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Gari is a common cassava precooked dried semolina in sub‐Saharan Africa. Our study investigated the role of process parameters and mash water content on gari quality during traditional roasting stage. The statistical analysis for eight quality criteria revealed that gari quality is highly influenced by the process parameters adopted by the operators. To emphasise the twin impact of roasting parameters and mash water content, different mashes with varying water content were roasted leading to different adjustments of the roasting conditions according to the operators. When the variability of the water content becomes greater, a greater variability in the final quality of the obtained garis was observed between operators (lightness, swelling capacity, starch content, texture and colour). These results suggest that technological improvements to the gari process could be achieved by appropriate management of the roasting and dewatering parameters., Role of process parameters in gari quality during handmade roasting of mashes with different water content.

L’ouvrage fait suite à un projet multipartenarial de sciences participatives, nommé FLEGME. Ce projet a vu le jour dans l’ouest de la France en 2019, il a pour objectif de proposer et de mettre en avant, une conservation plus durable des légumes et une diversification de leur mode de consommation.Ce guide des techniques et savoirs liés à la lactofermentation des légumes est issu d’un travail collaboratif, avec une implication forte des acteurs du réseau créé par le projet FLEGME. Son objectif est de proposer des pistes pour réussir un projet de fabrication/vente de légumes lactofermentés. Il se structure en quatre temps : contexte historico-culturel et social, l’angle scientifique, les modes opératoires et les étapes de fabrication des légumes lactofermentés dans un contexte de transformation en ateliers de petite taille, et un dernier chapitre aborde les questions marketing et commerciales pour bien vendre.

Les interactions impliquant les bactéries lactiques (BL), responsables des propriétés sanitaires, organoleptiques et santé des produits fermentés, sont souvent étudiées en association avec des levures ou des bactéries propioniques dans divers produits alimentaires fermentés et les mécanismes de leurs interactions sont assez bien caractérisés. En ce qui concerne les interactions entre BL, elles ont principalement été étudiées pour tester des interactions antagonistes. Comprendre comment les BL peuvent interagir positivement serait utile dans de multiples domaines liés à l'alimentation, comme la production de produits fermentés aux propriétés fonctionnelles améliorées ou la fermentation de nouvelles matrices alimentaires. Les dépendances nutritionnelles, notamment celles vis-à-vis des sources d'azote, régissent de nombreuses interactions positives microbiennes. De telles interactions positives ont déjà été étudiées entre les BL du yaourt. Cependant, elles n'ont jamais été exploitées pour créer des co-cultures de BL issues de biotopes différents. L'objectif de cette étude était de favoriser les interactions positives entre BL, basées sur les dépendances aux sources d’azote dans les co-cultures pour augmenter les taux d'acidification, la consommation de sucres comme le raffinose et la production de composés volatils. La stratégie consistait à exploiter les activités protéolytiques et les auxotrophies des acides aminés des BL. Un milieu chimiquement définia été développé pour permettre spécifiquement la croissance des six souches de BL utilisées, trois protéolytiques et trois non protéolytiques. Chacune des souches protéolytiques, Enterococcus faecalis CIRM-BIA2412, Lactococcus lactis NCDO2125 et CIRM-BIA244, a été cultivée avec chacune des souches de BL non protéolytiques : L. lactis NCDO2111, Lactiplantibacillus plantarum CIRM-BIA465 et CIRM-BIA1524. La croissancebactérienne a été suivie à l'aide de chambres compartimentées pour comparer la croissance en mono- et co-cultures. Chaque souche protéolytique a induit différents types d'interactions 2 : fortement positives avec E. faecalis CIRM-BIA2412, faiblement positives avec L. lactis NCDO2125, ou nulles avec L. lactis CIRM-BIA244. En co-cultures directes, les interactions ont conduit à des taux d'acidification plus rapides, à un pH final plus bas, à une utilisationplus élevée du raffinose et à des concentrations plus élevées en cinq composés volatils, pouvant donner des arômes intéressants. Les fortes interactions étaient associées à des concentrations plus élevées en tryptophane, valine, phénylalanine, leucine, isoleucine et en peptides. Une analyse peptidomique a permis d’identifier les acides aminés hydrophobes et à chaîne ramifiée comme essentiels dans ces interactions. Cette étude donne un nouvel aperçu des mécanismes régissant les interactions entre BL et offre des solutions pour améliorer ou concevoir des ferments lactiques.

Fermented food are an important part of our diet and of gastronomical cultures around the globe.The microorganisms composing them develop in an environment controlled by humans and can thus be domesticated. Because the microbial communities of fermented foods are generally relatively simple, they can be good models for microbial ecology and domestication studies. My PhD focuces on the microbial communities of sourdough bread and of a traditional fermented milk from Brittany region called Gwell. These two products are maintained by back-slopping, i.e. a part of a previous production is used to inoculate the next one. They are thus maintained by the producers, sometimes during several years. The first part of my thesis consisted in studying the dispersal of microorganisms. I showed that the flour added to sourdough during the microbial communitiess did not introduce new fermenting microorganisms into the mature sourdough, and that the exchange of ferments between Gwell producers resulted in two lineages of Gwell with distinct microbial communities. The second part of my thesis focused on the stability of microbial community during their maintenance by producers. My results showed that most bakers maintained the same dominant fermentative yeast species in their sourdough over years,as long as they did not change bakery, bakers, or initiate a new sourdough. With respect to Gwell, we conducted an in-farm experimental evolution assay with three Gwell producers. We showed that an increased frequency of back-slopping resulted in a faster acidification of the Gwell, because thebacterial species mainly responsible for the acidification in Gwell was more resistant to cold shocks and was thus favored. Our results further suggested that Gwell bacteria adapted over the long term to the back-slopping practices of the producer. My thesis was conducted using a participatory approach, with producers taking part in one or more steps of the research process, from the development of the researchquestions to the analysis of the results. This approach allowed us to share our empirical and scientific knowledges on fermented food. These exchanges took the form of training session, meetings for the preparation of the experimentation, synthesis of results, or informal exchanges, as the research process progressed., Les aliments fermentés représentent une part importante de notre alimentation et des différentes cultures gastronomiques à travers le monde. Les microorganismes qui les composent se développent dans un environnement contrôlé par des humains et sont donc susceptibles d’être domestiqués. La communauté microbienne des aliments fermentés étant généralement relativement simple, ils peuvent constituer de bons modèles en écologie microbienne et pour les études de domestication des microorganismes. Ma thèse a porté sur les communautés microbiennes du levain de panification et d’un lait fermenté traditionnel breton nommé Gwell. Ces deux produits sont entretenus par back-slopping, c’est à dire qu’une partie d’une production précédente est utilisée pour inoculer la suivante. Ils sont ainsi entretenus par les producteurs parfois pendant plusieurs années de manière continue. La première partie de ma thèse a consisté à étudier la dispersion des microorganismes. J’ai montré que la farine apportée au cours des back-slopping n’introduisait pas de nouveaux microorganismes fermentaires dans le levain de panification mature, et que les échanges de ferments entre producteurs de Gwell avaient donné lieu à deux lignées de Gwell dont les communautés microbiennes étaient distinctes. La seconde partie dema thèse a porté sur la stabilité des communautés microbiennes au cours de leur entretien par les producteurs. Les résultats obtenus ont montré que les boulangers conservaient pour la plupart l’espèce fermentaire majoritaire de leur levain tant qu’ils ne changeaient pas de locaux ni de personne en charge du levain ou n’initiaient pas un nouveau levain. En ce qui concerne le Gwell, nous avons réalisé avec trois producteurs un essai d’évolution expérimentale en fromagerie. Nous avons montré qu’une fréquence accrue de back-slopping du Gwell entraînait une acidification plus rapide du lait, car l’espèce de bactérie principalement responsable de l’acidification dans le Gwell était plus résistante aux chocs thermiques et était donc favorisée. Nos résultats suggèrent de plus que les bactéries du Gwell se sont adaptées sur le long terme aux pratiques de back-slopping de leur producteur. Ma thèse a été menée avec une approche de recherche participative, les producteurs prenant part à une ou plusieurs étapes du processus de recherche, de l’élaboration des questions de recherche à l’analyse des résultats. Cette approche a permis de mettre en commun nos connaissances scientifiques et empiriques des produits fermentés et d’échanger des savoirs. Ces échanges ont pris la forme de formations, de réunions de préparation desexpérimentations, de synthèse des résultats, ou de manière informelle, chemin faisant au cours de la réalisation du projet de recherche.

