Biodegradation of PHB/PBAT films and isolation of novel PBAT biodegraders from soil microbiomes

• Published in: Chemosphere (Oxford) Vol. 362; p. 142696
• Main Authors: Fernandes, Miguel, Salvador, Andreia F., Vicente, António A.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.08.2024
• Subjects: 16S/18S rRNA amplicon sequencing; Aspergillus pseudodeflectus; Polybutylene adipate terephthalate (PBAT) biodegradation; Polyhydroxybutyrate (PHB) biodegradation; Purpureocillium lilacinum; Soil microbiome; Soil microbiome; Aspergillus pseudodeflectus; Polyhydroxybutyrate (PHB) biodegradation; 16S/18S rRNA amplicon sequencing; Polybutylene adipate terephthalate (PBAT) biodegradation; Purpureocillium lilacinum
• ISSN: 0045-6535; 1879-1298; 1879-1298
• DOI: 10.1016/j.chemosphere.2024.142696

Polyhydroxyalkanoates (PHAs) are important candidates for replacing petroleum-based plastics. This transition is urgent for the development of a biobased economy and to protect human health and natural ecosystems. PHAs are biobased and biodegradable polyesters that when blended with other polymers, such as poly(butylene adipate-co-terephthalate) (PBAT), acquire remarkable improvements in their properties, which allow them to comply with the requirements of packaging applications. However, the biodegradation of such blends should be tested to evaluate the impact of those polymers in the environment. For instance, PBAT is a compostable aliphatic-aromatic copolyester, and its biodegradation in natural environments, such as soil, is poorly studied. In this work, we evaluated the biodegradation of a bilayer film composed of PHB and PBAT, by a soil microbiome. The bilayer film reached 47 ± 1 % mineralization in 180 days and PHB was no longer detected after this period. The increased crystallinity of the PBAT residue was a clear sign of biodegradation, indicating that the amorphous regions were preferentially biodegraded. Seven microorganisms were isolated, from which 4 were closely related to microorganisms already known as PHB degraders, but the other 3 species, closely related to Streptomyces coelicoflavus, Clonostachys rosea and Aspergillus insuetus, were found for the first time as PHB degraders. Most remarkably, two fungi closely related to Purpureocillium lilacinum and Aspergillus pseudodeflectus (99.83 % and 100 % identity by ITS sequencing) were isolated and identified as PBAT degraders. This is very interesting due to the rarity of isolating PBAT-degrading microorganisms. These results show that the bilayer film can be biodegraded in soil, at mesophilic temperatures, showing its potential to replace synthetic plastics in food packaging. [Display omitted] •The biodegradation of the PHB layer was faster than the PBAT layer in soil.•The crystallinity increased was a clear sign of biodegradation.•Seven microorganisms were isolated as capable of degrading PHB.•Purpureocillium lilacinum and Aspergillus pseudodeflectus were able to degrade PBAT.