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Microreactor efficiently regenerates cofactors for biocatalysis


James E. Kloeppel, Physical Sciences Editor
217-244-1073; kloeppel@illinois.edu

7/19/2005

Paul Kenis working in his lab
Click photo to enlarge
Photo by Kwame Ross
Paul Kenis and colleagues at the Université Paul Sabatier in Toulouse, France, has developed a microreactor that efficiently regenerates cofactors through enzyme-catalyzed reactions.

CHAMPAIGN, Ill. –– One of the longstanding challenges in the synthesis of pharmaceuticals, cosmetics and food additives is the continuous regeneration of molecules called cofactors that permit the synthesis through inexpensive and environmentally friendly biocatalytic processes.

Now, a team of researchers from the University of Illinois at Urbana-Champaign and the Université Paul Sabatier in Toulouse, France, has developed a microreactor that efficiently regenerates cofactors through enzyme-catalyzed reactions.

 

conceptual graphic showing the focusing of a stream of reactants closely to a cathode
Click photo to enlarge
Courtesy Paul Kenis
Focusing of a stream of reactants closely to the cathode in a microfluidic reactor enables efficient regeneration of the cofactor NADH. This in turn allows for the biocatalytic conversion of achiral substrates (e.g. pyruvate) into chiral products (e.g. L-lactate) that are important in the synthesis of pharmaceuticals, cosmetics, insecticides, and food additives.

“Enzymes are nature’s catalysts, but in some cases, enzymes can not prompt a speedy chemical reaction,” said Paul Kenis, a professor of chemical and biomolecular engineering at Illinois and a researcher at the Beckman Institute for Advanced Science and Technology. “In those cases, one or more cofactors are required.”

By continuously regenerating the required cofactors, the microreactor enables the desired biocatalytic processes. Kenis and his colleagues describe their work in a paper that has been accepted for publication in the Journal of the American Chemical Society, and posted on its Web site.

The microreactor uses a Y-shaped microfluidic channel in which two liquid streams (a reactant stream and a buffer stream) merge and flow laminarly between two electrodes without mixing. By adjusting the flow rates of the two streams, the researchers can focus the reactant stream close to the cathode, and a normally unfavorable reaction equilibrium is driven into the desired direction of cofactor regeneration.

“In large batch reactors, a spontaneous reverse reaction prevents the regeneration of essential cofactors,” Kenis said. “The absence of a bulk phase in our microreactor prevents the unwanted reverse reaction from occurring, while permitting continuous operation.”

Using their microreactor, the researchers performed a model biocatalytic process by converting an achiral substrate (pyruvate) into a chiral product (L-lactate), using lactate dehydrogenase as the enzyme.

While further research is needed to improve the performance of individual microreactors, the present work shifts the emphasis from the longstanding problem of cofactor regeneration to a more tangible engineering challenge, Kenis said. “Now we need to integrate a large number of these microreactors in a recirculating system to enable the biocatalytic synthesis of chiral fine chemicals in larger quantities.”

Collaborators included electrochemical engineering professor Theodore Tzedakis and graduate student Cheikhou Kane at the Université Paul Sabatier and graduate students Eric Choban and Seong Kee Yoon at Illinois. Funding was provided by the University of Illinois and the National Center for Scientific Research in France (CNRS), as well as a formal exchange program between these two institutions.

Editor’s note: To reach Paul Kenis, call 217-265-0523; e-mail: kenis@illinois.edu.