Discovery of Bioplastic Degrading Bacteria and Their Dual-Action Enzyme

Biologists have identified a novel enzyme that not only breaks down next-generation plant-based bioplastics but also dismantles antibiotics. This discovery marks a critical milestone in understanding both plastic pollution and antibiotic resistance.

Led by Dr. Harry Lerner from the University of Konstanz, a team of researchers investigated how bioplastic degrading bacteria process long-chain aliphatic polyesters (LCAP), a new generation of bioplastics derived from plant oils. Their study uncovered a surprising dual activity that highlights significant environmental and human health concerns regarding plastic waste.

The habitat of bioplastic degrading bacteria

During the experiment, the research team buried biodegradable LCAP plastic strips in the upper humus layer of the university’s botanical garden forest. The strips were placed about 10 centimeters deep, a zone where natural polymers like cellulose and plant-based cutin are actively broken down. After being incubated undisturbed for more than a year, microscopic images revealed tiny, bacteria-shaped pits on the plastic surface, proving that microbes had been actively eating away at the material.

Identifying the LCPH1 Enzyme: The “Pac-Man” Shape

By sequencing the DNA of the soil microbes thriving on the plastic surface, the scientists discovered a bacterial enzyme they named LCPH1. Structural modeling showed that the enzyme features an unusually wide, open active site—nicknamed a ‘pac-man’ shape. This unique structure allows it to grab both plastic strands and antibiotic molecules.

The enzyme efficiently breaks down the bioplastic into its component parts while simultaneously destroying penicillin and ampicillin. This action strips the drugs of their ability to kill bacteria. According to Dr. Lerner, the enzyme’s structure is similar to esterases as well as beta-lactamases. The latter are bacterial enzymes capable of cleaving the beta-lactam ring of penicillin-type antibiotics, thereby rendering the bacteria resistant.

The Plastisphere: A New Ecological Niche

The study raises serious concerns about the “plastisphere”—the biofilm community forming on plastic surfaces. Plastic debris acts as a recalcitrant physical pollutant and a vector for transporting chemical contaminants. The bioplastic degrading bacteria and other microorganisms inhabiting this space harbor disproportionately high levels of antibiotic resistance genes, facilitating their dissemination throughout ecosystems.

Dr. David Schleheck, the senior author of the study, noted that humans have been introducing plastic into the environment in significant quantities for only about 50 to 75 years. While microbes theoretically could use plastic as an additional carbon and energy source, most conventional materials are indigestible to their metabolism. However, it is encouraging that bacteria appear to adapt to breaking down polyester plastics faster than anticipated. To effectively tackle plastic pollution, the researchers suggest utilizing polymers with explicit biochemical breaking points, such as the hydrolysable ester bonds found in LCAP and similar bioplastics.

FAQ

How deep was the plastic buried during the experiment?

Researchers buried the small pieces of LCAP bioplastic film approximately 10 centimeters deep in the forest humus layer, leaving them there for more than a year.

What is the name of the newly discovered enzyme?

The scientists identified a bacterial enzyme named LCPH1, which features a wide, “Pac-Man” shaped active site capable of dismantling both plastics and antibiotics.

How long has significant plastic pollution been in our environment?

According to the study, humans have only been introducing plastic into the natural environment in significant quantities for about 50 to 75 years.

Related content from dontwasteit.hu: Phasing Out Fossil-Based Plastics Cannot Work Without a Bioplastics Strategy

Source:

Original study (The ISME Journal): DOI: 10.1093/ismejo/wrag203