Acid stress susceptibility and acid adaptation of Propionibacterium freudenreichii subsp. shermanii

Free access article

Issue		Lait Volume 80, Number 3, May-June 2000


Page(s)		325 - 336
DOI		http://dx.doi.org/10.1051/lait:2000128

DOI: 10.1051/lait:2000128

Lait 80 (2000) 325-336

Acid stress susceptibility and acid adaptation of Propionibacterium freudenreichii subsp. shermanii

Gwénaël Jan - Annette Rouault - Jean-Louis Maubois

Laboratoire de Recherches de Technologie Laitière, INRA, 65 rue de Saint-Brieuc, 35042 Rennes Cedex, France

(Received 25 October 1999; accepted 28 December 1999)

Abstract:

The probiotic application of dairy propionibacteria as well as their use in cheese technology implies exposure to various environmental stresses, including acidic pH. The acid tolerance response (ATR) of Propionibacterium freudenreichii was investigated. One strain present in Swiss-type cheese proved to be acid-tolerant, since no lethal effect was observed during exposure at pH 3. Moreover, survival at pH 2 (acid challenge) was conferred by pre-exposure to a moderate acid stress (acid adaptation). This adaptative response was triggered quickly, and showed a maximal efficiency upon exposure to pHs between 4 and 5. Stationary phase ATR and acid habituation were also demonstrated, and conferred increased survival at pH 2 without pre-exposure. Exponentially-growing bacteria were partially protected towards acidity by pre-exposure to other stresses (heat, starvation, but not hyperosmolarity). A comparative study of different strains revealed that acid stress susceptibility is strain-dependent within this species. Adaptation and survival at low pH is likely to determine the efficacy of a P. freudenreichii strain both as a cheese starter and as a probiotic.

Keywords: Swiss-type cheese / Propionibacterium / acid tolerance response / stress / probiotic

Résumé:

Sensibilité et adaptation vis-à-vis du stress acide chez Propionibacterium freudenreichii subsp. shermanii. L'application probiotique des bactéries propioniques laitières, de même que leur utilisation en technologie fromagère, entraîne leur exposition à divers stress environnementaux, dont le stress acide. Nous avons étudié l'acquisition de tolérance en réponse au stress acide (ATR) chez Propionibacterium freudenreichii. Une souche présente dans un fromage à pâte pressée cuite s'est révélée tolérante, puisque aucun effet létal n'a été observé pendant une exposition à un pH de 3. De plus, la pré-exposition à un pH modérément acide (adaptation) a permis la survie à pH 2 (épreuve). Cette réponse adaptative est déclenchée rapidement et présente un optimum d'efficacité entre pH 4 et 5. L'ATR de phase stationnaire ainsi que l'habituation à l'acidité ont également été démontrées et améliorent la survie à pH 2 sans pré-traitement. Les bactéries récoltées en phase exponentielle de croissance sont partiellement protégées de l'épreuve acide par pré-exposition à d'autres stress (chaleur, carence nutritive, mais pas le stress hyperosmotique). Une étude comparative de différentes souches a révélé que la susceptibilité au stress acide dépendait de la souche au sein de cette espèce. L'adaptation et la survie à bas pH déterminent probablement l'efficacité de P. freudenreichii à la fois en tant que levain et en tant que probiotique.

Mots clé : Emmental / Propionibacterium / adaptation / stress acide / probiotique

Correspondence and reprints: Gwénaël Jan
Tel.: (33) 2 23 48 21 47; fax: (33) 2 23 48 53 50; e-mail: gjan@labtechno.roazhon.inra.fr

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