Cheese matrix protects the immunomodulatory surface protein SlpB of Propionibacterium freudenreichii during in vitro digestion
Résumé
Propionibacterium freudenreichii is a traditional Swiss-type cheeses starter and constitutes an emergent probiotic,
exerting several beneficial effects, including anti-inflammatory modulation of gut inflammation. This feature
relies on several metabolites and on surface proteins, with a prominent role of the surface protein SlpB. In this
study, we firstly investigated the relevance to avoid SlpB digestive proteolysis, by comparing the effect of i) P.
freudenreichii CIRM-BIA 129, ii) its native Slps, or iii) peptides resulting from Slps digestive proteolysis, with
respect to modulation of HT-29 cells response to a lipopolysaccharide (LPS) challenge. The anti-inflammatory
effect exerted by P. freudenreichii CIRM-BIA 129 and by its native surface proteins (Slps) on HT-29 cells was
abolished by digestive proteolysis. This result confirmed the importance to protect immunomodulatory surface
proteins from digestive proteolysis in order to allow gut immune system modulation. Thus, we examined the
effect of dairy matrices on P. freudenreichii viability and on SlpB integrity during digestion. In comparison with
liquid matrices, the cheese matrix provided an enhanced tolerance towards digestive stresses and protection of
SlpB towards proteolysis, during two in vitro digestion models: static and dynamic. Taken together, these results
show that cheese is an adequate delivery vehicle for P. freudenreichii immunomodulatory proteins. This opens
perspectives for the development of fermented dairy functional foods aimed at target populations at high risk for
diet-related diseases with an inflammatory component.