Genome-Centric Metagenomics\nInsights into the Plastisphere-Driven\nNatural Degradation Characteristics and Mechanism of Biodegradable\nPlastics in Aquatic Environments

Biodegradable plastics (BPs) are pervasively available\nas alternatives\nto traditional plastics, but their natural degradation characteristics\nand microbial-driven degradation mechanisms are poorly understood,\nespecially in aquatic environments, the primary sink of plastic debris.\nHerein, the three-month dynamic degradation process of BPs (the copolymer\nof poly(butylene adipate-<i>co</i>-terephthalate) and polylactic\nacid (PLA) (PBAT/PLA) and single PLA) in a natural aquatic environment\nwas investigated, with nonbiodegradable plastics polyvinyl chloride,\npolypropylene, and polystyrene as controls. PBAT/PLA showed the weight\nloss of 47.4% at 50 days and severe fragmentation within two months,\nbut no significant decay for other plastics. The significant increase\nin the specific surface area and roughness and the weakening of hydrophobicity\nwithin the first month promoted microbial attachment to the PBAT/PLA\nsurface. Then, a complete microbial succession occurred, including\nbiofilm formation, maturation, and dispersion. Metagenomic analysis\nindicated that plastispheres selectively enriched degraders. Based\non the functional genes involved in BPs degradation, a total of 16\nhigh-quality metagenome-assembled genomes of degraders (mainly Burkholderiaceae)\nwere recovered from the PBAT/PLA plastisphere. These microbes showed\nthe greatest degrading potential at the biofilm maturation stage and\nexecuted the functions by PLA_depolymerase, polyesterase, hydrolase,\nand esterase. These findings will enhance understanding of BPs’\nenvironmental behavior and microbial roles on plastic degradation.