Occurrence and Analysis of Thermophilic Poly(butylene adipate-co-terephthalate)-Degrading Microorganisms in Temperate Zone Soils

The ubiquity and character of thermophilic poly(butylene adipate-co-terephthalate) (PBAT)-degrading microorganisms in soils were investigated and compared to the process in an industrial composting plant. PBAT degraders were sought in 41 temperate zone soils. No mesophilic degraders were found by the employed method, but roughly 102 colony-forming units (CFUs) of thermophilic degraders per gram of soil were found in nine soils, and after an enrichment procedure, the PBAT-degrading consortia were isolated from 30 out of 41 soils. Thermophilic actinomycetes, Thermobispora bispora in particular, together with bacilli proved to be the key constituents of the isolated and characterized PBAT-degrading consortia, with bacilli comprising from about 30% to over 90% of the retrieved sequences. It was also shown that only consortia containing both constituents were able to decompose PBAT. For comparison, a PBAT film together with two types of PBAT/starch films were subjected to biodegradation in compost and the degrading microorganisms were analyzed. Bacilli and actinobacteria were again the most common species identified on pure PBAT film, especially at the beginning of biodegradation. Later, the composition of the consortia on all three tested materials became very similar and more diverse. Since waste containing PBAT-based materials is often intended to end up in composting plants, this study increases our confidence that thermophilic PBAT degraders are rather broadly present in the environment and the degradation of the material during the composting process should not be limited by the absence of specific microorganisms.