Organic matter adsorbs onto microplastic surfaces, substantially affecting their physicochemical properties. In this master’s thesis, we investigated the effects of extracellular polymeric substances (EPS) derived from biofilms of Pseudomonas lundensis, a psychrotrophic bacterium associated with chicken meat spoilage, on the surface properties of microplastics prepared from polyethylene terephthalate-based food packaging foil. EPS was isolated using three methods: centrifugation (B), sodium carbonate treatment (C), and formaldehyde/NaOH treatment (F). The composition of the resulting EPS isolates was evaluated based on their polysaccharide, protein, and extracellular DNA contents. Microplastics were incubated in the EPS isolates, after which changes in their surface properties were assessed by contact angle measurements, X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The isolation method significantly affected the content of individual components in the EPS isolates. The presence of EPS residues on the microplastic surfaces increased the surface free energy, with statistically significant differences observed for EPS isolated using methods C and F. XPS and ToF-SIMS analyses further confirmed changes in the chemical composition of the microplastic surface. Overall, the results indicate that the effects of P. lundensis biofilm EPS on microplastic surface properties depend on its biochemical composition, and that EPS contributes to the formation of organic conditioning layers whose characteristics differ among individual EPS isolates.
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