Abstract
The design of multiscale strategies integrating in vitro and in vivo models is necessary for the selection of new probiotics. In this regard, we developed a screening assay based on the investigation of the potential of yeasts from cheese as probiotics against the pathogen Salmonella Typhimurium UPsm1 (ST). Two yeasts isolated from raw-milk cheese (Saccharomyces cerevisiae 16, Sc16; Debaryomyces hansenii 25, Dh25), as well as S. cerevisiae subspecies boulardii (CNCM I-1079, Sb1079), were tested against ST by applying in vitro and in vivo tests. Adherence measurements to Caco-2 and HT29-MTX intestinal cells indicated that the two tested cheese yeasts presented a better adhesion than the probiotic Sb1079 as the control strain. Further, the Dh25 was the cheese yeast most likely to survive in the gastrointestinal tract. What is more, the modulation of the TransEpithelial Electrical Resistance (TEER) of differentiated Caco-2 cell monolayers showed the ability of Dh25 to delay the deleterious effects of ST. The influence of microorganisms on the in vivo model Caenorhabditis elegans was evaluated by measuring the longevity of the worm. This in vivo approach revealed that this yeast increased the worm’s lifespan and protected it against ST infection, confirming that this in vivo model can be useful for screening probiotic cheese yeasts.
Highlights
The gut microbiota is dominated by bacteria, but eukaryotic microorganisms contribute to the human microbiome [1,2]
Typhimurium was aerobically grown at 37 ◦C for 24 h in 50 mL Brain–Heart Infusion (BHI) broth (Biokar Diagnostics, Pantin, France), and yeasts were aerobically grown at 25 ◦C for 48 h, in 50 mL Yeast Extract–Peptone–Glucose (YPG) broth, at pH = 5.2 (40 g/L glucose (Sigma-Aldrich, St-Louis, USA), 5 g/L yeast extract (Biokar Diagnostics) and 5 g/L peptone (CONDA pronadisa, Madrid, Spain))
The ability to survive at pH 2.5 for 45 and 90 min, or a bile concentration of 3%, was the first step to determine the probiotic potential of the selected isolates of the following species: D. hansenii, S. cerevisiae, Y. lipolytica, and K. lactis from cheese
Summary
The gut microbiota is dominated by bacteria, but eukaryotic microorganisms contribute to the human microbiome [1,2]. Little is known about the interaction between non-Saccharomyces yeasts and the human microbiota, but other yeast species have been reported to have potential probiotic properties, including Debaryomyces hansenii, Kluyveromyces lactis, Yarrrowia lipolytica, and Issatchenkia occidentalis [10,11,12]. These species are frequently associated with dairy products such as raw-milk cheeses [13,14]. These facts could support and help the applications for human use
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