International audience; Les aliments fermentés représentent une part importante de la diète. Ils sont issus de la fermentation spontanée ou dirigée de nombreuses matières premières végétales ou animales et représentent une très grande variété de produits. Ils font l’objet d’un regain d’attention sociétal, du fait notamment des propriétés santé qui leur sont attribuées. Ces bénéfices santé potentiels peuvent reposer sur l’apport des microorganismes eux-mêmes - dont beaucoup atteignent vivants l’intestin - et/ou sur l’apport de métabolites spécifiques issus de l’activité de ces microorganismes. Des études interventionnelles et des études de cohortes récentes démontrent des effets bénéfiques de la consommation d’aliments fermentés. De nombreux efforts de recherche sont cependant nécessaires pour comprendre les mécanismes impliqués et donner à ce groupe d’aliments particuliers la place qui leur revient.

National audience; Toutes les matières premières consommables-animales et végétales ,solides ou liquides- peuvent être fermentées.Outre ses effets bénéfiques pour la santé,ce procédé contribue à la sécuritéalimentaire mondial

International audience; Nutritional dependencies, especially those regarding nitrogen sources, govern numerous microbial positive interactions. As for lactic acid bacteria (LAB), responsible for the sanitary, organoleptic, and health properties of most fermented products, such positive interactions have previously been studied between yogurt bacteria. However, they have never been exploited to create artificial co-cultures of LAB that would not necessarily coexist naturally, i.e from different origins. The objective of this study was to promote LAB positive interactions, based on nitrogen dependencies in co-cultures, and to investigate how these interactions affect some functional outputs, e.g. acidification rates, carbohydrate consumption, and volatile compound production. The strategy was to exploit both proteolytic activities and amino acid auxotrophies of LAB. A chemically defined medium was thus developed to specifically allow the growth of six strains used, three proteolytic and three non-proteolytic. Each of the proteolytic strains, Enterococcus faecalis CIRM-BIA2412, Lactococcus lactis NCDO2125, and CIRM-BIA244, was co-cultured with each one of the non-proteolytic LAB strains: L. lactis NCDO2111, Lactiplantibacillus plantarum CIRM-BIA465 and CIRM-BIA1524. Bacterial growth was monitored using compartmented chambers to compare growth in mono- and co-cultures. Acidification, carbohydrate consumption and volatile compound production was evaluated in direct co-cultures. Each proteolytic strain induced different types of interactions: either strongly positive, weakly positive, or no interactions, with E. faecalis CIRM-BIA2412, L. lactis NCDO2125 and L. lactis CIRM-BIA244, respectively. Strong interactions were associated with higher concentrations in tryptophan, valine, phenylalanine, leucine, isoleucine, and peptides. They led to faster acidification rates, lower pH, higher raffinose utilization and concentrations in five volatile compounds. Importance: Lactic acid bacteria (LAB) interactions are often studied in association with yeasts or propionibacteria in various fermented food products and the mechanisms underlying their interactions are being quite well characterized. Concerning interactions between LAB, they have mainly been investigated to test antagonistic interactions. Understanding how they can positively interact could be useful in multiple food-related fields: production of fermented food products with enhanced functional properties or fermentation of new food matrices. This study investigates the exploitation of the proteolytic activity of LAB strains to promote positive interactions between proteolytic and non-proteolytic strains. The results suggest that proteolytic LAB do not equally stimulate non-proteolytic LAB and that the stronger the interactions between LAB are, the more functional outputs we can expect. Thus, this study gives insight into how to create new associations of LAB strains and to guaranty their positive interactions.

International audience; Flavor is an important property of fermented foods and largely results from the production of aroma compounds by microorganisms. In smear-ripened cheese varieties, surface microbiota is thought to contribute to the typicity of the aroma. Our objective was to identify key odorants in smear-ripened semi-hard cheese and the role of surface microbiota in their production. The strategy used was to generate three groups of cheeses from the same curd, which was ripened under regular conditions (C) or under two types of oxygen-barrier wrapping films (A and B), so as to prevent the growth of surface microbiota. Two extraction methods, head space trap (HST) and solvent-assisted flavor evaporation (SAFE), were coupled to gas chromatography-mass spectrometry (GC-MS). GC-MS/olfactometry was used to identify the most potent odorants. Cheeses were evaluated by sensory profiling. The three cheese groups had the same gross composition and pH in the core (5.48 ± 0.07). In contrast, cheeses C differed from the two other cheese groups. It had a higher pH at the surface (5.96 versus 5.51 in A and B), showed 10% more proteolysis, contained 2 to 3-fold more succinic and acetic acids and less lactic acid (8.1 g/kg in C versus around 14 g/kg in cheeses A and B). Moreover, one third of the volatile compounds detected by HST-GC-MS were present in a significant greater abundance in cheese C than in cheeses A and B, including a range of compounds arising from amino acid catabolism and lipolysis likely associated with surface microbiota activity. Twelve out of the 20 odorants identified by SAFE-GC-MS/olfactometry received higher olfactometry scores in cheese C. Cheese C were also characterized by a stronger and typical flavor and odor. These results contribute to a better knowledge of key odorants in smear-ripened cheeses and confirm the crucial role of surface microbiota in their production.

