Scientists have discovered a bacterial enzyme that can break down biodegradable plant-based bioplastics and deactivate penicillin-type antibiotics, offering new insights into plastic pollution and antibiotic resistance.
Scanning electron microscopy images of LCAP films incubated in pristine forest soil for more than one year. The arrow in panel (d) points to an object inside a cavity that may represent a damaged microbial cell. However, such objects were rare, while empty cavities were more common. Image credit: Lerner et al., doi: 10.1093/ismejo/wrag203.
“Plastic waste and the breakdown of plastic materials into microplastics and nanoplastics are becoming major concerns for the environment and human health,” said lead author Dr. Harry Lerner, a researcher at the University of Konstanz, and his colleagues.
“Plastic debris is not only a persistent physical contaminant. It can also carry chemical pollutants and provide a surface for microbial colonization.”
“Microorganisms living in the plastisphere—the biofilm community that develops on plastic surfaces—have also been shown to carry disproportionately high levels of antibiotic resistance genes. This raises concerns that plastics could help spread antibiotic resistance throughout ecosystems.”
To investigate how microorganisms degrade new biodegradable plastics, the researchers buried strips of LCAP, a bioplastic made from long-chain molecules derived from vegetable oils, in forest soil for more than one year.
Microscopic analysis revealed that the plastic surface had developed numerous tiny, bacteria-shaped cavities. The findings provided evidence that microorganisms had colonized the material and consumed parts of the plastic.
“We buried small pieces of LCAP bioplastic film approximately 10 centimeters deep, above the humus layer, in the forest of the university’s botanical garden,” Dr. Lerner said.
“This is the layer where cellulose and other natural polymers, including cutin—a plant-based polyester—are broken down.”
By sequencing DNA from microorganisms growing on the plastic, the scientists identified a bacterial enzyme that resembles proteins used by bacteria to resist penicillin antibiotics. They named the enzyme LCPH1.
Structural modeling showed that LCPH1 has an unusually wide and open active site. The researchers described its shape as resembling a “Pac-Man,” allowing it to capture and break down both polyester chains and antibiotic molecules.
Laboratory experiments showed that LCPH1 degraded LCAP bioplastics into their component parts. The enzyme also broke down penicillin and ampicillin, eliminating the drugs’ ability to kill bacteria.
The discovery highlights a possible connection between the biodegradation of plastic and the development of antibiotic resistance in microbial communities.
“The structure of this enzyme is similar to esterases, but it also resembles beta-lactamase, a bacterial enzyme that can cleave the beta-lactam ring found in antibiotics such as penicillin,” Dr. Lerner said.
“By breaking this ring, beta-lactamase enzymes can make bacteria resistant to these antibiotics.”
“The plastisphere is a new habitat in our environment,” said senior author Dr. David Schleheck, also from the University of Konstanz.
“Humans have only been introducing large quantities of plastic into the environment for approximately 50 to 75 years.”
“Since then, microbial communities—including bacteria, yeasts, and fungi—have theoretically had the opportunity to use plastic as an additional source of carbon and energy.”
“In practice, however, most plastic materials are difficult for microorganisms to digest and are therefore degraded very slowly.”
“We believe these findings are encouraging because bacteria appear capable of adapting to the breakdown of polyester plastics more quickly than expected.”
“To address the environmental threat posed by plastic pollution, we need to harness the natural abilities of microorganisms.”
“Ideally, future materials will contain biochemical weak points, such as hydrolyzable ester bonds found in polyesters like LCAP and other biodegradable plastics.”
The team’s paper was published this month in the ISME Journal.
_____
Lerner, H. et al. 2026. Bacterial family VIII esterases exhibit dual activities of hydrolysis of polyester bioplastics and β-lactam antibiotics. ISME Journal 20 (1): wrag203; doi: 10.1093/ismejo/wrag203.
Source: www.sci.news