Twenty-three Lactobacillus strains of dairy origin were evaluated for some functional properties relevant to their use as probiotics. A preliminary subtractive screening based on the abilities to inhibit the growth of microbial pathogens and hydrolyze conjugated bile salts was applied, and six strains were selected for further characterization including survival under gastrointestinal environmental conditions, adhesion to gut epithelial tissue, enzymatic activity, and some safety properties. All selected strains maintained elevated cell numbers under conditions simulating passage through the human gastrointestinal tract, well comparable to the values obtained for the probiotic strain Lactobacillus rhamnosus GG, and were able to adhere to Caco-2 cells to various extents (from 3 to 20%). All strains exhibited high aminopeptidase, and absent or very low proteolytic and strong β-galactosidase activities; none was found to be haemolytic or to produce biogenic amines and all were susceptible to tetracycline, chloramphenicol, erythromycin, ampicillin, and amoxicillin/clavulanic acid. Our results indicate that the Lactobacillus strains analyzed could be considered appropriate probiotic candidates, due to resistance to GIT simulated conditions, antimicrobial activity, adhesion to Caco-2 cell-line, and absence of undesirable properties. They could be used as adjunct cultures for contributing to the quality and health related functional properties of dairy products.

The purpose of this study was to assess the chemical and microbial characteristics of 12 batches of artisanal Fiore Sardo, a protected designation of origin (PDO) hard cheese made from raw ewe's milk without addition of starters, during maturation. High standard deviations were observed for moisture percentage, total solids percentage and NaCl percentage content, possibly owing to differences in manufacturing processes and/or milk composition. Total mesophilic bacteria varied between 10 log10 cfu/g in 48‐h‐old cheese samples and 3 log10 cfu/g in 9‐month‐old samples. Total coliforms and staphylococci showed the highest counts at 48 h of ripening then decreased significantly, dropping to levels below 2 log10 cfu/g at 3 months of maturation. Lactic acid bacteria and enterococci were the dominant micro‐organisms throughout maturation. They were mainly represented by the species Lactococcus lactis ssp. lactis, Enterococcus faecium, Lactobacillus plantarum and Lactobacillus casei group. Low levels of yeasts were detected throughout the maturation period of the cheese. Debaryomyces hansenii and Kluyveromyces lactis var. lactis were the prevalent yeast species isolated.

In this work, six Kluyveromyces strains isolated from artisanal Fiore Sardo cheese were evaluated for some functional properties relevant to their use as probiotics. All strains were able to grow in the presence of conjugated bile salts after 72 h of incubation, and four were able to hydrolyse both sodium glycodeoxycholate and taurodeoxycholate. All strains survived well under simulated gastric conditions (pH 3.0), but Kl. marxianus strains presented the best survival rates values (83–100%) after exposure to artificial duodenum juice. Autoaggregation ability showed a certain variability with mean values ranging between 39.1 and 59.2%, while the hydrophobicity index was higher than 50% in five strains. All strains were able to adhere to Caco-2 cells (values ranging from 4 to 68%), with two Kl. lactis strains exhibiting significantly higher percentage adhesion than S. boulardii Codex used as control (P < 0.05). Kl. lactis strains also showed the broadest inhibitory range against pathogens. Finally, all strains were non-hemolytic and sensitive to the antimycotic agents tested. In conclusion, our results indicate that Kluyveromyces strains isolated from artisanal cheese possess interesting functional traits and absence of undesirable properties, and could be considered appropriate probiotic candidates

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