Priestia megaterium Jou-S14 degrades highly crystalline polyethylene terephthalate microplastics

In natural environments, the crystallinity of PET bottles and microplastics exceeds the degradation capacity of known enzymes, making untreated PET with crystallinity above 10% present a significant challenge for direct enzymatic biodegradation. In this study, Priestia megaterium Jou-S14, isolated from coastal environments in Jiangsu Province, efficiently degraded highly crystalline polyethylene terephthalate microplastics (hcPET-MPs). After 30 days, strain Jou-S14 caused weight losses of 5.02 ± 0.21% for hcPET-MPs and 7.09 ± 0.35% for hcPET films. Degradation assessments revealed that strain Jou-S14 rapidly colonized the surface of hcPET-MPs, disrupted crystalline regions, and produced BHET and TPA. Furthermore, genomic analysis identified an IsPETase-type PET hydrolase, PmPETase (GenBank No.: PX379572.1), featuring the catalytic triad Ser¹⁵¹-Asp²²²-His²⁵³, which formed a stable hydrogen-bonding network with the substrate BHET. Purified PmPETase was active at pH 8.0 and 35 ℃, producing BHET (1.75 μM) and TPA (8.49 μM) from hcPET-MPs within 24 h. We proposed a pathway in which strain Jou-S14 channels the hydrolysis products of hcPET-MPs into central metabolism. This study expands the available marine PET-degrading microbial resource repository and supports strategies for microbial consortia-assisted recycling of highly crystalline PET.