Development of autochthonous yeast starter cultures for Taggiasca table olives: Microbial ecology and metabolomic profile under standard and reduced-salt fermentation conditions.

Taggiasca table olives are a native variety to Liguria (Italy) that undergo spontaneous fermentation in a traditional manner. The autochthonous microbiota of Taggiasca olives is typically dominated by yeasts, while lactic acid bacteria are often unable to compete probably due the high phenolic content of this variety. Consequently, the fermentation kinetics and metabolomic profile are determined primarily by indigenous yeasts. This study evaluated three autochthonous yeast starter cultures for Taggiasca fermentation under standard (10% w/v) and low (6% w/v) salt conditions. Three yeast strains (Pichia membranifaciens TUCC00000520, Candida diddensiae TUCC00000529, and Wickerhamomyces anomalus TUCC00000536), previously isolated from Taggiasca fermentations, were inoculated in different formulations. Dynamics of the microbial community were monitored with an integrated approach, using culture-dependent (plate counts, MALDI-TOF MS, and RAPD-PCR) and culture-independent methods (metataxonomics approach). The metabolome was characterized at the final stage of fermentation via organic acid determination, 1H NMR and untargeted volatile organic compounds (VOCs) analysis. Results highlighted an influence of the selected yeasts on the microbial dynamics and metabolomic profile of the final product with P. membranifaciens TUCC00000520 isolated until late stages of fermentation. Overall, this study validates the feasibility of autochthonous yeast-driven, cultivar-specific starters and provides a strategic framework for optimizing Taggiasca olive fermentation.