Microbial Tricks for the Glycerol Trade

APSU researchers discover useful byproducts from glycerin
By Bryan Sims | March 09, 2011

As biodiesel supply and demand grow, a steady stream of glycerin is expected to follow, and research is underway to find new use methods for the biodiesel byproduct. Researchers at Austin Peay State University in Clarksville, Tenn., have discovered a novel method for converting glycerol into value-added coproducts such as hydrogen and ethanol.

With funding from the National Science Foundation and the U.S. EPA, Sergi Markov, associate professor of biology, and two of his students, Jared Averitt and Barbara Waldron, have studied the effects of the bacterium Enterobacter aerogenes on glycerol. The team concluded that when Enterobacter bacterium feeds on crude glycerol under anaerobic conditions in a traditional stirred-tank bioreactor, a significant amount of hydrogen and ethanol is produced, including trace quantities of lactate, acetate, 1,3-propanediol and formate.

Markov, Averitt and Waldron co-authored a paper on their findings, titled “Bioreactor for Glycerol Conversion into H2 by Bacterium Enterobacter aerogenes,” which was published earlier this year in the International Journal of Hydrogen Energy.

Specifically, Markov tells Biodiesel Magazine that he obtained approximately 22 liters of hydrogen from a 17 liter-volume bioreactor per hour and 50 milliliters of hydrogen from a 35 milliliter-volume bioreactor per hour. From there, Markov explains, enough hydrogen was produced that he could inject it from the bioreactor directly into a small fuel cell to power a small fan in the lab.

 “Our process for conversion of glycerol into hydrogen fuel is possible to scale up pretty quickly,” Markov says. “We can also use hydrogen as an energy source or as an energy carrier.”

According to Markov, the research on glycerol utilization stems from work he and his team initially did while trying to find efficient ways to produce biodiesel from cultivated algae oil. Since glycerol was an end coproduct in their trial runs, Markov says that’s when the decision was made to study new uses for the compound.

“We were actually more successful converting glycerol into hydrogen than we were converting biodiesel from the algae oil,” Markov says. “Biodiesel from algae oil is still a work in progress for us.”

—Bryan Sims

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