Preliminary study by molecular methods on yeast population of differently fermented green table olives of the cultivar Nocellara messinese

Introduction: Main microorganisms involved in table olive fermentations are lactic acid bacteria and yeasts. During fermentation the presence and the dominance of microorganisms are affected by factors such as pH and salt concentration. Aim of the present study was to investigate the yeast population in fermentations with brine at different concentration of NaCl, also artificially acidified. Materials and Methods: Vats containing olives of Nocellara messinese cultivar were filled with brines formulated as follow: a) 8% NaCl (w/v), b) 8% NaCl acidified to pH 4.3, c) 5% NaCl for 20 days and then brought to 8% NaCl, d) 5% NaCl for 20 days, then brought to 8% NaCl and acidified to pH 4.3. Fermentations were carried out at room temperature for 8 months. Yeasts were isolated on YPD medium throughout the fermentation time. The yeast identifications were performed by PCR-RFLP of the internal transcribed spacer region; DNA was extracted from the different olive trials. Results and Discussion: A total of 100 yeasts was isolated; they belong mainly to the species Kluyveromyces marxianus, Pichia kudriavzevii, and Wycherhamomyces anomalus. These species were confirmed by culture-independent method that allowed tracing the yeast population. Throughout the 8 months, different evolution of the yeast population was observed; this is mainly related to the technological parameters used in the fermentations. The main yeast technological traits will be studied; the correlation between the yeast population and the brine formulation will be useful to improve the quality and the shelf life of the fermented olives.