Enzyme-embedded polyesters for accelerated biodegradation in the deep sea

The accumulation of persistent plastics in the ocean is causing wide-ranging environmental problems^1-3. Some commercially available compostable plastics^4-7, developed to address these issues, degrade efficiently under industrial composting conditions; however, their degradation in marine environments, particularly in the deep sea, remains limited^8-10. Here we demonstrate that thermally embedding enzymes into compostable polyesters (poly(butylene succinate) (PBS), poly(butylene succinate-co-adipate) (PBSA), poly(ε-caprolactone) (PCL) and poly(butylene adipate-co-terephthalate) (PBAT)) significantly accelerates their degradation in both coastal and deep-sea environments from water depths of 2-6 m to 5,503 m. Enzyme-embedded polyesters achieved near-complete degradation at a deep-sea depth of 757 m within 5 months. Furthermore, moderate biodegradation of enzyme-embedded polyesters was observed under extreme conditions on deep-sea floors of 5,503 m. In coastal seawater, films embedded with trace amounts (0.1 wt%) of enzyme underwent rapid degradation. The mechanical properties of enzyme-embedded polyesters were similar to those of enzyme-free polyesters. Chemical analysis confirmed the formation of low-molecular-mass degradation products and biochemical oxygen demand measurements supported the mineralization of the enzyme-embedded polyesters. The enzyme-embedding strategy enables enhanced marine degradation of compostable polyesters and represents a potential solution to marine plastic pollution.