Recently, the research team led by Professor Li Juying at Shenzhen University published a paper titled "Soil Type Governs the Degradation Dynamics and Microbial Assimilation of Biodegradable Plastic Polybutylene Adipate Terephthalate" in Environmental Science & Technology (Impact Factor: 12.2, CAS Q1, Nature Index journal). PhD student Zhang Xinyu served as the first author, while Professor Li Juying was the corresponding author. The findings break the traditional perception that "biodegradable" equals "risk-free," revealing that the degradation and mineralization of PBAT mulch films are highly dependent on soil conditions, and that their physical form alone can disturb microbial communities, thereby providing a new basis for the risk-zoning management of biodegradable mulch films, shifting from a material-oriented to a material × soil adaptation approach.

Biodegradable plastics such as polybutylene adipate terephthalate (PBAT) are being widely promoted as substitutes for conventional plastics. However, systematic understanding remains lacking regarding how different soil conditions affect their degradation efficiency, whether complete films and microplastic fragments differ in their impacts on microbial communities, and which metabolic pathways and functional genes dominate the mineralization process. This study integrates metagenomics, microbial community analysis, and strain isolation to investigate the degradation mechanisms of PBAT in 10 different agricultural soils. The results indicate that soil properties are critical factors regulating the environmental fate of PBAT. Among them, neutral-to-alkaline silty loam soils exhibited the highest degradation efficiency. Soil physicochemical properties can indirectly regulate PBAT weight loss by altering the abundance of genes related to hydrolases and aromatic compound degradation enzymes; soil nitrogen content was identified as a key regulatory factor. Metagenomic correlation analysis further revealed that PBAT degradation is closely associated with specific microbial communities, including the genus Hydrogenophaga and fungi of the phylum Ascomycota. Compared with complete films, PBAT microplastic particles exerted stronger disturbances on soil microorganisms, manifested as a significant decline in microbial diversity, restructuring of community composition, and shifts in functional gene composition. The study further elucidated the complete degradation pathway of PBAT, including initial polymer chain scission and subsequent microbial assimilation of terephthalic acid via the β-ketoadipate pathway. This research reveals the degradation mechanisms of PBAT in soil from three dimensions—soil type, functional genes, and microbial metabolic pathways—providing a mechanistic basis for environmental risk assessment and sustainable management of biodegradable plastics.

This study reveals that the degradation and mineralization of PBAT mulch films are highly dependent on soil conditions, and their environmental risks cannot be simply evaluated as "biodegradable." The findings show that neutral-to-alkaline soils with suitable water-holding capacity and nutrient conditions are more favorable for PBAT degradation, while low-potential regions require more cautious assessment of residual risks. Meanwhile, "biodegradable" does not equate to "no microplastic risk"—if fragmentation outpaces mineralization,阶段性 or even long-term microplastic accumulation may still occur. Furthermore, even with identical chemical composition, PBAT microplastics exert significantly stronger disturbances on soil bacterial and fungal communities than complete films, indicating that physical form itself is an important ecological risk factor. Accordingly, the study proposes that biodegradable mulch film management should shift from material-oriented to material × soil adaptation, conducting regional adaptation and risk zoning based on soil pH, texture, water-holding capacity, and nitrogen content, to promote the truly environmentally friendly application of PBAT mulch films.

This work was supported by grants from the National Natural Science Foundation of China (Nos. 22576140 and 42377025) and the Science Foundation Project of South China University of Technology (No. x2hj-D6242050).

Original article: https://doi.org/10.1021/acs.est.6c11170.