Plastic is used worldwide due to its versatile properties, but it becomes a big problem when we discard it. The degradation of plastics is very slow, so more and more plastic is polluting our planet. When it comes to global plastic pollution, the solution may lie in various microorganisms that can help us degrade plastic. Currently, this strategy is hardly used, but the identification of plastic-degrading microorganisms is the subject of intensive research. Such microorganisms can be found in extreme environments, for example salterns. Many extreme microorganisms secrete various enzymes to degrade complex polymers and many of them are active at low water activity. This property is important for the degradation of plastic, which pollutes the oceans in large quantities. In this work, we attempted to identify halotolerant fungi from salterns that degrade plastics and to determine the effect of added salt on plastic degradation. We tested 60 halotolerant fungal strains from Sečovlje salterns and evaluated them for their ability to biodegrade polyamide, polyethylene, polyethylene terephthalate, polypropylene, and polyurethane. First, we determined the lowest and the highest salt concentration at which fungi can grow. Then we cultivated them in liquid medium with plastic as the sole carbon source. We monitored the degradation of plastic by measuring the concentration of released carbon dioxide (CO2) during the fungal growth using gas chromatography. From the 60 fungal strains tested, we identified five candidate strains (Penicillium brevicompactum, Alternaria arborescens, Eurotium amstelodami, Penicillium fundyense in Phaeotheca triangularis) that show signs of plastic degradation in the absence of salt, and three strains (Aspergillus silvaticus, Aspergillus restrictus in Aspergillus pseudoglaucus) that show signs of degradation in the presence of salt.
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