Plastic pollution remains a major environmental challenge because many conventional plastics resist decomposition, gradually breaking into microplastics and nanoplastics instead of disappearing. However, researchers at the University of Konstanz in Germany have discovered an unusual enzyme that helps bacteria break down certain biodegradable plastics.

Published in The ISME Journal, the study identifies an enzyme nicknamed the “Pac-Man enzyme” because of its unusually wide active site, where chemical reactions occur. Researchers Harry Lerner and David Schleheck investigated how microorganisms decompose long-chain aliphatic polyesters (LCAP), a type of biodegradable plastic.

The scientists buried plastic film in forest soil and monitored microbial activity in laboratory experiments over a year. The biodegradable plastics decomposed completely within approximately 250 to 330 days, while conventional high-density polyethylene showed virtually no degradation.

Electron microscopy revealed tiny holes in the recovered plastic films, suggesting that bacteria were breaking into the material rather than simply growing on its surface.

By analyzing microbial DNA, the researchers identified a gene that produces an esterase, an enzyme capable of breaking chemical bonds found in biodegradable polyesters. The enzyme's structure allows it to remain attached to bacterial cells while attacking nearby plastic molecules.

The findings suggest that microorganisms may adapt to digest certain biodegradable materials more readily than previously understood. However, the discovery does not mean bacteria can readily break down conventional plastics, which remain highly resistant to microbial degradation.

The researchers argue that developing plastics with chemical bonds that microorganisms can break apart could help address pollution. By designing materials around microbial capabilities, scientists may eventually create more biodegradable products and reduce the long-term environmental burden of plastic waste.