Genetically engineered enzyme better at breaking down biomass

Scientists at the US Department of Energy’s (DOE) National Renewable Energy Laboratory (NREL) and the University of Georgia have developed a new genetic engineering technique to dramatically improve an enzyme’s ability to break down biomass, with the results described in the journal Proceedings of the National Academy of Sciences.

The method, known as ‘Evolution by Amplification and Synthetic Biology (EASy)’, enabled the 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,” said study co-author Christopher Johnson, a molecular biologist in NREL’s National Bioenergy Center.

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 fuel, and a precursor of plastics such as nylon lignin which comprise about 30% biomass.

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

Image caption: Gregg Beckham, Christopher Johnson and Jeffery Linger are co-authors of a new researcher paper that details how they improved the efficiency of an enzyme in breaking down biomass. Image credit: Dennis Schroeder/NREL.