International audience

Engineering school

International audience; Fermentation allows to preserve food in a sustainable way at a lower cost and contributes to the world food security. This method of preservation is currently very popular with a population in search of naturalness. Health virtues are also attributed to fermented foods because they contain living micro-organisms or specific macro- and micronutrients. Are these products, or the fermentation process, as such really beneficial to health?; La fermentation permet de conserver de manière durable les aliments à moindre coût dans de nombreux pays et participe grandement à la sécurité alimentaire mondiale. Ce mode de conservation est actuellement très prisé par une population en recherche de naturalité. Des vertus santé sont également attribuées aux aliments fermentés parce qu’ils contiennent des microorganismes vivants ou des macro-micronutriments spécifiques. Ces produits, très divers, ou le processus de fermentation en tant que tel sont-ils bénéfiques pour la santé ?

Artisanal fermented foods are highly appreciated by consumers for their typical organoleptic and nutritional properties which depend on the metabolic activities of autochthonous microorganisms encountered during the fermentation process. This PhD project aimed at deciphering the microbial diversity and determining its impact on the final biochemical properties of two artisanal Mediterranean products: Pélardon, a raw goat milk cheese, and Nyons black table olives. Microbial communities were analyzed by a cultural approach and metagenetics and both products revealed rich fungal and bacterial diversity. By correlating microbial data with biochemical changes throughout the process, key species could be linked to the changes observed during the different fermentation stages for both products. Discrepancies were however observed between the two approaches for both fermentations thus confirming the interest of combining both methods to comprehensively study microbial diversity and dynamics in an unbiased way. Microbial sources were also investigated and showed that the process environment constituted a major microbial reservoir compared to raw materials (raw milk and olive fruits) for these natural fermentations.Finally, a tailor-made complex autochthonous yeast consortium was designed and used in directed fermentations of Nyons table olives. Promising results were obtained, especially for a salt-reduced fermentation. These results evidently highlighted the interest of exploiting autochthonous microorganisms without altering the typicity and know-how associated with artisanal fermented foods.; Les aliments fermentés artisanaux sont particulièrement appréciés des consommateurs pour leurs caractéristiques organoleptiques et nutritionnelles, qui sont étroitement liées à l’action des micro-organismes intervenant pendant leur fabrication. L’objectif de cette thèse était d’étudier la diversité microbienne et son influence sur les caractéristiques biochimiques de deux produits méditerranéens artisanaux préparés par fermentation naturelle : le Pélardon, un fromage de chèvre au lait cru et les olives noires de Nyons. Les deux produits se sont révélés porteurs d’une grande diversité de micro-organismes (bactériens et fongiques). L’analyse de communautés microbiennes, par méthode culturale et métagénétique, corrélée aux changements biochimiques, a permis de mettre en évidence les micro-organismes clés impliqués dans les diférentes étapes de fabrication.Des divergences observées entre les deux méthodes ont aussi montré l’intérêt de les combiner pour élucider la diversité et la dynamique des communautés sans biais. Par ailleurs, les travaux menés sur l’origine des micro-organismes ont montré que l’environnement de production constituait un réservoir microbien important par rapport aux matières premières (lait cru et olives) lors de ces fermentations traditionnelles.Enfin, une culture complexe de levures autochtones a été élaborée et mise en œuvre dans des fermentations dirigées d’olives de Nyons. Les résultats ont été prometteurs, surtout dans le cas d’une fermentation réalisée à un taux de sel réduit, soulignant l’intérêt de l’exploitation des micro-organismes autochtones sans compromettre la typicité et le savoir-faire associés au produit.

Fermentation by microorganisms is a key step in the production of traditional food products such as bread, cheese, beer and wine. In these fermentative ecosystems, microorganisms interact in various ways, namely competition, predation, commensalism and mutualism. Traditional wine fermentation is a complex microbial process performed bySaccharomycesand non-Saccharomyces(NS) yeast species. To better understand the different interactions occurring within wine fermentation, isolated yeast cultures were compared with mixed co-cultures of one reference strain ofS. cerevisiaewith one strain of four NS yeast species (Metschnikowia pulcherrima, M. fructicola, Hanseniaspora opuntiae and H. uvarum). In each case, we studied population dynamics, resource consumed and metabolites produced from central carbon metabolism. This phenotyping of competition kinetics allowed us to confirm the main mechanisms of interaction between strains of four NS species.S. cerevisiaecompeted withH. uvarumandH. opuntiaefor resources although bothHanseniasporaspecies were characterized by a strong mortality either in isolated or mixed fermentations.M. pulcherrimaandM. fructicoladisplayed a negative interaction with theS. cerevisiaestrain tested, with a decrease in viability in co-culture, probably due to iron depletion via the production of pulcherriminic acid. Overall, this work highlights the importance of measuring specific cell populations in mixed cultures and their metabolite kinetics to understand yeast-yeast interactions. These results are a first step towards ecological engineering and the rational design of optimal multi-species starter consortia using modeling tools. In particular the originality of this paper is for the first times to highlight the joint-effect of different species population dynamics on glycerol production and also to discuss on the putative role of lipid uptake on the limitation of some non-conventional species growth although interaction processes.

Consumption of fumonisin-contaminated foods has a negative influence on the health of humans (carcinogen; oesophageal cancer in Eastern Cape in South Africa). Lactic acid bacteria (LAB) have emerged as a promising natural detoxification agent against mycotoxins. The aim of this study was to visualise the interaction between fumonisins (FB1 and FB2) and LAB: Lactobacillus plantarum FS2, L. delbrueckii subsp. delbrueckii CIP 57.8T and Pediococcus pentosaceus D39, isolated from traditional fermented maize-based products (ogi and mahewu) using confocal laser scanning microscopy (CLSM) and to then quantify the LAB-bound fumonisin using high performance liquid chromatography (HPLC). The objective was to obtain a physically visible and quantifiable binding interaction between fumonisins and LAB strains with the aim of utilising LAB as a possible detoxifying agent. Fumonisins were derivatised using naphthalene-2,3-dicarboxaldehyde (NDA) and then combined with non-fluorescent LAB cells (viable and non-viable). For the quantification of bound fumonisins, viable and non-viable cells were incubated in the presence of predetermined concentrations of fumonisins and the level of fumonisin in the suspension was determined. CLSM showed the derivatised green fluorescent fumonisins binding to the surface of each of the LAB cells. For viable cells, L. plantarum FS2 bound FB1 most effectively while P. pentosaceus D39 bound the least level of FB1. The highest levels of FB2 were bound by L. plantarum R 1096 and the least by L. delbrueckii CIP 57.8 T. For non-viable cells, L. plantarum FS2 was also the most effective for binding both fumonisins with P. pentosaceus D39 and L. delbrueckii CIP 57.8 T being the least effective for FB1 and FB2, respectively. To our knowledge, this is the first study to visualise the interaction between LAB and fumonisins. We demonstrate that LAB isolates from indigenous fermented maize-based beverages bind fumonisins and thus present a potential strategy for their reduction in these traditional foods.

