Deep-sea enzyme capable of breaking down plastic waste, find German researchers

28 Sep 2023 --- Researchers at Kiel University, Germany, in collaboration with scientists from the University of Hamburg and the Heinrich-Heine-University Düsseldorf, have discovered a deep-sea enzyme from archaeal origin that hydrolyzes PET polymer.

Until now, most PET-degrading enzymes have been found in bacteria or fungi, the researchers state. However, this new study has identified and biochemically described the PET-degrading enzyme PET46 from a non-cultured deep-sea microorganism. 

“In our study, we have discovered a new genetic resource from deep-sea organisms belonging to the archaea,” says professor Ruth Schmitz-Streit, head of the Molecular Biology of Microorganisms working group at the Institute of General Microbiology and member of the research priority area Kiel Marine Science at Kiel University.

“Our data contribute to a better understanding of the ecological role of deep-sea archaea and the possible degradation of PET waste in the sea,” says the microbiologist.

Deep-sea microorganism
PET46 has unique properties, including the ability to degrade both long-chain PET molecules (polymers) and short-chain PET molecules (oligomers). This continuous degradation capability sets PET46 apart from previously known enzymes.

Furthermore, PET46 employs a distinct mechanism for substrate binding compared to other PET-degrading enzymes. It features a lid of 45 amino acids above the enzyme’s active center, which is crucial for binding. In contrast, other PET enzymes typically have aromatic amino acids near the active site.The structure of PET46 is similar to that of known enzymes such as IsPETase and LCC, but has unique features.

The structural and biochemical characteristics of PET46 make it a promising enzyme for various applications, such as addressing marine and terrestrial plastic pollution, the scientists highlight. PET46 is more efficient at 70 degrees Celsius than the best-known PET-degrading enzymes from bacteria and composting plants at their respective optimal temperatures.

“The degradation of PET through enzymatic hydrolysis has gained considerable attention as a promising approach to address the global plastic waste crisis,” the study states. 

“Our biochemical results significantly extend the knowledge of PETase enzymes and their biodiversity. Our study further enables the development of an expanded phylogenetic framework for identifying the diversity of putative PET-degrading enzymes in marine microbial groups throughout the global ocean. Finally, the data presented here will help advance our knowledge on the ecological role of the Bathyarchaeota and the possible decomposition of marine PET litter.”

The research was part of the Plastisea project funded by the German Federal Ministry of Education and Research.

Edited by Radhika Sikaria