Abstract

Degradation rate of poly(lactic acid) (PLA), a compostable plastic, is affected by its physical properties and environmental conditions. Since PLA with different physical properties enter composting systems, investigation of degradation of PLA with strong physical properties in compost at different temperatures and its influence on compost fungal community structure are the main concerns of this study. To determine the effect of slow PLA degradation on fungal communities, PLA granules with high degree of crystallinity, 60%, were incubated in compost at 25 °C and 50 °C for 4 months at 0, 10, 25 and 50% (w/w) concentrations; their degradation rates were compared and impact of PLA degradation on compost fungal communities was examined by terminal restriction fragment length polymorphism (TRFLP). PLA granules in compost at 25 °C showed no physical changes but at 50 °C physical disintegration occurred after 4 months. TRFLP revealed that fungal community profiles in compost were affected by PLA, particularly at 50 °C where PLA degraded. Compost fungal communities in the presence of PLA at 50 °C had more variation, 63%, than at 25 °C (52%). Incubation time affected fungal community structure as during 2nd month, community structure changed specifically at 50 °C and at 50% (w/w) PLA, however, became similar to that in the absence of PLA at the end of 4th month at both temperatures indicating PLA with a high degree of crystallinity causes a temporal perturbation in compost fungal communities. In compost containing PLA at 50 °C, abundance of certain TRFs representing fungal populations increased to 30% which may involve in PLA utilization.

摘要

聚乳酸 (PLA) 是一种可堆肥塑料，其降解率受其物理特性和环境条件的影响。由于具有不同物理性质的 PLA 进入堆肥系统，因此研究具有强物理性质的 PLA 在不同温度下在堆肥中的降解及其对堆肥真菌群落结构的影响是本研究的主要关注点。为了确定 PLA 缓慢降解对真菌群落的影响，将结晶度为 60% 的 PLA 颗粒在 25 °C 和 50 °C 的堆肥中以 0、10、25 和 50%（w/ w) 浓度；比较了它们的降解率，并通过末端限制性片段长度多态性 (TRFLP) 检查了 PLA 降解对堆肥真菌群落的影响。PLA 颗粒在 25 °C 的堆肥中没有显示出物理变化，但在 50 °C 下 4 个月后发生物理分解。TRFLP 显示堆肥中的真菌群落特征受 PLA 影响，尤其是在 50°C 时 PLA 降解。在 PLA 存在下，50 °C 下堆肥真菌群落比 25 °C (52%) 有更多的变化，63%。孵化时间影响真菌群落结构，因为在第 2 个月，群落结构在 50 °C 和 50% (w/w) PLA 下发生了特别的变化，然而，在第 4 个月末在两种温度下变得与没有 PLA 的情况相似表明具有高度结晶度的 PLA 会导致堆肥真菌群落的时间扰动。在 50 °C 时含有 PLA 的堆肥中，代表真菌种群的某些 TRF 的丰度增加到 30%，这可能涉及 PLA 的利用。