New technology could fuel biorefinery growth

ARGONNE, Ill. (June 28, 2005) – Researchers at the U.S. Department of Energy's Argonne National Laboratory and Archer Daniels Midland Co. (ADM) are developing a separative bioreactor that efficiently turns sugar from corn into valuable chemicals. The technology could help bio-based chemicals replace large amounts of petrochemicals, thereby reducing U.S. dependence on foreign oil, benefiting rural economies and reducing greenhouse gas emissions.

The two-year joint research effort will evaluate and optimize the production of gluconic acid using the separative bioreactor. Eventually, the technology could extend beyond gluconic acid to the production of a variety of organic acids and polyols, which form the chemical building blocks for plastics, pharmaceuticals and other consumer products.

Gluconic acid is produced by the biochemical oxidation of glucose, a sugar found in corn starch. This reaction, facilitated by enzymes in fermentation broths, has been known for more than 100 years, said YuPo Lin, a chemical engineer in Argonne 's Energy Systems Division. He said the challenge is one of engineering – how to process gluconic acid cheaply and cleanly enough to compete economically with petrochemicals.

The separative bioreactor, developed by a multidisciplinary team of ES scientists, could overcome technical and economic barriers to the production of gluconic acid, said Seth Snyder, the principal investigator at Argonne .

Argonne researchers have learned how to immobilize the enzyme that turns glucose into gluconic acid, and they have merged that capability with a separation process called electrodeionization (EDI). EDI uses electricity to remove even low concentrations of ions from a solution; it is commonly used in biochemical labs, chemical and semiconductor factories to produce ultrapure water. ES researchers developed and patented an improved EDI resin wafer stack that won a 2002 R&D 100 Award. Funding for the stack research, which efficiently removes salt, added during a manufacturing process, from high fructose corn syrup, was provided by DOE's Industrial Technology program.

Inside the separative bioreactor, enzymes convert a steady stream of glucose into gluconic acid. The gluconic acid ionizes and is immediately separated from the glucose solution by the EDI process.

The EDI separation eliminates a major problem in large-scale gluconic acid production – the incompatibility of the enzyme and the product acid. As the acid builds up, it deactivates the enzyme and shuts down the fermentation.

Previously, this problem was solved by adding chemicals to neutralize the product acid, much like people use antacids to neutralize stomach acid, but that process generates additional waste. The Argonne separative bioreactor operates continuously using only electricity to separate the product. Snyder said the cost of the electricity is “very, very small. It's well within our goals for the overall bioprocessing cost.”

In the test-scale systems at Argonne , the process has been demonstrated effectively at speeds of about a gallon of glucose solution a day. A commercial-scale reactor would be several times larger, and hundreds of units would be stacked together to achieve industrial-scale output.

ADM, one of the largest producers of gluconic acid in the world, understands the economics of large-scale production, Snyder said, adding that economics – not environmental considerations – will determine the commercial success of any bio-based production process, although bio-based production does offer substantial environmental benefits.

For now, Argonne researchers are testing and improving the separative bioreactor's efficiency at turning glucose into gluconic acid. “We chose gluconic acid because researchers at Argonne are interested in the enzyme glucose-fructose oxidoreductase,” Snyder said. “If we prove the technology with this enzyme, and ADM commercializes it, the other applications will come along nicely, but you need that first commercial success before you worry about the third or fourth,” Snyder said.

Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation's first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America 's scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy's Office of Science.

For more information, please contact Steve McGregor (630/252-5580 or media@anl.gov) at Argonne.