Delineating degradation of polyethylene microplastics by mangrove-derived microbes: Enzymatic pathways and intermediate identification

The accumulation of polyethylene microplastics (PE-MPs) in marine and coastal environments, particularly mangrove ecosystems, poses significant environmental challenges. To address this, we investigated the bioremediation potential of two bacterial strains, Lysobacter sp. (MAS-1) and Nitratireductor kimnyeongensis (MAS-2), isolated from biofilm-coated PE-film in a Thailand mangrove area. Microbial community analysis revealed a shift toward Proteobacteria (47-92 %) and Actinomycetota (5-41 %) in PE-MP-enriched consortia, indicating niche specialization. Both strains exhibited significant degradation, with MAS-1 achieving 35.4 ± 1.2 % and MAS-2 achieving 23.04 ± 0.8 % weight loss of PE-MPs within 30-days. Biofilm assays confirmed substantial microbial adhesion on PE-MPs, and SEM imaging revealed surface pitting and cracking, indicative of microbial colonization and polymer breakdown. While FT-IR analyses showed oxidative modifications including carbonyl (CO), hydroxyl (-OH), and ether (C-O) groups, enhancing PE surface hydrophilicity. LC-MS/MS identified organic acids and nitrogen- and sulfur-rich compounds in a liquid medium, with in silico BioTransformer 3.0 analysis predicting strain-specific pathways like sulfur oxidation for MAS-1 and dehalogenation of MAS-2. These findings establish the bioremediation potential of mangrove-derived microbes and highlight the strains' distinct metabolic roles in PE-MP degradation.