Ablo is a rice or maize-based steam-cooked bread-like product, very popular in Benin, Togo and Ghana. This study optimized the processing steps of rice ablo using response surface methodology. The effect of precooking (proportions of flour and water, duration), kneading (wheat level, duration), fermentation (yeast level, temperature, duration) conditions to dough (gelatinization level, fluidity, proofing) and ablo (ethanol content, pH, density, cooking expansion, firmness, alveolar structure) properties were studied. It was demonstrated that ablo texture can be controlled by the fluidity of the fermented dough. Fluid fermented dough (at least 0.5 cm/s) expands adequately during steam-cooking and results in a less dense ablo in line with commonly consumed ablo. The optimal dough fluidity comes from a low gelatinization level of the precooked dough (less than 20%) and an intense fermentation (high yeast dose and long fermentation). Surprisingly, dough proofing appears to have no effect on final ablo expansion.

Florilège : une base de données de phénotypes microbiens d’intérêt agro-alimentaire .. Journées qualiment

International audience; For thousands of years, locally and internationally, a particular family of foods exists in our diet: the fermented foods. These “living” foods, shaped by micro-organisms, have microbiological, biochemical and physicochemical characteristics that are very different from the raw material they are made of. Consequently, they have been granted with many nutritional and health benefits, although the studies that have been conducted on these foods are not sufficient and can hardly be generalised (i.e.: to a generic effect). However, in the current context of expectations of sustainability and naturalness, it is clear that these foods could have a central role to play in our food systems. The issue concerning their health value, especially in the light of new knowledge on the gut microbiota, needs to be clarified in order to consider the place of fermented foods in dietary recommendations.; Depuis des millénaires, localement et à l’échelle internationale, existe dans notre diète une famille d’aliments particuliers : les aliments fermentés. Ces aliments « vivants », façonnés par des micro-organismes, ont des caractéristiques microbiologiques, biochimiques et physico-chimiques très différentes de la matière première dont ils sont issus. De ce fait, ils ont été parés de nombreuses vertus nutritionnelles et de santé bien que les études qui ont été réalisées sur ces aliments soient insuffisantes et peinent à esquisser un effet générique. Cependant, dans le contexte actuel des attentes de durabilité et de naturalité, il est clair que ces aliments pourraient avoir un rôle central à jouer dans nos systèmes alimentaires. La question de leur valeur santé, au regard notamment des nouvelles connaissances sur le microbiote intestinal, doit être clarifiée pour pouvoir considérer la place des aliments fermentés dans les recommandations alimentaires.

International audience; This study explores the ability of lactic acid bacteria (LAB) to ferment soy juice. The ability of 276 LAB strains from 25 species to ferment the principal soy carbohydrates, sucrose, raffinose or stachyose was tested in synthetic media and a soy juice. Fermented soy juices (FSJs) were characterized for their odor. Selected FSJs were characterized by targeted metabolomics. All Streptococcus, 83% of Leuconostoc and Lactobacillus and 41% of Lactococcus strains were sucrose-positive, while only 36% of all the LAB strains tested were raffinose-positive and 6% stachyose-positive. Nearly all (97%) the sucrose-positive strains fermented soy juice, indicating that an ability to use sucrose is a good criterion to select strains for soy juice fermentation. Among the most efficient acidifying strains, 46 FSJs had an odor deemed to be acceptable. FSJ composition was dependent on both species and strains: 17/46 strains deglycosylated soy juice isoflavones, the 27 S. thermophilus strains converted a mean 4.4 ± 0.1 g/L of sucrose into 3.0 ± 0.1 g/L of lactic acid versus 5.2 ± 0.1 g/L into 2.2 ± 0.1 g/L for the 18 Lactobacillus and one Lactococcus strains. This study highlights the diversity of the metabolic profiles of LAB strains in soy juice fermentation.

National audience; A Western diet containing 50% of plant-based protein is healthier and would help to reduce the environmental impacts of food systems to contribute to meeting worldwide protein needs. However, few consumers do like plant-based protein food, 25% of consumers do like taste of soy products. Fermentation by lactic acid bacteria (LAB) is a sustainable and an inexpensive process for the preservation or raw material that can also modify taste. In this work, we screened 278 LAB in order to select strains of interest to ferment soy juice. Our findings showed that the ability of LAB to ferment soy juice is both species- and strain-dependent. We also found that some strains can improve organoleptic properties of fermented soy juices, and the study highlights the diversity of metabolic profiles of LAB in soy juice fermentation. In conclusion, specific LAB can improve plant-based product fermentation rates, organoleptic properties and thus help to promote plant-based proteins in our diet.

This study identified biogenic amines, fatty acids, and volatile compounds in adjuevan, an Ivorian traditionally salted and fermented fish. Samples were obtained from two processing methods (method 1: entire fish adjuevan; method 2: both sides filleted adjuevan) with the fish species Galeoides decadactylus. Biogenic amines found in freshly produced adjuevanwere histamine, putrescine, cadaverine, tyramine, -phenyl ethylamine, and spermidine. Among these, the most prevalent were -phenyl ethylamine and cadaverine. Biogenic amine contents varied according to the processing method but re-mained lower than levels considered hazardous for human health. The major fatty acids present in adjuevan from method 1 were docosahexaenoic acid, palmitic acid, and oleic acid. In adjuevan from method 2, the major fatty acids were oleic acid, stearic acid, and palmitic acid. The omega ()-3/-6 ratio was 8.87 and 4.12 for adjuevan from methods 1 and 2, respec-tively. Most of the fatty acids are considered healthy fats, making adjuevan a useful food for treating and preventing life-style diseases. The volatile compounds found composed of 19 aldehydes, 12 alcohols, 7 esters, 7 ketones, 3 furans, 10 aro-matic compounds, and 7 acids with aldehyde, alcohol, and ester compounds as the predominant groups. Among the alde-hydes, 2,4-heptadienal (E,Z), octanal, and 2-octenal (E) were most prevalent in adjuevan from method 1, whereas 2-none-nal (E), 2,4-heptadienal (E,Z), and octanal were most prevalent in adjuevan from method 2.

