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Saccharomyces cerevisiae is a sustainable yeast with many applications in the food industry. Here, we study the use of a Saccharomyces cerevisiae model composed of three different industrial strains (a wine, a beer and a baker's strain) to assess the antifungal activity of three organic plant-based extracts (Hypericum perforatum 10% w/w, Pistacia lentiscus var. Chia 20% w/w and Rosmarinus officinalis 6% w/w). Three different methods were employed (agar disc diffusion, spot assay, and growth curve analysis). Only the Rosmarinus officinalis extract (6% w/w) exhibited inhibitory activity against all the tested yeast strains in the agar disc diffusion method. In the spot assay, all extracts and their carrier oils (sunflower oil and caprylic triglyceride) exerted similar mild antifungal activity. In the growth curve analysis, all extracts significantly lowered the growth rate of the yeasts, but this was not observed for the carrier oils. The results highlighted that it is important to consider more than one method for testing the antimicrobial activity of different compounds. The three yeast strains exhibited differences in their susceptibility to pharmaceutical antifungals, and the beer and baker's yeasts were resistant to itraconazole. Moreover, polyphenols were detected in all natural extracts which may be linked to their antifungal activity. Our results suggest that we might consider multiple use of these natural extracts in the food industry as food additives or even preservatives to delay food spoilage. [ABSTRACT FROM AUTHOR]

Fermented foods such as table olives are produced through a spontaneous process that has been improved over the years, ensuring the safety and quality of the final product. The aim of the present work was to study the action of starter cultures of lactic acid bacteria (Lacticaseibacillus rhamnosus GG ATCC53103, Levilactobacillus brevis ATCC8287, and Lactiplantibacillus plantarum ATCC14917) which were previously shown to have probiotic and antioxidant potential during the fermentation of natural Greek-style black olives (Kalamata) in brine containing 6% (w/v) NaCl at a temperature of 20 °C for a period of 150 days. At a molecular level, the main metabolites in every fermentation process were identified using an HPLC method. The results showed that the concentration of the metabolites increased gradually, developing a stable pattern after the 90th day of fermentation. In addition, the DL-p-hydroxyphenyllactic acid (OH-PLA) was identified as the phenolic acid with the highest concentration, independently of the selected starter culture. Microbial genomic DNA was also extracted from the olives' surface at the final stages of fermentation (150 days) and was subjected to 16S rRNA sequencing using the Nanopore MinION™ NGS tool, enabling a comprehensive analysis of the microbial community. According to the findings, the most abundant genera were Lactobacillus and Leuconostoc. To the best of our knowledge, this is the first study exploring these particular starters for olive fermentation. [ABSTRACT FROM AUTHOR]