SIOUX FALLS — A South Dakota State University researcher is looking into ways to reuse enzymes, a high-cost ingredient in the making of ethanol from such nonfood feedstocks as switch grass, bluestem and corn stover.
Enzymes are proteins that serve as catalysts in many natural and manmade processes, including the conversion of plants’ cellulose into biofuels.
But the expensive enzymes typically float away after they do their job, said Basil Dalaly, a professor in SDSU’s Nutrition, Food Science and Hospitality Department.
Dalaly and graduate student Pavani Mandali are experimenting with ways to reuse the enzymes by chemically attaching them to glass beads, then using the beads multiple times. It’s an approach used in the food industry to produce such substances as high-fructose corn syrup.
Enzymes can account for as much as $1 per gallon of the costs of producing cellulosic ethanol, which are running some companies around $2 per gallon. Dalaly is hoping to cut that cost in half.
“Instead of using the enzyme once and throwing it away, we’re immobilizing the enzymes on beads and using the enzymes for three, four or five cycles,” he said. “In doing so, we’re reducing the cost of enzymes.”
Mark Stowers, senior vice president of science and technology at ethanol producer Poet, said enzymes are one of the highest costs in cellulosic ethanol production. Enzyme producers are reducing costs, but new avenues should be explored, he said.
“The work at SDSU has the potential to shake up the current paradigm of enzyme technology, and we will be watching closely with the hope that their work reaches commercial fruition,” Stowers said.
Dalaly’s research, which began five years ago, is funded by the U.S. Energy, Transportation and Agriculture departments. Danish company Novozymes is providing the enzymes.
SDSU scientists are producing the ethanol from switch grass, bluestem, corn stover and distillers grains, with engineers in the university’s Agricultural and Biosystems Engineering Department pretreating the biomass.
Once the enzymes are chemically attached to the beads, they’re used to grab the cellulose out of the feedstocks.
Researchers then collect the enzyme-covered beads and add them to a new batch, though reuse has a point of diminishing returns.
The enzymes lose about 10 percent of their activity after the first cycle, and their effectiveness is cut in half by the fourth or fifth cycle.
Dalaly said researchers are trying to figure out how to preserve as much activity in the beads, and they also need to quantify how attaching the enzymes to the beads changes their properties.
“We have a lot of work ahead of us,” he said.
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