book available at: https://fems2019.org/abstracts/abstract-book/; Kombucha is an increasingly popular traditional beverage obtained by fermenting sweetened tea in the presence of a microbially rich floating biofilm. The final product contains many organic acids and CO2 and may also contain low levels of ethanol along with other metabolites. During fermentation, a symbiotic relationship between yeasts and acetic acid bacteria and, in some cases, lactic acid bacteria has been described. Our previous work on industrial scale fermentations highlighted that Acetobacter, Gluconobacter, Gluconacetobacter, Komagataeibacter and Oenococcus bacterial genera and Dekkera, Zygosaccharomyces and Hanseniaspora yeast genera could be of technological importance for Kombucha fermentations.The goal of this study was to dynamically follow a lab scale Kombucha fermentation using a selected microbial consortium. Metagenetics (bacteria and yeast), microbiological, physico-chemical and biochemical (organic acids by LC-QTOF, volatiles by GC-MS) parameters were followed as well as biofilm formation using FISH-confocal microscopy and scanning electron microscopy over 27 days.Results showed sugar consumption by the microbial consortium and the successive production of multiple organic acids (especially acetic, lactic, gluconic and glucuronic acids) and volatile compounds, particularly volatile fatty acids, alcohols and their corresponding esters as well as a decrease in aldehydes over time. Active biofilm formation by acetic acid bacteria could also be monitored by microscopy and highlighted the distinct presence and positioning of the different microbial groups.These results provide novel information on the microbial dynamics of species within a defined consortium and their functional roles during fermentation and should lead to better fermentation control and product quality in the future.

Les produits fermentés sont consommés dans le monde entier depuis des siècles. Les végétaux fermentés font l’objet d’un regain d’intérêt, suivant les tendances du végétarisme, de la recherche de naturalité et du développement durable. Le CTCPA et le pôle de compétitivité VEGEPOLYS vous proposent ce séminaire de formation, au cours duquel leurs intervenants feront le point sur les tendances de ce marché, sur l’état de l’art et les limites des connaissances techniques et scientifiques sur le sujet.

Artisanal fermented foods represent a cultural heritage that needs to be preserved and protected; this is particularly true in the context of industrial food standardization. The manufacture and unique sensorial properties of such products mainly relies on autochthonous complex microbiota and their activities. The present study focuses on Pélardon, a Protection Designation of Origin (PDO) French artisanal soft rind cheese, exclusively produced from raw goat’s milk using a back slopping method in mountainous areas in southern France. Pélardon microbial ecology and dynamics were studied by culture-dependent and -independent methods. A complete production was followed at an artisanal cheese-making factory and sampling was performed at different cheese-making steps from the raw milk to cheese ripened for 3 months. Different population were monitored on different media. Fungal and bacterial isolates were collected and identified. The achieved results were compared to metabarcoding analyses targeting ITS 2 region for Fungi and V3-V4 region of the 16S RNAr for Bacteria. Focusing on cultivable microorganisms, higher microbial populations were observed in whey used for inoculation compared to raw milk. Results also highlighted the importance of fungi. Despite the initial low inoculum, yeast growth began as early as milk acidification and during the renetting step. Metagenetic results outlined the differences in both fungal and bacterial communities between cheese rind and core samples. Bacterial diversity increased during the ripening specially in the rind compared to the curd stage. Although yeasts were present early in the processing, fungal diversity remained limited at the end of ripening. To better understand the origin of the observed microbial diversity, environmental and raw material samples were also investigated and ongoing work should provide new insights about the dynamics of these microbial communities.

1. IntroductionFermented foods are complex biological ecosystems, harbouring diverse microbial communities which contribute to the quality of these food products. In most industrial processes, these communities are advisedly chosen as starter culture for their adaptation to: (i) the substrates to be fermented (milk, vegetable) (ii) the process (°C, O2, NaCl) and (iii) the desired overall quality of the food product in terms of texture, flavour, nutrition and health benefits. For this purpose, technological properties have been mainly assessed by a time-consuming in vitro screening. We hypothesis that the huge amount of bibliographic and microbial genomic data available in public databases would enable an in silico preselection of the strains of interest before wet laboratory screening experiments.2. ObjectivesOur aim was to provide (i) adapted bioinformatic tools to mine the diversity of microbial technological properties and metabolisms (ii) a strategy to preselect strains based on their phenotypes and on their genetic potential (sugar utilization, aroma production).3. Material and MethodsWe used a bioanalysis approach to provide insight into the presence of enzyme-encoding genes responsible for targeted technological properties. KEGG, Metacyc, NCBI and CAZY databases were queried by a search on enzyme numbers, names and sequence alignments. We developed Florilege (http://migale.jouy.inra.fr/Florilege/), a database of microbial phenotypes based on text-mining to gather microbial growth conditions.4. ResultsCombining both approaches, we set up a bioinformatic preselection of lactic acid bacteria able to degrade sugar from milk, cereal or legume based juice to develop yogurt-like products. Database queries provided a list of microbial species with genes encoding key targeted enzymes. A set of preselected anaerobic, mesophilic and thermophilic strains has been successfully screened on different milk and juice in our wet laboratory providing potential new starter strains.5. ConclusionThe developed tools and the strategy can be usefully applied to other domains like bioremediation and white biotechnology.

L’UCO de Guingamp vous propose de nous réunir lors de la 3ème édition de notre évènement U’COOK-INNOVATION autour de la thématique les « Les Produits Fermentés » : UN THÈME FÉDÉRATEUR ET TENDANCE Il nous renvoie à notre RESPONSABILITE de développer une consommation saine, équilibrée & durable dans le monde UN AXE STRATÉGIQUE DE DÉVELOPPEMENT pour de nombreuses entreprises face à la croissance de la demande des consommateurs PLUSIEURS QUESTIONS se posent alors sur ces produits : la qualité, le goût, le prix, l’aspect nutrition/santé, la certification, leurs limites… 6 INTERVENANTS EXPERTS DANS LEUR MÉTIER expliqueront le rôle et les enjeux de la fermentation : marché, coûts, limites, implications…Un focus sera fait sur les différentes fermentations (procédés, points communs et différences) sur le microbiote digestif et sur les bienfaits immunitaires et digestifs, sans oublier les limites d’une consommation excessive.

From strain potential to bacterial community design for targeted functions. STLOpendays

Smart design of functional fermented dairy foods . STLOpendays

White Kenley is a traditional stiff dumpling produced from fermented dehulled maize grains in Ghana. The physico-chemical modifications which occur during combination of various steeping (12, 30 and 48 h) and fermentation (0 h, 12 h and 24 h) times were assessed to study the impact of these unit operations on the quality of white kenkey . Water uptake by soaked grains and the release of metabolites were followed during grains steeping and particle size distribution after milling was determined. Steeping time exceeding 24 h was required to produce a fine wet milled flour while water uptake was completed after 8–10 h. This was parallel to hydrolysis of proteins and/or hemicelluloses which occurred after 16 h. Changes in acidity and glucose content were determined in the grain after steeping and in the dough after fermentation. The texture of the kenkey was determined using a texture analyzer. Increases in acidity were higher during dough fermentation than in steeping. Stickiness of the white kenkey decreased consistently with steeping time. Principal Component Analysis showed that a combination of long steeping and short fermentation times gives white kenkey with low stickiness (and high fineness), low acidic taste and low fermented odour.

