Pac-Man Enzyme Breaks Down Bioplastics and Antibiotics, Scientists Find

Scientists at the University of Konstanz have discovered a novel "Pac-Man enzyme" that can break down several types of bioplastics within 250 to 330 days and also cleave beta-lactam antibiotics[1][2][7][8]. This discovery, announced on September 2, 2026, reveals a dual environmental function for a single enzyme[6][8].

This enzyme provides new insight into how microorganisms adapt to synthetic materials, opening doors for developing strategies to combat plastic waste. The enzyme's ability to neutralize antibiotics also points to a potential link between plastic degradation and the environmental spread of antibiotic resistance[1][2][6].

What the records show

Microbiologist Harry Lerner, then a postdoctoral researcher at the University of Konstanz, and Professor David Schleheck led the research that identified this enzyme[2][9]. Their findings were published in The ISME Journal on September 2, 2026[6][8]. The enzyme, dubbed the "Pac-Man enzyme" due to its wide-open active site, is a bacterial family-VIII esterase[2][8][11]. It is held firmly to the bacterial cell surface by a lipid anchor, which may prevent its loss in aquatic environments and increase catalytic efficiency[8][11].

The discovery originated from experiments where thin films of long-chain aliphatic polyesters (LCAP), a plant-oil-based bioplastic developed by chemist Stefan Mecking's team, were buried in the humus layer of the university's botanical garden forest[2][7][9][12]. Parallel laboratory experiments involved mixing powdered plastics into soil samples and monitoring carbon dioxide release, which signals microbial consumption[7][12]. Microscopic images of retrieved plastic films showed tiny, bacteria-shaped pits, indicating microbial activity[5][7][9].

In soil tests, the "Pac-Man enzyme" facilitated the complete degradation of several bioplastic materials, including LCAP, PHBV, and PCL, within approximately 250 to 330 days[7]. In contrast, conventional high-density polyethylene (HDPE) plastics remained largely unchanged under the same conditions[7]. Beyond plastic degradation, the enzyme also cleaves beta-lactam antibiotics such as penicillin G and ampicillin, rendering them unable to kill bacteria in laboratory settings[4][9]. This dual activity is attributed to its structural similarity to beta-lactamases, which are enzymes bacteria use to neutralize antibiotics[8][11].

The timeline

The research involved both field and laboratory experiments, including burying bioplastics in soil for a year[7][12]. The study's results were published in The ISME Journal on September 2, 2026, and simultaneously announced by the University of Konstanz[6][8].

What changed and for whom

This discovery provides a new foundation for future research into microbial plastic degradation and understanding the spread of antibiotic resistance in the environment[6]. The findings emphasize that a plastic's chemical composition and its disposal environment dictate whether microbes can effectively break it down[7]. Professor David Schleheck advocated for designing polymers with specific biochemical weak points that microbes can target for degradation[1][2]. This approach could lead to more truly biodegradable materials.

What the subject has said publicly

Harry Lerner explained that the humus layer, where the bioplastic films were buried, is a natural environment for the breakdown of cellulose and other natural polymers[9][12]. Professor David Schleheck highlighted the broader implication of the research, stressing the importance of designing polymers with inherent biochemical weaknesses that microbes can exploit[1][2]. However, the researchers cautioned that while the enzyme can chemically break down penicillin in a laboratory setting, this does not confirm it provides antibiotic resistance to living bacteria in their natural environment; this remains a hypothesis[1][4].

What we could not confirm

It could not be confirmed whether the "Pac-Man enzyme" provides antibiotic resistance to living bacteria in their natural environment, as this is currently a hypothesis[1][4]. The behavior of the enzyme in open environmental conditions or at an industrial scale also remains unknown[8].