Cheese matrix protects the immunomodulatory surface protein SlpB of Propionibacterium freudenreichii during in vitro digestion

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 featurerelies on several metabolites and on surface proteins, with a prominent role of the surface protein SlpB. In thisstudy, 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, withrespect to modulation of HT-29 cells response to a lipopolysaccharide (LPS) challenge. The anti-inflammatoryeffect exerted by P. freudenreichii CIRM-BIA 129 and by its native surface proteins (Slps) on HT-29 cells wasabolished by digestive proteolysis. This result confirmed the importance to protect immunomodulatory surfaceproteins from digestive proteolysis in order to allow gut immune system modulation. Thus, we examined theeffect of dairy matrices on P. freudenreichii viability and on SlpB integrity during digestion. In comparison withliquid matrices, the cheese matrix provided an enhanced tolerance towards digestive stresses and protection ofSlpB towards proteolysis, during two in vitro digestion models: static and dynamic. Taken together, these resultsshow that cheese is an adequate delivery vehicle for P. freudenreichii immunomodulatory proteins. This opensperspectives for the development of fermented dairy functional foods aimed at target populations at high risk fordiet-related diseases with an inflammatory component