Survival of cheese-ripening microorganisms in a dynamic simulator of the gastrointestinal tract Nad  ege Adouard a, b , Laurent Magne b , Thomas Cattenoz b , Herv  e Guillemin b , Benoît Folign  e c , Daniel Picque b , Pascal Bonnarme b, * a AgroParisTech, Centre de Biotechnologies Agroindustrielles, AgroParisTech INRA, UMR 782 Genie & Microbiologie des Procedes Alimentaires, F-78850 Thiverval Grignon, France b INRA, Centre de Biotechnologies Agroindustrielles, AgroParisTech INRA, UMR 782 Genie & Microbiologie des Procedes Alimentaires, F-78850 Thiverval Grignon, France c Institut Pasteur de Lille, Lactic Acid Bacteria & Mucosal Immunity, Center for Infection and Immunity of Lille UMR 8204, 1 rue du Pr Calmette, BP 245, F-59019 Lille, France article info Article history: Received 12 September 2014 Received in revised form 17 January 2015 Accepted 5 March 2015 Available online xxx Keywords: Smear-cheese microflora Cheese In vitro model of digestion Murine in vivo model abstract A mixture of nine microorganisms (six bacteria and three yeasts) from the microflora of surface-ripened cheeses were subjected to in vitro digestive stress in a three-compartment “dynamic gastrointestinal digester” (DIDGI). We studied the microorganisms (i) grown separately in culture medium only (ii) grown separately in culture medium and then mixed, (iii) grown separately in culture medium and then included in a rennet gel and (iv) grown together in smear-ripened cheese. The yeasts Geotrichum can- didum, Kluyveromyces lactis and Debaryomyces hansenii, were strongly resistant to the whole DIDGI process (with a drop in viable cell counts of less than <1 log CFU mL 1 ) and there were no significant differences between lab cultures and cheese-grown cultures. Ripening bacteria such as Hafnia alvei survived gastric stress less well when grown in cheese (with no viable cells after 90 min of exposure of the cheese matrix, compared with 6 CFU mL 1 in lab cultures). The ability of Corynebacterium casei and Staphylococcus equorum to withstand digestive stress was similar for cheese and pure culture conditions. When grow in a cheese matrix, Brevibacterium aurantiacum and Arthrobacter arilaitensis were clearly more sensitive to the overall digestive process than when grown in pure cultures. Lactococcus lactis displayed poorer survival in gastric and duodenal compartments when it had been grown in cheese. In vivo experiments in BALB/c mice agreed with the DIDGI experiments and confirmed the latter's reliability. © 2015 Published by Elsevier Ltd. 1. Introduction Cheese is one of the oldest ways of conserving milk: in Northern Europe, evidence of cheese-making activity has been found at sites dating from the sixth millennium BC (Salque et al., 2013). At present, Europe produces around 9000 thousand tons of cheese per annum (Eurostat, 2013), and Europeans eat between 25 and 30 kg of cheese per capita per annum. Given that a gram of cheese contains 10 8 e10 9 living microorganisms on average (Beresford et al., 2001), the annual intake of viable cells can be estimated at 10 13 e10 14 per capita per annum. The complexity of microflora depends on the type of cheese. In Cheddar and mozza- rella, the microflora is relatively simple and consists mainly of lactic acid bacteria (LAB) and a few species of yeast (Kindstedt et al., 2004; Lawrence et al., 1993). In contrast, the microflora in soft, smear-ripened cheeses such as Livarot or Munster contains a broad, diverse range of bacteria and yeasts (Bockelmann, 2002; Irlinger and Mounier, 2009). Thus, a fermented food product like cheese is an important source of diverse microorganisms in the human diet. However, few studies have investigated the survival of the cheese microflora in the gastrointestinal tract. A review of the literature shows that most of the research in this field has focused on Lactobacilli, Bifidobacteria and Propionibacteria (Cousin et al., 2011; Saarela et al., 2000) with a view to find new probiotics or * Corresponding author. Tel.: þ33 130 815 388; fax: þ33 130 815 597. E-mail addresses: nadege.adouard@grignon.inra.fr (N. Adouard), laurent. magne18@gmail.com (L. Magne), thomas.cattenoz@grignon.inra.fr (T. Cattenoz), guillemi@grignon.inra.fr (H. Guillemin), benoit.foligne@ibl.cnrs.fr (B. Folign e), picque@grignon.inra.fr (D. Picque), pascal.bonnarme@grignon.inra.fr (P. Bonnarme). Contents lists available at ScienceDirect Food Microbiology journal homepage: www.elsevier.com/locate/fm http://dx.doi.org/10.1016/j.fm.2015.03.002 0740-0020/© 2015 Published by Elsevier Ltd. Food Microbiology xxx (2015) 1e11 Please cite this article in press as: Adouard, N., et al., Survival of cheese-ripening microorganisms in a dynamic simulator of the gastrointestinal tract, Food Microbiology (2015), http://dx.doi.org/10.1016/j.fm.2015.03.002