Exploring the mechanism of low-density polyethylene depolymerization and extracellular electron transfer at bio-nano interfaces mediated by biofilm-forming electroactive bacteria.

The environmental persistence of low-density polyethylene (LDPE) results from its hydrophobic surface and inert C-C backbone, which restrict microbial colonization and oxidative chain breakdown. Although extracellular electron transfer (EET) is a defining feature of electroactive bacteria (EAB), its role in polyolefin oxidation remains understood. Here, we developed a hybrid bio-nano platform combining EAB from plastic-contaminated soils with Fe3O4-NPs to enhance LDPE biodegradation by integrating EET-associated redox activity, biofilm formation, and oxidative catalysis. The selected strains, Acinetobacter johnsonii PDB-22 and Pseudomonas aeruginosa PDB-38, exhibited biofilm-forming capacity (1.20 ± 0.13 and 0.98 ± 0.10, respectively) and electrochemical activity. The integration of Fe3O4-NPs accelerated the biodegradation, resulting in reductions in polymer weight (11.2 ± 1.2% and 10.5 ± 0.3%, respectively), crystallinity (32.8% and 24.7% relative reduction, respectively), tensile strength (55.0% and 38.8% reduction, respectively), and molecular weight (18.0% Mw reduction for PDB-22-NPs). Mechanistically, Fe3O4-NPs enhanced oxidative enzyme activities and altered their temporal catalytic behavior, consistent with more sustained ROS-associated oxidative depolymerization. Metabolomic profiling revealed strain-specific oxidative transformation patterns, consistent with differences in LDPE depolymerization. These findings support a functional contribution of EET-associated redox activity to LDPE oxidation at the bacteria-NP-polymer interface and provide a promising strategy for plastic bioremediation and a circular bioeconomy.