Antarctic Polyester Hydrolases Degrade Aliphatic and Aromatic Polyesters at Moderate Temperatures

Area of Science:

• Biochemistry and Molecular Biology
• Environmental Microbiology
• Biotechnology and Bioremediation

Background:

• Polyethylene terephthalate (PET) is a prevalent plastic pollutant due to its environmental persistence.
• Enzymatic depolymerization offers a promising route for PET biodegradation and recycling.
• Most known PET hydrolases are thermophilic, requiring high temperatures (60-70°C) for efficient activity.

Purpose of the Study:

• To identify and characterize novel psychrophilic enzymes capable of degrading polyethylene terephthalate (PET) at low temperatures.
• To investigate the potential of Antarctic microorganisms as a source for cold-active PET-degrading enzymes.
• To explore the presence of further candidate psychrophilic PET hydrolases in Antarctic metagenomic data.

Main Methods:

• Biochemical characterization of polyester hydrolases (Mors1 and OaCut) from Antarctic bacteria (Moraxella sp. TA144 and Oleispira antarctica RB-8).
• Assay of enzymatic activity on aliphatic polyester polycaprolactone and aromatic polyester PET at 25°C.
• Comparative modeling of the Mors1 active site and bioinformatic analysis of Antarctic metagenomic samples.

Main Results:

• Polyester hydrolases Mors1 and OaCut demonstrated the ability to hydrolyze both polycaprolactone and PET at a mesophilic temperature of 25°C.
• Mors1 exhibited PET-degrading activity, causing weight loss in amorphous PET films, confirming its status as a psychrophilic PET hydrolase.
• Bioinformatic analysis revealed candidate genes for psychrophilic PET hydrolases within the Moraxellaceae family in Antarctic metagenomic data.

Conclusions:

• Antarctic bacteria harbor enzymes, such as Mors1, capable of efficiently degrading PET at low temperatures.
• The discovery of psychrophilic PET hydrolases expands the range of biocatalysts available for plastic biorecycling under mild conditions.
• Antarctic metagenomic data suggests a broader potential for discovering novel cold-active plastic-degrading enzymes.