UGA, NREL researchers create novel genetic method

Researchers from the University of Georgia, in conjunction with researchers at the Department of Energy’s National Renewable Energy Laboratory (NREL), have developed a new genetic engineering technique that dramatically improves an enzyme’s ability to break down biomass.

Ellen Neidle, professor of microbiology at UGA, and her lab team helped create the novel method known as Evolution by Amplification and Synthetic Biology (EASy) that enables scientists to accelerate the evolution of a microorganism’s desirable traits.

The technique led to the unusual fusion of enzymes from two different species of bacteria and contributed to the emerging use of microbes to convert lignin, a major component of plant biomass, into valuable chemicals.

“This novel method was developed by our team, led by UGA postdoctoral researcher Melissa Tumen-Velasquez,” said Neidle. “She inserted foreign genes, provided by collaborators at NREL, into the chromosome of a bacterium that has a malleable genetic system, Acinetobacter baylyi. By exploiting genetic tools devised at UGA for this bacterium, segments of the chromosome carrying the foreign DNA were specifically duplicated such that multiple gene copies were available to undergo evolution concurrently. This process accelerates the selection of desirable traits in the laboratory by recapitulating a natural process that would otherwise occur randomly and slowly.”

While this study shows that the method is successful in converting lignin-derived aromatic compounds, this evolutionary method could also be used for generating many types of enzymes and pathways that could be used for biotechnology.

“Researchers at NREL demonstrated the broader utility of the method by showing that the resulting enzymes could be effectively used in a different bacterium that serves as a model for converting lignin-derived aromatic compounds into useful chemicals,” she said.

Published in the journal Proceedings of the National Academy of Sciences of the United States of America, the paper also was co-authored by Melissa Tumen-Velasquez, Alaa Ahmed, Sarah Lee, Alicia Schmidt, Mark Eiteman, and Ellen Neidle from the University of Georgia; and Graham Dominick, Emily Fulk, Paval Khanna, Jeffrey Linger, and Gregg Beckham, from NREL. Funding for the research came from the National Science Foundation and the Bioenergy Technologies Office at the U.S. Department of Energy. 

Researchers inserted DNA that encodes the enzyme GcoA from the bacterium Amycolatopsis into another bacterium, Acinetobacter baylyi ADP1, placing it adjacent to the gene that encodes the CatA enzyme. The EASy technique resulted in the unusual fusion of two genes into a single gene encoding a chimeric enzyme.

The trait afforded by this chimeric enzyme was the ability to more efficiently convert a component of lignin—a particularly resilient part of plant biomass—into fuels and a precursor of plastics such as nylon Lignin comprises about 30 percent of biomass.

“It’s a matter of conversion efficiency,” said Linger. “If you’re not using that 30 percent, you’re throwing it away. We’re trying to capture that 30 percent.”

Want to know more about this research? Read the paper here: http://www.pnas.org/content/early/2018/06/13/1803745115