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This work examines the formation of poly-microbial communities adhered to the epidermis of natural green Gordal olives and the application of different methodologies for recovery and counting of the microorganisms embedded in olive biofilms. The fermentation process was physicochemical and microbiologically monitored for 90 days, at which, formation of true biofilms on the skin of fermented fruits was confirmed by scanning electron microscopy. Then, samples of olives were taken and treated with sonication, enzymes, mechanical homogenization with stomacher and ultrasonic bath for biofilm disaggregation. The use of the stomacher for 1 min was the most effective treatment to release the lactic acid bacteria (6.6 log10 cfu g(-1)), whereas sonication for 5 min was the most efficient method for quantification of yeasts (up to 3.5 log10 cfu g(-1)). Molecular identification of isolates obtained from natural Gordal olive biofilms revealed that Lactobacillus pentosus was the only species found among lactic acid bacteria, while Pichia membranifaciens was the dominant yeast species, with higher counts obtained for the bacteria.

This study delved into the evolution of fungal population during the fermentation of Spanish-style green table olives (Manzanilla cultivar), determining the influence of different factors such as fermentation matrix (brine or fruit) or the use of a lactic acid bacteria inoculum, on its distribution. The samples (n = 24) were directly obtained from industrial fermentation vessels with approximately 10.000 kg of fruits and 6.000 L of brines. Our findings showcased a synchronized uptick in lactic acid bacteria counts alongside fungi proliferation. Metataxonomic analysis of the Internal Transcribed Spacer (ITS) region unearthed noteworthy disparities across different fermentation time points (0, 24, and 83 days). Statistical analysis pinpointed two Amplicon Sequence Variants (ASV), Candida and Aureobasidium, as accountable for the observed variances among the different fermentation time samples. Notably, Candida exhibited a marked increase during 83 days of fermentation, opposite to Aureobasidium , which demonstrated a decline. Fungal biodiversity was slightly higher in brines than in fruits, whilst no effect of inoculation was noticed. At the onset of fermentation, prominently detected genera were also Mycosphaerella (19.82 %) and Apohysomyces (16.31 %), hitherto unreported in the context of table olive processing. However, their prevalence dwindled to nearly negligible levels from 24th day fermentation onwards (<2 %). On the contrary, they were replaced by the fermentative yeasts Saccharomyces and Isstachenkia. Results obtained in this work will be useful for designing new strategies for better control of table olive fermentations. • Metataxonomic analysis of ITS region was applied in Spanish-style olive fermentations. • Variances in yeast population were detected at 0, 24, and 83 days of fermentation. • Candida and Aureobasidium were the responsible genera for the statistical differences • No significant differences were observed in fermentation matrix or inoculation process. [ABSTRACT FROM AUTHOR]

This work focuses on the persistence of the putative probiotic bacteria Lactobacillus pentosus TOMC- LAB2 on green Spanish-style Manzanilla olives according to different packaging conditions and storage temperatures. The lactic acid bacteria population decreased with time but the highest survival counts (and lowest yeasts) at the end of storage (8 months) were observed in plastic pouches under nitrogen atmosphere and glass jars with brine stored at 20°C. Molecular techniques showed a 100% presence of the putative probiotic bacteria in biofilms adhered to olive epidermis, while it was absent in PPB (plastic pouches with brine) and in olives stored at 7°C. No changes in NaCl, pH or combined acidity were observed during the storage except for a slight increase in titratable acidity at 20°C. The color of the fruits was stable but degraded at 20°C for olives in plastic pouches with brine. [ABSTRACT FROM AUTHOR]

In this work, a total of 72 commercial table olive packages obtained from different international markets were analysed to determine their fungal biodiversity. Viable fungal counts ranged from the detection threshold (<1.6 log 10 CFU/g in 25% of cases) to a maximum of 5.86 log 10 CFU/g. Assignation of fungal taxonomy was carried out through a metataxonomic analysis of the ITS region, which revealed that almost half of the total 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 link certain taxa to specific types 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). Likewise, 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 pathogenic fungal 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 our knowledge of the fungal population associated with this ready-to-eat fermented vegetable, providing us a strong tool to assess the safety, stability, and quality of the final product. • Metataxonomic approach of ITS region was applied in global commercial olive packages. • Half of total sequences obtained from all packages corresponded to the Pichia genus. • Potential pathogenic fungi were detected in high representation in some samples. • The presence of certain fungal taxa was influenced by the packaging conditions. [ABSTRACT FROM AUTHOR]