Unveiling the spatial architecture of biodegradable polyester plastisphere in soil and its implications for organic matter composition

Abstract

Biodegradable plastics (BPs) are increasingly presented as sustainable alternatives to conventional plastics; however, their ecological effects on soils are poorly understood. BPs can alter soil microbiomes and nutrient cycling; yet, the extent, dynamics, and effects of the plastisphere on soil organic matter (SOM) after biodegradation remain underexplored. This study characterized the microbial plastisphere of three BPs, poly-3-hydroxybutyrate (PHB), poly(butylene succinate-co-adipate) (PBSA), and polybutylene adipate terephthalate (PBAT), and measured polymer biodegradation to link microbial dynamics with material breakdown. Metagenomics, scanning electron microscopy, and thermogravimetric analysis showed that these polymers formed structured plastispheres that significantly altered microbial communities and SOM. Each polymer hosted a distinct plastisphere; bacterial communities diverged more strongly between polymers than fungal ones. Functional profiling revealed shifts in nitrogen metabolism and ecological strategies at BP surfaces, including a decrease in nitrifiers and an increase in parasitic/pathogenic fungi. The plastisphere extended up to 1.25 mm for bacteria and 2.75 mm for fungi. PHB plastispheres were enriched in Comamonadaceae , Oxalobacteriaceae , and Rhodocyclaceae ; PBAT favored Xanthobacteraceae and Burkholderiaceae ; Xanthomonadaceae colonized all BPs. Fungal communities were dominated by Nectriaceae , Herpotrichiellaceae , and Aspergillaceae , and their composition changed over time. BP exposure reduced SOM, most strongly for PHB and PBSA, and to a lesser extent for PBAT, suggesting a positive priming effect. Overall, BP degradation promoted nitrogen-limited conditions and host-dependent microbial strategies. Although plastisphere communities showed signs of stabilization after 350 days, full recovery of microbial composition and SOM may require longer, indicating potential long-term impacts of BPs on soil ecosystems. These results underscore that BPs can alter soil microbial ecology and organic matter turnover, highlighting the need for further long-term studies.