Bacterial Community and Predicted Functional Gene Dynamics Relevant to the Potential Biodegradation of Polybutylene Adipate Terephthalate (PBAT)

Polybutylene adipate terephthalate (PBAT) is a widely used biodegradable plastic, but its microbial degradation mechanisms and environmental responses remain poorly understood. In this study, two compost inocula (K and I) were used to establish PBAT enrichment cultures under mesophilic (35 °C, M) and thermophilic (58 °C, T) conditions, and the effects of temperature and inoculum source on bacterial community structure and PICRUSt2-derived predicted functional profiles were investigated. Surface analyses revealed cracking, erosion, and structural collapse of PBAT under all conditions, with more pronounced degradation in compost I-derived cultures. Microbial diversity decreased during enrichment, accompanied by dominance of specific genera. Under mesophilic conditions, Pseudoxanthomonas dominated (72.6%–91.0%) and showed strong positive correlations with predicted ester bond hydrolysis-related KOs ( p < 0.05), suggesting a potential association with initial hydrolysis. Under thermophilic conditions, compost K cultures were dominated by Thermoflavifilum and Rhodothermus , which were mainly associated with predicted hydrolysis-related KOs, whereas compost I cultures were dominated by Thermoflavifilum and Thermopolyspora and showed stronger associations with predicted KOs related to adipate and terephthalic acid metabolism. Predicted aromatic intermediate metabolism-related KOs, including K04101, K01055, and K01607, were also higher in compost I-derived thermophilic cultures. Overall, temperature and inoculum composition jointly shaped bacterial community assembly and predicted PBAT degradation-related functional potential. Thermophilic conditions combined with compost I were associated with functionally differentiated bacterial communities and higher predicted potential for downstream PBAT-derived intermediate metabolism. These findings provide a microbial ecological basis for temperature- and inoculum-guided enrichment strategies to improve PBAT biodegradation and biodegradable plastic waste treatment.