Biodegradation of Synthetic Aliphatic-Aromatic Polyesters in Soils: Linking Chemical Structure to Biodegradability

Area of Science:

• Polymer Science and Engineering
• Environmental Science and Microbiology
• Biotechnology and Biodegradation

Background:

• Biodegradable aliphatic-aromatic copolyesters are crucial for sustainable applications, particularly soil-biodegradable mulch films.
• Understanding the relationship between copolyester chemical structure and soil biodegradability is essential for optimizing material design.
• Existing research highlights the need for detailed studies on how specific structural variations influence biodegradation rates and pathways.

Purpose of the Study:

• To investigate the impact of chemical structure, specifically terephthalate content, on the soil biodegradability of polybutylene adipate-co-terephthalate (PBAT) and polybutylene sebacate-co-terephthalate (PBSeT).
• To quantify the extent of mineralization and microbial incorporation of these copolyesters in soil environments.
• To establish structure-biodegradability relationships for tailoring copolyesters to specific environmental conditions and applications.

Main Methods:

• Utilized ¹³C-labeled PBAT and PBSeT variants with varying terephthalate (T) content, alongside ¹³C-labeled cellulose as a control.
• Assessed soil biodegradation by monitoring mineralization to ¹³CO₂ over multi-month incubations.
• Quantified non-mineralized polyester and determined ¹³C mass balances to ensure accurate assessment of degradation and incorporation.

Main Results:

• Polybutylene sebacate-co-terephthalate (PBSeT) exhibited higher soil biodegradability than polybutylene adipate-co-terephthalate (PBAT) at 50% terephthalate content.
• PBAT biodegradability significantly increased as terephthalate content decreased, with notable enhancement at 0% T.
• Decreasing terephthalate content promoted preferential biodegradation of aliphatic domains and increased incorporation of polyester carbon into soil microbial biomass.

Conclusions:

• Soil biodegradability of aliphatic-aromatic copolyesters is strongly influenced by their chemical structure, particularly terephthalate content.
• Reduced terephthalate content enhances the biodegradability of PBAT and leads to greater assimilation into the soil microbiome.
• Enzymatic hydrolyzability differences correlate with observed biodegradability, providing a basis for designing biodegradable polymers for specific environments.