Compostable plastics in marine environment

The bestselling compostable plastics are polylactic acid (PLA) and polybutylene adipate-co-terephthalate (PBAT). These plastics are biodegradable in industrial compost conditions but their degradation and colonization by the microbial community is poorly documented. To better understand their degradation in marine environment as well as the dynamics of bacterial colonization of these plastics after a long time of immersion (99 days, 160 days and 260 days), compostable (PBAT, semi-crystalline and amorphous PLA) and non-compostable plastic (polystyrene) were immerged in marine aquarium. 16S rRNA amplicon sequencing and chemical analysis were used to characterize these samples. Moreover, the influence of the temperature on plastic degradation was investigated in artificial water. PBAT had a significative weight lost reaching 3% after 260 days of immersion, unlike other polymers having stable weight. Chemical parameters varied for the three compostable plastics but the degradation was very slow. The temperature, an abiotic parameter, significantly influenced the plastic degradation, with a better degradation for higher temperature. Finally, microbial community structure varied according the immersion time with a high proportions of Archeae, while the plastisphere structure of PBAT was specific. However, a core of microbial microorganisms was observed on all the plastics and after the three immersion times. A better understanding of compostable plastic degradability in marine environment is crucial to evaluate their impact on the environment and to eco-design new recyclable plastics with optimal properties degradation.

当前主流可堆肥塑料为聚乳酸（polylactic acid, PLA）与聚己二酸/对苯二甲酸丁二醇酯（polybutylene adipate-co-terephthalate, PBAT）。该类塑料可在工业堆肥条件下实现生物降解，但目前关于其降解过程与微生物群落定殖的相关研究记载仍较为匮乏。
为深入解析这类塑料在海洋环境中的降解特性，以及长期浸泡（99天、160天、260天）后塑料表面细菌定殖的动态变化，研究人员将可堆肥塑料（PBAT、半结晶聚乳酸与无定形聚乳酸）及非可堆肥塑料（聚苯乙烯，polystyrene）浸没于海洋水族箱中。研究采用16S rRNA扩增子测序（16S rRNA amplicon sequencing）与化学分析技术对样本进行表征。
此外，研究还在人工水环境中探究了温度对塑料降解的影响。结果显示，浸泡260天后PBAT的质量损失显著，可达3%，而其余聚合物的质量均保持稳定。三种可堆肥塑料的化学参数均发生改变，但整体降解速率极慢。
作为非生物参数的温度，对塑料降解具有显著调控作用：温度越高，降解效果越好。最终，微生物群落结构随浸泡时长发生显著变化，古菌（Archeae）占比居高；而PBAT表面的塑料圈（plastisphere）群落结构具有特异性。不过，在所有塑料样本及三个浸泡时长的样本中，均观测到核心微生物类群的存在。
深入了解可堆肥塑料在海洋环境中的降解性能，对于评估其环境影响，以及生态设计具备最优降解性能的新型可回收塑料至关重要。