Biodegradation analysis of PHBV/PBAT bilayer films produced industrially

In the last years, several biodegradable polymers have been tested as alternatives to petrochemical polymers. Many blends and composites have been developed, to comply with environment and industrial demands. However, biodegradation of these plastic blends should be tested for their effective biodegradation in natural environments. Polyhydroxybutyrate-co-hydroxyvalerate/Polybutylene adipate terephthalate (PHBV/PBAT) bilayer films are examples of such blends, presenting attractive physical/chemical properties, which make them interesting for food packaging applications. In this work, the aerobic biodegradation of PHBV/PBAT bilayer films in soil at 27 °C was determined by following CO₂ production using the ASTMD5988 (2018) test method. After 7 months, the bilayer film reached 46.0 ± 2.7% of biodegradation. All the physicochemical analyses indicated that the PHBV layer was not present in the residues after the biodegradation experiment. The residues were composed exclusively of PBAT and presented an increase in crystallinity, and a reduction of the carbonyl peak suggesting morphological and chemical changes possibly related to biotic processes. A biofilm containing filamentous fungi was developed on the residues surface. Microbial isolates with the ability to biodegrade PBAT could not be obtained. On the other hand, 12 microbial isolates were identified as PHBV degraders, including two fungi assigned to Aspergillus species (100% identity at the ITS level), which were not previously described as PHBV degraders.