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Biodegradation of weathered polystyrene (PS) and polypropylene (PP) microplastics after exposure to marine microorganisms

Lazaridi Paraskevoula

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Year 2020
Type of Item Diploma Work
Bibliographic Citation Paraskevoula Lazaridi, "« Biodegradation of weathered polystyrene (PS) and polypropylene (PP) microplastics after exposure to marine microorganisms»", Diploma Work, School of Environmental Engineering, Technical University of Crete, Chania, Greece, 2020
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Plastic waste ends up in marine and coastal environment, with increased rate. Although marine pollution from plastics has been the target of many studies, there are still many gaps in understanding the concentrations, characteristics and impacts of plastics on marine ecosystems. In the marine environment, plastics as well as plastic floating on the surface of the sea are colonized by various microbial species. The ability of marine micro-organisms to biodegrade polymers using the plastic as the sole carbon source is a relatively new research area. The most commonly used plastics are never completely removed but are dispersed in microplastics due to exposure to ultraviolet (UV) radiation, extreme temperatures, mechanical stress, waves, air and sand as well as biological activity. Plastic microspheres are one of the most common plastic debris found in the world's seas and shores.The aim of this diploma thesis is to study the impact of the microbial communities of the pelagic community of Souda on microspheres of polypropylene and polypropylene in a simulated marine environment, where microplastics are the only carbon source. The microspheres were initially irradiated (UV) to achieve aging of the plastics. Immediately the pelets were placed in a sterile conical flasks with sterile sea water and were inoculated with the marine microbial community. They were placed on a shaker for 5 months. Next, a series of microbial weight, microbial growth, protein and carbohydrates contect in biofilm, velocity speed, and microplastic size measurements were performed monthly to assess the effect of marine microorganisms on microspheres.Marine microorganisms have successfully developed and thrived in the simulated marine microcosm. A significant weight reduction was observed during the 5th month for polystyrene 1.99% and for polypropylene 9.65%. Additionally, increases in protein and carbohydrate concentrations were observed. Finally, a large percentage of nanoparticles were observed, at the 5th month for both microplastics species, and all of this indicates the successful biodegradation of microspheres by marine microorganisms.

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