Biologists studying how bacteria break down a new generation of plant-based bioplastics (long-chain aliphatic polyesters) have discovered an enzyme that can break down both plastics and antibiotics.
SEM images of LCAP films incubated in pristine forest soil for over 1 year. The arrow in panel (d) points to an object within the cavity that may represent a (damaged) microbial cell. However, these were found very rarely. Empty cavities were more representative (ac). Image credit: Lerner others., doi: 10.1093/ismejo/wrag203.
“Plastic waste and its degradation into micro- and nanoplastics, combined with the slow biodegradation of most current plastic materials, is developing into a major concern for the environment and human health,” said lead author Dr. Harry Lerner from the University of Konstanz and his colleagues.
“Plastic debris is not only a recalcitrant physical contaminant, but can also carry chemical contaminants and act as a vector for microbial colonization.”
“Furthermore, microorganisms living in the plastisphere, a biofilm community on plastic surfaces, have been shown to carry disproportionately high levels of antibiotic resistance genes, raising concerns that antibiotic resistance genes may spread throughout ecosystems through plastics.”
In the study, researchers buried strips of a biodegradable plastic called LCAP, made from long-chain molecules derived from vegetable oils, in forest soil for over a year.
Subsequent microscopic images showed that the plastic was full of tiny holes in the shape of bacteria, evidence of microorganisms eating away at the surface.
“We buried small pieces of LCAP bioplastic film about 10 centimeters deep above the humus layer in the university’s botanical garden forest,” Dr. Lerner said.
“This layer is where the breakdown of cellulose and other natural polymers such as cutin, a plant-based polyester, occurs.”
By sequencing the DNA of soil microorganisms that grow on plastic, researchers identified a bacterial enzyme that closely resembles a class of proteins that bacteria use to defeat penicillin antibiotics, which they named LCPH1.
Structural modeling revealed that the enzyme has an unusually wide and open active site, called a “Pac-Man” shape, that can trap both plastic chains and antibiotic molecules.
The enzyme also broke down bioplastics into their constituent parts, destroyed penicillin and ampicillin, and even took away the drug’s ability to kill bacteria.
The findings raise provocative questions for the growing field of plastic pollution research.
“The structure of this enzyme is similar to that of esterases, but also to that of beta-lactamase, a bacterial enzyme that can cleave the beta-lactam ring of certain antibiotics, such as penicillin, making bacteria resistant to antibiotics,” Dr. Lerner said.
“The plastisphere is a new habitat in our environment,” added Dr. David Schleheck, senior author of the study.
“It’s only in the last 50 to 75 years that humans have started introducing large amounts of plastic into the environment.”
“Since then, it has theoretically been possible for microbial communities such as bacteria, yeast, and fungi to use this as an additional source of carbon and energy for their growth.”
“In theory, they would certainly like to use plastic as a growth substrate, but in practice they can’t do that because the material is indigestible to microbial metabolism and therefore hardly degraded.”
“We think this is encouraging, because bacteria seem to be able to adapt to breaking down polyester plastics faster than we expected.”
“To tackle the environmental problem of plastic pollution, we humans need to harness the power of microorganisms.”
“Ideally, we would only use polymers with biochemical break points, such as the hydrolyzable ester linkages in polyesters like LCAP and other types of bioplastics.”
team’s paper Published this month ISME Journal.
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harry lerner others. 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
