Abstract
With macroscopic litter and its degradation into secondary microplastic as a major source of environmental pollution, one key challenge is understanding the pathways from macro- to microplastic by abiotic and biotic environmental impact. So far, little is known about the impact of biota on material properties. This study focuses on recycled, bottle-grade poly(ethylene terephthalate) (r-PET) and the degrading enzyme PETase from Ideonella sakaiensis. Compact tension (CT) specimens were incubated in an enzymatic solution and thermally and mechanically characterized. A time-dependent study up to 96 h revealed the formation of steadily growing colloidal structures. After 96 h incubation, high amounts of BHET dimer were found in a near-surface layer, affecting crack propagation and leading to faster material failure. The results of this pilot study show that enzymatic activity accelerates embrittlement and favors fragmentation. We conclude that PET-degrading enzymes must be viewed as a potentially relevant acceleration factor in macroplastic degradation.
Highlights
Since the discovery of microplastics (MPs) in 2004 [1], particles have been detected in almost every natural environment
This study focuses on recycled, bottle-grade poly(ethylene terephthalate) (r-polyethylene terephthalate (PET)) and the degrading enzyme PETase from Ideonella sakaiensis
We conclude that PET-degrading enzymes must be viewed as a potentially relevant acceleration factor in macroplastic degradation
Summary
Since the discovery of microplastics (MPs) in 2004 [1], particles have been detected in almost every natural environment. Primary MP is already produced on a micrometer scale, whereas secondary MP arises by degradation and fragmentation of macroplastic. As the amount of secondary MP to be found in nature is drastically larger than that of primary MP, the degradation of macroplastic has recently gained new attention [2,3,4]. Polymers are exposed to a range of external environmental impacts. These can be categorized as abiotic factors such as UV-radiation, temperature, humidity, and mechanical stress, and biotic factors such as living or dead organisms, e.g., biofilm formation by bacteria, fungi, algae, or ingestion [5,6]. It is evident that material properties decisively influence the fragmentation towards MP and dramatically change during this process, creating a feedback loop on the degradation itself
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