International audience; Fungi are commonly identified as the cause for dairy food spoilage. This can lead to substantial economic losses for the dairy industry as well as consumer dissatisfaction. In this context, biopreservation of fermented dairy products using lactic acid bacteria, propionibacteria and fungi capable of producing a large range of antifungal metabolites is of major interest. In a previous study, extensive screening was performed in vitro and in situ to select 3 dairy fermentates (derived from Acidipropionibacterium jensenii CIRM-BIA1774, Lactobacillus rhamnosus CIRM-BIA1952 and Mucor lanceolatus UBOCC-A-109193, respectively) with antifungal activity. The aim of the present study was to determine the main compounds responsible for this antifungal activity. Fifty-six known antifungal compounds as well as volatiles were targeted using different analytical methods (conventional LC and GC, GC–MS, LC-QToF). The most abundant antifungal compounds in P. jensenii-, L. rhamnosus- and M. lanceolatus-derived fermentates corresponded to propionic and acetic acids, lactic and acetic acids, and butyric acid,respectively. Many other antifungal compounds (organic acids, free fatty acids, volatile compounds) were identified but at lower levels. In addition, an untargeted approach using nano LC-MS/MS identified a 9-amino acid peptide derived from αs2-casein in the L. rhamnosus-derived fermentate. This peptide inhibited M. racemosus and R. mucilaginosa in vitro. This study provides new insights on the molecules involved in antifungal activities of food-grade microorganism fermentates which could be used as antifungal ingredients in the dairy industry.

les propionibactéries laitières, des bactéries particulières.. Invitation INRA TOXALIM

Fermented cereals are part of the main traditional diets of many people in Africa, usually obtained from artisanal production. The intensification of their manufacturing, responding to the consumers demand, requires a better control to ensure their sanitary, nutritional, and taste qualities, hence, the need of selecting accurate and safe starter cultures. In the present study, 48 lactic acid bacteria (LAB) strains, previously isolated from Algerian fermented wheat lemzeiet, were analyzed for different technological properties. 14 LAB strains, belonging to Pediococcus pentosaceus, Enterococcus faecium, Lactobacillus curvatus, Lactobacillus brevis, and Leuconostoc mesenteroides species, decreased rapidly the pH of the flour extract broth close to 4 or below. 91% of strains showed extracellular protease activity, but only 12% were amylolytics. 18 LAB strains inhibited or postponed the growth of three fungal targets Rhodotorula mucilaginosa UBOCC-A-216004, Penicillium verrucosum UBOCC-A-109221, and Aspergillus flavus UBOCC-A-106028. The strains belonging to Lactobacillus spp., Leuconostoc fallax, L. mesenteroides, and Weissella paramesenteroides were the most antifungal ones. Multiplex PCR for biogenic amines' production did not reveal any of the genes involved in the production of putrescine, histamine, and tyramine for 17 of the 48 strains. The obtained results provided several candidates for use as starter culture in the future production of lemzeiet.

Lactobacillus, Pediococcus, Oenococcus and Leuconostoc are the main Lactic Acid Bacteria (LAB) genera present in cider as they are able to survive this hostile environment. LAB play a significant role in cider quality, for example in the process of malolactic fermentation, even though they can also be involved in spoilage of cider (production of biogenic amines, exopolysaccharides, off-flavours…). In this context a better monitoring of the fermentation process is a matter of interest to guarantee cider quality. In the present study, we designed a genus-specific multiplex PCR for a rapid and simultaneous detection of the four main LAB genera involved in cider production. This multiplex PCR worked equally with purified genomic DNA of bacterial isolates and with colonies directly picked from agar plates. This new PCR method was also successfully extended to wine and dairy isolates, and thus constitutes an effective tool to quickly identify LAB associated with fermented foods. Moreover, many biodiversity studies would also benefit from this fast, cheap and reliable identification method.

Probiotic microorganisms may affect human health, partly by modulating the immune response. They are commensals, part of the natural human microbiota, or provided within fermented foods or within food supplements. As an example, some of them colonize the digestive tract at early stages of life and play a key role in the maturation of the immune system. Accordingly, a lack of implantation of these beneficial bacteria correlates with immune and inflammatory disorders, which constitute a growing health concern and are gradually understood, in the light of variations of the gut microbiota structure. Potential applications of probiotic bacteria further involve the treatment of diarrhoea caused by rotavirus, of allergy, of eczema, of irritable bowel syndrome and of inflammatory bowel diseases. The mechanisms underlying interactions between probiotic bacteria and the host thus constitute a hot topic. Surface molecules of probiotic bacteria play a central role in these interactions. Referred to as Microbe-associated Molecular Pattern (MAMP), these key molecules are recognized by corresponding pattern recognition receptors (PRR), present at the surface of the host cells. The role of MAMPs includes adhesion and modulation of the gut associated immune system, prior to that of the systemic immune system, by mediating a host/bacteria cross-talk. MAMPs include surface proteins, glycoproteins, lipoproteins, pilins, flagellins, as well as surface associated polysaccharides. Host PRRs, which can perceive MAMPs, include Toll-like receptors (TLR), as well as the C type lectin DC-specific intercellular adhesion molecule 3-grabbing non-integrin (DC-SIGN). They may be present at the surface of epithelial cells, and of dendritic cells. This oral presentation will illustrate the key role of probiotics’ MAMPs through examples of bifidobacteria, lactobacilli, and of propionibacteria. It will present textbook cases spanning from molecular to in vivo studies. Scientific data acquired during the last decade indeed place interactions between MAMP and PRR at the Centre of Probiotic/Host Interaction. The corresponding mechanisms are currently elucidated.

