Engineering PET surface colonization with a synthetic bacterial consortium.

INTRODUCTION: Polyethylene terephthalate (PET) is a widely used synthetic polymer that persists in the environment because of its resistance to biological degradation. Although engineered PET hydrolases have shown improved catalytic performance, translating these advances into effective whole-cell degradation remains challenging because cells and enzymes must interact with an insoluble polymer surface.

METHODS: We developed a synthetic bacterial consortium to investigate early PET surface colonization and biofilm formation. The system combined Escherichia coli Nissle 1917 engineered for PETase expression with a biofilm-forming Pseudomonas putida strain evolved for growth on ethylene glycol. PET film incubation experiments, microscopy, biofilm quantification, and surface characterization were used to evaluate how extracellular enzyme targeting, consortium composition, and PET surface roughness influence microbial attachment.

RESULTS: Co-culture experiments with PET films showed that surface attachment was strongly influenced by extracellular enzyme targeting and consortium composition. The strongest and most persistent attachment was observed when extracellular enzyme availability was paired with the biofilm-forming partner. Quantitative analysis showed an approximately 1.5-fold increase in biofilm formation in the engineered consortium relative to the control. In addition, mechanical roughening of PET surfaces further increased biofilm formation, indicating that surface accessibility is an important determinant of microbial attachment.

DISCUSSION: Our findings show that PETase secretion, consortium composition, and polymer surface roughness may collectively influence biofilm formation on PET and could therefore be considered when designing future whole-cell PET bioprocessing systems.