Long-term immersion of compostable plastics in marine aquarium: Microbial biofilm evolution and polymer degradation

The best-selling compostable plastics, polylactic acid (PLA) and polybutylene adipate-co-terephthalate (PBAT), can accidentally end up in the marine environment due to plastic waste mismanagement. Their degradation and colonization by microbial communities are poorly documented in marine conditions. To better understand their degradation, as well as the dynamics of bacterial colonization after a long immersion time (99, 160, and 260 days), PBAT, semicrystalline, and amorphous PLA films were immersed in a marine aquarium. Sequencing and chemical analyses were used in parallel to characterize these samples. Despite the variation in the chemical intrinsic parameters of these plastics, their degradation remains very slow. Microbial community structure varied according to the immersion time with a high proportion of Archaea. Moreover, the plastisphere structure of PBAT was specific. A better understanding of compostable plastic degradability is crucial to evaluate their impact on ecosystems and to eco-design new recyclable plastics with optimal degradation properties.

Automated summary

The best-selling compostable plastics, PLA and PBAT, can enter the marine environment accidentally due to mismanagement of plastic waste. However, their degradation and colonization by microbial communities in marine conditions are not well-documented. In this study, PBAT, semicrystalline, and amorphous PLA films were immersed in a marine aquarium for 99, 160, and 260 days to investigate their degradation and bacterial colonization. The results showed that degradation of these plastics was slow and the microbial community structure varied with immersion time, with a high proportion of Archaea. Understanding the degradability of compostable plastics is crucial for assessing their impact on ecosystems and designing new recyclable plastics with optimal degradation properties.