SURFING: Starter SURFace against INflammation of the Gut: any unrevealed probiotic potential in dairy starters?

Cheeses and other fermented dairy products constitute a tremendous source of live and active bacteria in our diet. Depending on the product, on the strain and on the health status of individuals, this major bacterial intake can have beneficial effects, or not! Recognized molecular, cellular and animal models have been developed to detect and study probiotic bacterial strains. These tools may also reveal unexpected probiotic potential in bacterial strains within the tremendous biodiversity present in traditional fermented products. In our team, we focused on dairy propionibacteria, taking advantage of a unique biological resource center. We hypothesized that strains considered for techno-functional reasons (aroma, texture), may also play a beneficial role in the context of Inflammatory Bowel Diseases (IBD).Propionibacterium freudenreichii is a beneficial bacterium used in the food industry as a vitamin producer, as a bio-preservative and as a cheese ripening starter. Some strains are known to adhere to intestinal epithelial cells and mucus and to modulate important functions of the gut mucosa, including cell proliferation and immune response. Selected strains show promising immunomodulatory properties with an anti-inflammatory protective evidenced effect in vitro and in vivo. Adhesion of probiotics and cross-talk with the host rely on the presence of key surface proteins, still poorly identified. Identification of the determinants of adhesion and of immunomodulation by P. freudenreichii remains a bottleneck in the elucidation of its probiotic properties.During 3 years, a national research project funded by ANR (Agence Nationale de la Recherche) investigated statistical links between immunomodulatory properties of 23 P. freudenreichii strains and their cellular proteins using comparative genomics, transcriptomics and proteomics. In particular, three complementary proteomic methods were used to identify key surface-exposed proteins involved in probiotic effects. We then developed experimental monoxenic fermented dairy products, exclusively fermented by an anti-inflammatory selected strain of P. freudenreichii. Key surface proteins, involved in its immunomodulatory effects, were expressed within these products. Their consumption exerted an anti-inflammatory effect in vivo.This work reveals an unexpected probiotic potential in industrial dairy propionibacteria starters. It opens exciting perspectives in a context of growing occurrence of IBD, multifactor diseases related to diet, and provides a new functional fermented product for preclinical and clinical studies aimed at prevention or treatment of IBD.