a chemical similar to 1,3-PDO, that E. coli can produce.

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.

"We want to use the technology as a platform for the 'green' production of a whole range of high-value products," said Gonzalez.

ANI