Research yields pricey chemicals from biodi...(iate glycerol fermentation in E. coli ...)

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 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.

"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 run-of-the-mill 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 lactate.

"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-
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