Ces rencontres francophones sur les légumineuses (RFL) sont co-organisées par l’Inra, le CIRAD, Terres Univia et Terres Inovia.Ces rencontres francophones sur les légumineuses (RFL) sont co-organisées par l’Inra, le CIRAD, Terres Univia et Terres Inovia.; Les légumineuses, qui contiennent des protéines de bonne qualité et peu couteuses en plus d’autres atouts nutritionnels, sont de bonnes candidates pour augmenter la part des protéines végétales dans notre diète et contribuer au développement de systèmes alimentaires durables. Cependant, des freins à leur utilisation (préparation longue, digestibilité difficile, …) ont conduit à une forte baisse de leur consommation. La fermentation est un moyen de diversifier l’offre d’aliments issus des légumineuses en augmentant leur digestibilité, voire leur valeur nutritionnelle. L’objectif du projet CoLeg était d’explorer la fermentescibilité de farines de différentes légumineuses par des communautés microbiennes voisines de celles rencontrées dans les produits laitiers fermentés : bactéries lactiques et bactéries et levures d'affinage du fromage. Trois légumineuses, pois jaune, soja et lupin blanc, ont été retenues pour ce projet. Des milieux de culture ont été développés à partir de suspensions de farines de ces 3 légumineuses à 10% dans l’eau, centrifugées et stérilisées pour répondre au mieux aux contraintes de chaque légumineuse. Les milieux ont ensuite été fermentés par cinq communautés microbiennes composées soit de bactéries lactiques mésophiles, soit de bactéries lactiques thermophiles, soit de microorganismes d'affinage du fromage, soit d’associations de ces différents groupes. Les milieux ont été caractérisés au cours de la fermentation par des analyses microbiologiques, biochimiques (pH, teneur en sucres résiduels, en acides organiques produits, en acides aminés libres, en protéines et en composés volatils) et par évaluation sensorielle (profil d’odeurs par la méthode Check-All-That-Apply). Les milieux préparés contenaient 22 à 30 g protéines par kg et 7 à 14 g de sucres fermentescibles par kg. Les deux principaux sucres sont le stachyose, un des oligosaccharides typiques de ces légumineuses, et le saccharose. Les communautés microbiennes ensemencées se sont toutes bien développées et atteignaient des populations finales de 108 à 109 unités formant colonies (UFC) par g pour les bactéries lactiques, de 108 UFC/g pour la bactérie d'affinage et de 106 à 107 UFC/g pour les levures. Dans les milieux fermentés par des bactéries lactiques, la consommation des sucres était concomitante avec la production d’acide lactique et le pH final était inférieur à 4.5, alors que le pH final était proche de 6 dans les milieux fermentés par des microorganismes d'affinage. Une protéolyse forte a été observée dans tous les milieux fermentés. De plus, au cours de la fermentation, les profils des sucres, des acides aminés libres et des composés volatils variaient significativement et étaient plus impactés par la communauté microbienne que par la légumineuse. Des différences sensorielles marquées ont été observées et dépendaient également principalement des communautés microbiennes. Par exemple, les milieux fermentés avec les bactéries lactiques étaient caractérisés par la présence de diacétyle et associés à des odeurs lactiques, alors que ceux fermentés avec les communautés d'affinage se distinguaient par des profils de composés volatils riches en esters, acides, et alcools et par des odeurs fruitées, piquantes et alcoolisées. Enfin, une diminution significative de composés tels que l’hexanal, associés aux notes « verte », « terreuse » indésirables des légumineuses a été observée dans tous les milieux fermentés.Ces premiers résultats montrent qu’il est possible d’implanter différentes communautés microbiennes sur des milieux préparés à partir de légumineuses et de générer des profils aromatiques très variés, offrant des perspectives de développement de nouveaux aliments fermentés à partir de légumineuses.

Ces rencontres francophones sur les légumineuses (RFL) sont co-organisées par l’Inra, le CIRAD, Terres Univia et Terres Inovia.Ces rencontres francophones sur les légumineuses (RFL) sont co-organisées par l’Inra, le CIRAD, Terres Univia et Terres Inovia.; Diversifier les sources alimentaires devient crucial dans un contexte de systèmes alimentaires durables1. La part des légumineuses, malgré leur fort taux protéique, a fortement décliné dans notre diète depuis 50 ans. Un moyen de les réintroduire est de les utiliser sous d’autres formes. Associer des protéines animales et végétales et les fermenter peut ainsi apporter des bénéfices supplémentaires, organoleptiques et nutritionnels aux légumineuses. Cependant, n’ayant aucun aliment fermenté de référence, rassembler dans des communautés bactériennes, des souches qui ne colonisent pas les mêmes habitats et dont on ne sait pas a priori si elles vont coopérer ou non, nécessite de revoir les concepts conduisant à former de nouvelles communautés.Objectif et Stratégie utilisésPour ce faire, nous avons utilisé des espèces de bactéries lactiques largement utilisées pour fermenter des ressources alimentaires variées. Nous avons choisi de concevoir ces communautés bactériennes sur la base de leur complémentarité métabolique, sur deux critères : la capacité des souches à fermenter les sucres et à hydrolyser les protéines des différentes ressources, dans le cas présent du lait bovin et de la farine de lupin. Notre stratégie a consisté à : i) sélectionner in silico des espèces de bactéries lactiques possédant les gènes impliqués dans le métabolisme des sucres ; ii) cribler in vitro un ensemble de souches capables d’utiliser les protéines et les sucres du lait et/ou du lupin et iii) concevoir des communautés composées de souches aux fonctions complémentaires.Principaux résultats obtenusL’étude in silico a permis via les données génomiques disponibles pour les souches de bactéries lactiques mésophiles homofermentaires, de rechercher trois enzymes, β-galactosidase, α-galactosidase et α-glucosidase, impliquées respectivement dans l’hydrolyse du lactose (lait), du raffinose et/ou du stachyose et du saccharose (lupin). Une fois les espèces bactériennes d’intérêt sélectionnées, le criblage in vitro a permis de confirmer pour chaque souche l’utilisation des sucres et de tester les activités protéolytiques globales sur les caséines et les protéines de lupin. Un «clustering» des souches a permis ensuite de regrouper les souches considérées comme « métaboliquement équivalentes » sur les critères choisis et de concevoir les communautés afin qu’elles expriment tous les critères, i.e. hydrolyse des sucres et des protéines. Les mixtes lait-lupin ont été fermentés par différentes souches de bactéries lactiques, lactocoques et lactobacilles, associées sous forme de communautés ou en culture pure afin d’estimer la plus-value des communautés. Les niveaux de populations bactériennes ont été évalués avant et après fermentation ainsi que le pH, la protéolyse globale, et les teneurs en sucres résiduels, en acides organiques, en acides aminés libres et en composés volatils.Nos résultats montrent que les populations bactériennes dans les communautés étaient en général plus élevées que dans les cultures pures. De façon cohérente, les milieux fermentés par les communautés avaient également un pH plus faible et une teneur plus élevée en acide lactique produit. De plus, les teneurs en sucres du lupin étaient diminuées, notamment celles du raffinose, du stachyose et du verbascose, sucres impliqués dans certains troubles digestifs. De même, la teneur en hexanal généralement associé à une flaveur indésirable était fortement réduite après fermentation. ConclusionIl est apparu que les souches coopéraient entre elles. Ainsi, les souches hydrolysant les protéines favorisaient la croissance des souches non protéolytiques, en leur fournissant peptides et acides aminés libres. Enfin, la fermentation des matrices mixtes a permis de moduler les cinétiques d’hydrolyse des protéines lors de la phase de digestion gastrique in vitro. Ces travaux illustrent une démarche de conception de communauté bactérienne qui peut être, transférable à d’autres matrices, mixtes ou non pour aider à diversifier les aliments fermentés à base de légumineuses.

