Biodiversity and enzymatic activities of fungal communities in Italian oleic ecosystems

Olive oil and its by-products are ecological niches for various yeast and filamentous fungi, and their occurrence can significantly influence olive oil quality. Fungal esterase- lipase enzymes can negatively affect it by increasing free fatty acids and favouring auto- oxidation. Concurrently, β-glucosidase positively contributes to it by reducing bitterness by breaking down phenolic compounds. This study aimed to isolate and identify fungal species from olive oil and by-products and evaluate the principal enzymatic activities of fungal isolates associated with olive oil quality. Olives, olive oil, pomace, and paste samples were collected from three production areas in Verona (Italy). Yeasts and filamentous fungi were isolated, identified and screened for esterase-lipase and β-glucosidase activities. Those found to be positive were further analyzed quantitatively. A total of 66 yeast isolates and 10 filamentous fungi, belonging to 22 and 7 species, respectively, were identified. The screening revealed that 25 yeast and 10 fungal isolates exhibited significant enzymatic activities. In the quantitative analysis, the esterase-lipase activity was especially prominent in strains of F. magnum, G. candidum, and R. graminis. Nakazawea. molendinolei OVI2 exhibited the highest β-glucosidase activity. Among filamentous fungi, P. brevicompactum and C. perangustum strains showed notable β- glucosidase activity, while esterase-lipase activity was marked in isolates of C. allicinum, C. perangustum, and P. brevicompactum. This study provided additional insights into the fungal community inhabiting oleic ecosystems and their enzymatic activities involved in olive oil quality. Further studies are necessary to evaluate their specific impact on the quality of olive oil during the storage.