Extremotolerant fungi have great biotechnological potential, but some are also opportunistic human pathogens. In this work, we investigated the potential of their use in biocontrol and biodegradation of plastics and evaluated how safe their use is. We found that strains of the Arctic black yeast Aureobasidium subglaciale are at least as good or even better for biocontrol than the commercial biocontrol strains Aureobasidium pullulans. We have isolated and characterized the extracellular vesicles (EVs) from the fungus A. pullulans and found that they cause some changes in the morphology of the phytopathogenic fungi Penicillium expansum and Colletotrichum acutatum. Neither A. pullulans nor A. subglaciale grow at 37 °C, so they can be used safely, which is not the case for Aureobasidium melanogenum. The latter also has other virulence factors (e.g., synthesis of siderophores and hemolytic activity), which were confirmed by phenotypic and genomic analyzes of dozens of strains of this species. We isolated EVs from A. melanogenum and prepared a fraction with and a fraction without melanin and showed that neither fraction had a cytotoxic effect on cells of the SH-SY5Y cell line. By testing different fungal species, we found that the species Coniochaeta hoffmannii and Pleurostoma richardsiae partially degraded polypropylene (PP), especially when it was previously subjected to photocatalysis, which was confirmed by Raman spectroscopy and FTIR-ATR. The properties that make such extremotolerant fungi interesting for biotechnology often overlap with those used in pathogenesis. By characterizing the properties of extremotolerant fungi, we can effectively identify the best strains for biocontrol and plastic degradation while identifying and excluding potential opportunistic pathogens from biotechnological use.
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