Emmental cheese environment enhances Propionibacterium freudenreichii stress tolerance
Jardin, Julien | Rabah, Houem | Briard-Bion, Valérie | Jan, Gwénaël
Dairy propionibacteria are actinomycetales found in various fermented food products. The main species,Propionibacterium freudenreichii , is generally recognized as safe and used both as probiotic and as cheese starter. Its probiotic efficacy tightly depends on its tolerance towards digestive stresses, which can be largely modulated by the ingested delivery vehicle.Indeed, tolerance of this bacterium is enhanced when it is consumed within a fermented dairy product, compared to a dried probiotic preparation. We investigated both stress toler-ance and protein neosynthesis upon growth in i) chemically defined or ii) aqueous phase of Emmental cheeses. Although the same final population level was reached in both media, a slower growth and an enhanced survival of CIRM BIA 1 strain of P. freudenreichii subsp. shermanii was observed in Emmental juice, compared to chemically defined medium. This was accompanied by differences in substrates used and products released as well as over-expression of various early stress adaptation proteins in Emmental juice, compared to chem-ically defined medium, implied in protein folding, in aspartate catabolism, in biosynthesis ofvaline, leucine and isoleucine, in pyruvate metabolism in citrate cycle, in the propionate metabolism, as well as in oxidoreductases. All these changes led to a higher digestive stress tolerance after growth in Emmental juice. Mechanisms of stress adaptation were induced in this environment, in accordance with enhanced survival. This opens perspectives for the useof hard and semi-hard cheeses as delivery vehicle for probiotics with enhanced efficacy
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