Correlations among polylactic acid biodegradation, bacterial communities, and predicted functional genes under mesophilic and thermophilic composts

Abstract

As a sustainable alternative to petroleum-based plastics, biodegradable plastics such as polylactic acid (PLA) have garnered increasing attention. However, despite being the most widely used biodegradable plastic, studies investigating the post-use degradation of PLA remain limited. This study compared the degradation behavior of PLA samples under mesophilic (35 °C) and thermophilic (58 °C) compost conditions and analyzed associated changes in microbial communities and predicted functional genes throughout the degradation process. The PLA film was completely degraded within 15 days under thermophilic conditions, whereas only a 13.7 % weight loss was observed after 40 days under mesophilic conditions. For PLA granules, weight loss after 65 days reached 24.8 % and 6.1 % under thermophilic and mesophilic conditions, respectively. SEM and FTIR analyses confirmed evidence of microbial degradation, such as surface erosion and ester bond cleavage. Spearman's correlation analysis revealed that Bacillaceae-dominated microbial communities play an active role in PLA biodegradation in thermophilic environments, while Georgenia and Cupriavidus may function as potential PLA degraders in mesophilic environments. Functional gene prediction revealed that K01126 (glycerophosphodiester phosphodiesterase) and K01048 (lysophospholipase), both associated with PLA degradation, exhibited strong positive correlations with degradation rate, suggesting their key enzymatic roles in PLA hydrolysis. Furthermore, a promising PLA-degrading bacterium, Ralstonia sp. AF1, was isolated from compost following the degradation process. Overall, this study demonstrates the biodegradability of PLA under compost conditions through comprehensive analysis of degradation characteristics and bacterial community dynamics, and provides fundamental insights to enhance the degradation efficiency of PLA in compost environments. © 2026 Elsevier Ltd