SOFRALIK YEŞİL ZETİN FERMENTASYONUNDA NON- SACCHAROMYCES MAYALARIN STARTER KÜLTÜR POTANSİYELİNİN MOLEKÜLER YÖNTEMLERLE DEĞERLENDİRİLMESİ

Olives have been an essential component of the Mediterranean diet for centuries. However, olives are naturally inedible due to phenolic compounds, particularly oleuropein, which impart bitter taste. Oleuropein degradation is necessary to make them suitable for consumption. This study evaluated the potential of indigenous non-Saccharomyces yeasts as a starter culture for green table olive fermentation, focusing on their ability to degrade oleuropein as an alternative to spontaneous fermentation and alkaline treatment. Three yeast species -Metschnikowia pulcherrima, Wickerhamomyces anomalus and Hanseniaspora opuntiae- were selected as starter culture candidates based on their biotechnological properties and inoculated to green table olive fermentations. Whole genome sequencing of selected yeasts and amplicon-based sequencing of brine samples were carried out using Oxford Nanopore Technology. Yeast inoculated fermentations were compared with spontaneous fermentation and alkaline treatment across multiple aspects. Amplicon-based sequencing and qPCR results indicated that selected yeasts became dominant within the fungal community while bacterial community was not substantially affected. Moreover W. anomalus, M. pulcherrima, Saccharomyces cerevisiae, Hanseniaspora spp. were detected as part of the native microbiota of Sarı ulak cultivar. Oleuropein levels were significantly lower in yeast inoculated fermentations, particularly H. opuntiae inoculated trial, than the spontaneous fermentation. Finally, selected yeasts were identified at the genome level and in silico annotation of whole genome sequencing revealed predicted proteins associated with food safety, β-glucosidase and killer toxin associated proteins. Overall, findings of this study indicate that selected indigenous yeasts are promising starter candidates and may have the potential alternative approach to spontaneous fermentation and alkaline treatment.