Bioprospecting hidden yeasts in artisanal dairies: Revealing potential probiotics for functional fresh cheese

Artisanal dairies represent a significant reservoir of microbial biodiversity, offering unique opportunities to discover novel strains with functional properties. This study aimed to isolate and characterize wild yeast strains from traditional sheep cheese production in Central Italy evaluating their probiotic potential and technological suitability for fresh cheese manufacturing. Twenty-five wild yeast strains, belonging to Candida friedrichii, Candida zeylanoydes, Debaryomyces hansenii, Metschnikowia spp., Kluyveromyces lactis, and Yarrowia lipolytica, were screened for technological traits, including survival in milk, acidification activity, lactose consumption, and salt tolerance. Results identified four promising strains-C. zeylanoydes DiSVA 1132, D. hansenii DiSVA 1156, Metschnikowia spp. F14, and K. lactis DiSVA 1209-which demonstrated high viability under the tested milk-incubation conditions, reaching more than 10⁶-10⁷ CFU/mL in line with the commonly discussed target levels for potential probiotic foods, and significant acidifying capacity (pH reduction to ∼4.5). These strains were used as a microbial consortium in co-fermentation with a commercial Lactobacillus casei strain to produce a functional fresh cheese, following the Squacquerone di Romagna DOP specifications. The yeast pool did not negatively affect the growth of the bacterial starter and significantly enhanced sensory characteristics and preliminary functional-food potential. Sensory analysis confirmed that the yeast consortium improved the perception of texture, consistency, and overall aroma of the final product. These findings highlight the potential of using autochthonous "next-generation" probiotic yeasts to develop innovative functional dairy products with enhanced sensory and technological suitability properties.