Functional dynamics and interactions within the bacterial community responsible for biodegradable plastic degradation during aerobic composting
Though biodegradable plastics have been widely developed as sustainable alternatives to petroleum-based plastics, their degradation behavior and microbial interactions in composting environments remain insufficiently understood. In this study, the degradation characteristics of polyhydroxybutyrate (PHB), polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), and polybutylene succinate (PBS), and the interactions between bacterial communities and functional genes, were evaluated in a 41-day aerobic composting system using anaerobically digested sewage sludge as substrate. Composting parameters were similarly affected by all biodegradable plastics, and the final compost reached a Solvita compost maturity index of 8.0 with no detectable pathogenic bacteria and a CO2 index of 7.83, indicating stable composting. After 41 days of composting, microcracks and microbial attachment were observed on all biodegradable plastic surfaces, with PHB and PBAT showing the most pronounced structural damage and biofilm formation, whereas microbial attachment to PLA was limited. Although biodegradable plastic addition did not greatly alter the overall bacterial community structure, it selectively promoted specific bacterial genera (Symbiobacterium, Paenibacillus, and Psychrobacillus). PICRUSt2-based functional gene prediction revealed that PHB degradation-related genes exhibited the highest predicted abundance, whereas PLA- and PBS-related genes showed low abundance, indicating differences in functional degradation potential among plastic types. Positive correlations among esterase- and hydrolase-related genes under biodegradable plastic-amended conditions suggest that coordinated microbial functional responses to biodegradable plastic addition. Network analysis further indicated that biodegradable plastic addition influenced interactions between specific bacterial genera and degradation-related functional genes. Overall, this study provides insights into bacterial functional adaptation during biodegradable plastic degradation under aerobic composting conditions.