This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: In the ocean, plastic waste collects to form large garbage patches that endanger marine life. This is partly because the synthetic plastic polymers used today can only be broken down biologically—that is, by microorganisms—at a very slow rate.
Instead, the physical fragmentation of these materials leads to the formation of microplastics and nanoplastics. However, microorganisms do colonize plastic waste in the environment, forming biofilms and creating a unique microbial habitat that researchers refer to as the "plastisphere." A research team at the University of Konstanz has identified a new enzyme that can not only degrade certain polyesters and bioplastics but also might provide bacteria with resistance to antibiotics. The discovery raises hopes that microorganisms can adapt to plastic degradation more rapidly than previously thought.
Due to its structure featuring a wide-open active site, the researchers have named this "plastic-eating" enzyme the "Pac-Man enzyme." Accelerating the environmental breakdown of plastic would require the use of biodegradable plastics wherever possible, as these materials can be decomposed by microorganisms. In their research project, biologists Harry Lerner and David Schleheck from Konstanz investigated the complete microbial degradation of bioplastics. At the same time, they analyzed both the composition and the complete genetic makeup (the metagenome) of the microbial community involved in this degradation.
For the study, the researchers used bioplastic materials—long-chain aliphatic polyesters (LCAP)—developed by chemist Stefan Mecking's team. Their joint study has now been published in the journal The ISME Journal. How did the research team conduct their study?
"We buried small pieces of LCAP bioplastic film in the upper humus layer in the forest at the university's botanical garden, about 10 centimeters (4 inches) deep," explains Lerner. "This layer is where the breakdown of cellulose and other natural polymers, such as cutin—a plant-based polyester—takes place." In the laboratory, the team also mixed bioplastic powder into samples of the same forest soil. The forest samples were left untouched for a whole year, while in the laboratory, CO2 production—and thus microbial respiration—was monitored in great detail over the course of one year to document the degradation of the materials.
"Cellulose, other types of bioplastics such as PHBV and PCL, as well as high-density plastic (HDPE) and untreated soil were used as controls in the laboratory. We found that all bioplastic materials were completely degraded within roughly 250 to 330 days. Cellulose broke down after about 80 days, whereas virtually no degradation occurred for HDPE," says Lerner.
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