New artificial enzyme breaks down tough, woody lignin

A new artificial enzyme has shown it can chew through lignin, the tough polymer that helps woody plants hold their shape. Lignin also stores tremendous potential for renewable energy and materials.

In nature, fungi and bacteria are able to break down lignin with their enzymes, which is how a mushroom-covered log decomposes in the forest. Enzymes offer a much more environmentally benign process than chemical degradation, which requires high heat and consumes more energy than it produces. But, natural enzymes degrade over time, which makes them hard to use in an industrial process. They're expensive, too.

The researchers replaced the peptides that surround the active site of natural enzymes with protein-like molecules called peptoids. These peptoids then self-assembled into nanoscale crystalline tubes and sheets. Peptoids were first developed in the 1990s to mimic the function of proteins. They have several unique features, including high stability, that allow scientists to address the deficiencies of the natural enzymes.

Reporting in the journal Nature Communications, a team of researchers from Washington State University and the Department of Energy's Pacific Northwest National Laboratory showed that their artificial enzyme succeeded in digesting lignin, which has stubbornly resisted previous attempts to develop it into an economically useful energy source. As expected, these artificial enzymes are also much more stable and robust than the natural versions, so that they can work at temperatures up to 60 degrees Celsius, a temperature that would destroy a natural enzyme.