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Two doctoral students receive Nelson graduate scholarships

butanol separation
Activated carbon made from cornstalks has a a higher butanol absorption capacity than commercial carbon, according to doctoral student Yuhe Cao.

Two doctoral candidates from the College of Agriculture and Biological Sciences have been named recipients of the Joseph F. Nelson Graduate Scholarship Award. This is the first time that the scholarship, which recognizes original scientific research, has been shared by two graduate students. Each will receive $2,500 for tuition and expenses.

Yuhe Cao of the Department of Agricultural and Biosystems Engineering is improving separation methods for biofuels and Suresh Damodaran of the Department of Agronomy, Horticulture and Plant Science seeks to increase the nitrogen-fixing ability of soybeans. Both will complete their doctorates this year.

Developing separation methods

Cao developed a method to separate a compound called glucosinolate from camelina, a broadleaf oilseed from the mustard family. Glucosinolate is one of the bioactive compounds that remains after the oil has been extracted, according to Cao’s adviser, associate professor Zhengrong Gu. Camelina oil is used as feedstock to produce jet fuel. The presence of glucosinolate limits the amount of camelina meal that can be incorporated into animal diets to 10 percent.

Zhengrong Gu and Yuhe Cao
Zhengrong Gu and Yuhe Cao, right, use a chemisorption analyzer to recover butanol.

 “It’s very toxic,” he pointed out, and it’s that toxicity that Gu wants to utilize—to kill fungus, weeds or even cancer cells. He hopes that developing high-value uses for glucosinolate will help make biofuel production profitable, without government subsidies.

Cao extracts the glucosinolate with ethanol and then uses membrane filtration to remove impurities, such as proteins. Then he uses an ion exchange column to further purify the glucosinolate.

In addition, Cao developed a more efficient means of separating butanol from the fermented lignocellulosic biomass. Butanol has a higher energy content than ethanol and can be used in conventional gas engines without modifications, according to

Cao’s process continuously absorbs the butanol while preserving the fermentation microorganisms and capturing butanol in higher concentrations with less energy consumption than the traditional distillation methods. The research team has filed an invention closure on the new separation method.

The research is supported by the U.S. Department of Energy through the Sun Grant Initiative, which supports the development of renewable, biobased energy technologies, and the South Dakota Oilseeds Initiative.

Unraveling soybean genetics

The soybean plant, a legume, interacts with bacteria in the soil to form organs called nodules, explained Damodaran. His research focuses on understanding how a hormone called auxin affects soybean nodule development and identifying which genes are involved in its production.

His work is part of a National Science Foundation project to identify the genetic mechanisms that direct and coordinate formation of the soybean nodule. Damodaran’s adviser, associate professor Senthil Subramanian, hopes to increase the plant’s ability to fix nitrogen and thus reduce the need for chemical fertilizers.

Suresh Damodaran
Suresh Damodaran examines soybean seedlings that will help determine which genes affect nodule development.

The research group had already discovered that auxin reduces nodule numbers. Consequently, Damodaran worked with colleagues on a large-scale experiment to see which genes are expressed in the nodule tissue. His research focused on the SUR2 gene.

“If we consider genes as workers involved in construction of the nodules, to determine one particular gene’s function we take that gene or worker out of the system and see how the construction goes,” Damodaran explained. Reducing the expression of the SUR2 gene and thus increasing auxin production decreased the number of nodules the soybean plant formed.

Conversely, when Damodaran treated the plant with a chemical that reduces auxin levels, the nodule numbers increased. In addition to supporting the initial evidence regarding auxin’s role in nodule development, Damodaran is the first to report the key role that the SUR2 gene plays in this process.

“This guy is really important,” he said, noting that it is unusual to identify this type of impact from a single gene. In most cases, multiple genes are involved.

 But, Damodaran cautioned, this is just one piece of the bigger model that will ultimately help the researchers optimize overall nodule development.