International audience; Introduction Propionibacterium freudenreichii (PF) is a beneficial bacterium, used as Swiss-type cheeses starter. PF exerts several beneficial effects, including anti-inflammatory modulation. This feature relies on several metabolites and on surface proteins. PF emerges as a suitable candidate to develop fermented functional foods. As it is established, the probiotic properties are strain-dependent, however the delivery vehicle effect is barely explored. Aim In this study, our purpose is to explore how the cheese matrix impact its immunomodulatory properties on model of healthy piglets. Methods Three groups of weaned piglets were fed during 2 weeks with PF in form of a culture or of a fermented cheese and compared to a control group fed with sterile cheese. PF’s metabolic activity was assessed by short chain fatty acids dosage and microbiota modulation. Immune cells from small intestinal mesenteric nodes (MLNC) and blood (PBMC) were extracted. The basal cytokines secretion and T lymphocytes phenotypes were evaluated. Then, the immune cells were ex vivo stimulated by pro-inflammatory and anti-inflammatory stimuli and the cytokine response was determined. Results PF was metabolically active in piglets’ colon and enhanced bifidobacteria population and SCFAs production, without significant difference between the two delivery vehicles. PF decreased the secretion of TNFα and IL-10 secretion only by PBMC. In MLNC, PF cheese enhanced Treg and Th2 populations and sustained Th17 population. PF culture enhanced decreased Th17 population in MLNC. In PBMC, PF ingestion enhanced Treg and Th2 populations, without difference between the two delivery vehicles. Ex vivo stimulation of PBMC and MLNC showed a difference in immunomodulation of PF, according the delivery vehicle. Conclusion These results provide new insights into the cheese matrix effect on P. freudenreichii' probiotic functionalities. Such data showed the relevance to take in account the delivery vehicle to develop functionnal foods.

Probiotics already in your fridge?. 14.congrès national de la Société Française de Microbiologie (SFM)

Introduction Propionibacterium freudenreichii (PF) is a Swiss-type cheeses starter and has versatile probiotic properties due to various beneficial metabolites. PF recently emerged as a suitable candidate to develop fermented functional foods. Delivery of viable bacteria to the colon is crucial for in situ beneficial metabolites production. The delivery vehicle was shown to influence P. freudenreichii tolerance towards digestive stresses. It is also suggested to influence PF adaptation to the colon environment. In addition, during digestion, the delivery vehicle may prevent or allow proteolysis of surface proteins. These surface proteins are generally thought to contribute to bacteria tolerance towards environmental stresses. Aim This study aimed at evaluating PF (strain CIRM-BIA 129) adaptation to the caecal environment, according to the delivery vehicle. Besides, we evaluated PF survival in the caecal environment after removal of bacterial surface proteins by enzymatic proteolysis. We address the plausible role of S-layer protein SlpB in PF adaptation and survival. Methods Caecal medium was prepared from caecal contents recovered from piglets. PF pellets were harvested from cultures in Yeast Extract-Lactate (YEL), in Milk ultrafiltrate, or from cheese. Wild-type and SlpB KO mutant PF were further compared with respect to survival in caecal medium. Bacterial pellets were also submitted to surface proteins proteolysis to mimic digestion. Cultures were incubated 50 h at 37°C in anaerobiosis. Survival was monitored by plate counting, optical density and by live/dead fluorescence labeling. Results PF survival decreased in the caecal medium with a similar rate, whatever the growth medium tested. However, optical density was stable and the epifluorecence images did not show dead bacteria. Reduced survival rate was not due to significant cell death.PF seemed rather to enter a viable but nonculturable state in the caecal medium. Surprisingly, proteolytic removal of surface layer proteins enhanced PF culturable state in caecal medium. In addition, the mutation of SlpB did not change PF culturable state but surface proteins proteolysis enhanced also PF KO SlpB s culturable state. Conclusion These results indicate that surface proteins proteolysis during digestion may enhance PF survival and metabolic activity within the caecal medium. A comparative proteomic analysis will address the molecular mechanisms involved in enhanced survival.

IntroductionP. freudenreichii est utilisé comme ferment pour les fromages de type emmental et également comme probiotique. La stabilisation de P. freudenreichii sous forme de poudre est essentielle pour garantir une bonne stabilité. La lyophilisation et le séchage par atomisation peuvent être utilisés pour produire des ferments et des probiotiques en poudre. Le séchage par atomisation demande moins d’énergie que la lyophilisation. Cependant le séchage par atomisation expose les bactéries à de très hautes températures. Ce séchage est donc un procédé stressant, provocant des stress thermique, oxydatif et osmotique. En vue de résister à ce procédé, les bactéries doivent donc être adaptées. Les milieux de culture sont un moyen d’adapter les bactéries dans le but d’augmenter leur survie au séchage par atomisation.ObjectifDans cette étude, nous avons exploré l’influence de la composition du milieu de culture sur 1) l’accumulation d’osmoprotecteurs et 2) la survie des bactéries lors du séchage par atomisation.Matériels et méthodesPour le milieux riche YEL (Yeast Exctract Lactate) et les milieux laitiers, les concentrations de sel les plus élevées permettant la croissance de P. freudenreichii ont été choisies. Les osmoprotecteurs accumulés par P. freudenreichii ont été identifiés et quantifiés par RMN du proton et du carbone. Les différentes cultures ont ensuite subi les challenges oxydatifs, thermique et le séchage par atomisation.RésultatsPendant la croissance, P. feudenreichii CIRM-BIA 129 accumulent du tréhalose, du glutamate et de la glycine betaine. En condition hyper osmotique, l’accumulation de ces osmoprotecteurs est plus élevés. Le lactose naturellement présent dans le lactosérum, ou ajouté dans le YEL, provoque une adaptation au stress acide, mais augmente également l’accumulation intracellulaire du tréhalose. Le ratio tréhalose/glycine betaine accumulés est déterminé par le ratio azote/carbone du milieu de culture. Avec un ratio tréhalose/glycine betaine optimisé, P. freudenreihcii a une meilleure survie au challenge thermique et oxydatif, comme au séchage par atomisation.ConclusionPiloter la composition du milieu de culture de P. freudenreichii permet de diriger l’adaptation et conduit à une meilleure survie durant le séchage par atomisation. Ceci permettra par la suite la production de qualité des ferments et probiotiques avec de hauts rendement.