Fungal biodiversity in commercial table olive packages

In this work, a metataxonomic analysis of the ITS region has been carried out over a total of 72 commercial table olive packages obtained around the world to elucidate the fungal biodiversity related to them. Viable counts in selective yeast/mold media ranged from not detected in the 25% of cases (<1.6 log10 CFU/g) to a maximum of 5.86 log10 CFU/g. Only 4.16% of samples did not pass the quality control necessary for the metataxonomic analysis, which revealed that almost half of the total of sequences obtained from all packages corresponded to the Pichia genus (44.08%), followed by Citeromyces (14.45%), Candida (8.07%), and Wickerhamomyces (6.95%). In lower proportions were also detected other genera such as Starmerella (3.60%), Saccharomyces (2.24%), Debaryomyces (2.08%), and Dekkera (2.05%). The statistical analysis allowed to relate the presence of certain fungi taxa as a function of the type of elaboration (lye treated, green, and black natural olives), presentation (pitted, whole, or sliced samples), and packaging material/system (glass, PET, plastic bags, and vacuum). Zygotorulaspora genus was especially sensitive to the presence of potassium sorbate, while other genera such as Sporobolomyces, Moniliella, and Gibellulopsis were more abundant in packages treated with this preservative. Lastly, potential fungi pathogens genera such as Alternaria, Kodamaea, Lodderomyces, Malasessia, or Aspergillus were detected in low proportions (>0.3%), although with higher representation in some individual samples. Our results contribute to improving the knowledge of the fungal population in this ready-to-eat fermented vegetable, providing us a strong tool to assess the safety, stability, and quality of the final product.