Researchers at the US Department of Energy’s (DOE’s) National Renewable Energy Laboratory (NREL) and the University of Georgia have developed a new genetic engineering technique significantly to improve an enzyme’s ability to break down biomass. A paper on the work is published in Proceedings of the National Academy of Sciences (PNAS).

The new method, Evolution by Amplification and Synthetic Biology (EASy), enabled scientists to accelerate the evolution of a microorganism’s desirable traits. This 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.

The EASy method enables the back-to-back incorporation of hundreds of copies of a gene—which contains the code for a specific enzyme—into a cell. This region of repetitive DNA provides the cell with a means to undergo accelerated evolution of this gene. This can ultimately lead to the generation of superior performing enzymes.

We can make many, many random changes and identify those that are of interest using evolution.

—Christopher Johnson, a molecular biologist in NREL’s National Bioenergy Center and co-author

Researchers inserted DNA that encodes the enzyme GcoA from the bacteria Amycolatopsis into another bacteria, 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% of biomass.

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

—Jeffrey Linger, co-author

Funding for the research came from DOE’s Bioenergy Technologies Office.

Resources

• Melissa Tumen-Velasquez, Christopher W. Johnson, Alaa Ahmed, Graham Dominick, Emily M. Fulk, Payal Khanna, Sarah A. Lee, Alicia L. Schmidt, Jeffrey G. Linger, Mark A. Eiteman, Gregg T. Beckham, Ellen L. Neidle (2018) “Accelerating pathway evolution by increasing the gene dosage of chromosomal segments” Proceedings of the National Academy of Sciences doi: 10.1073/pnas.1803745115