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The Citrate Metabolism in Homo-and Heterofermentative LAB:A Selective Means of Becoming Dominant over Other Microorganisms in Complex Ecosystems

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Food and Nutrition Sciences 2014年第10期5卷 953-969页

作者： Gemelas Laetitia Degraeve Pascal demarigny yann Isara-Lyon AgrapoleFood Microbiology LaboratoryBIODYMIALyonFrance Lyon 1 University Research Laboratory in Industrial Engineering Food—BIODYMIA EA 373Bourg-en-BresseFrance

The citrate metabolism has been extensively studied in lactic acid bacteria (LAB) for its aroma compound production. Among the 4-carbon (C4) by-products obtained from citrate fermentation, diacetyl is one of the better known products for its contribution to the buttery aroma of dairy products. A lot of documents deal with ways to improve diacetyl concentration in food matrices. Apart from these organoleptic advantages, in a microbial ecosystem, the citrate metabolism gives selective advantages to citrate positive microorganisms. Citrate metabolism allows the LAB to use another carbon source for their growth, withstand acidic conditions and generate a “proton motive force” (PMF). Moreover, the citrate/glucid co-metabolism leads to the fast release of organic compounds known for having bacteriostatic effects. Under specific conditions, the C4?pathway liberates diacetyl which is bacteriostatic. In this review we first describe the citrate metabolism and the enzymes involved in the two homo- and heterofermentative LABLc diacetylactisandLeuconostocspp. Moreover, the way to shift the metabolic pathway toward the production of aromatic compounds is discussed for both of these fermentative types of bacteria. Finally, the selective advantages of citrate metabolism for LAB in complex microbial ecosystems are delineated.

关键词： Citrate Metabolism Lactococcus lactis subsp.lactis biovar.diacetylactis Leuconostoc spp. Complex Microbial Ecosystems Homo-and Heterofermentative Lactic Acid Bacteria

Use of <i>Lactococcus lactis</i>Subsp. <i>Lactis</i>Strains to Inhibit the Development of Pathogens

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Food and Nutrition Sciences 2020年第2期11卷 98-112页

作者： Abir Maalaoui Abdesselem Trimeche Pierre Guy Marnet yann demarigny Institut Supérieur Agronomique de Chott Mariem Université de Sousse Sousse Tunisie Laboratoire de gestion de la santé et de la qualité des productions animales Ecole Nationale de Médecine Vétérinaire de Sidi Thabet Université de La Manouba Manouba Department of Animal Science and Production AGROCAMPUS OUEST Rennes France Bioengineering and Microbial Dynamic at Food Interfaces (Associated team n°3733 (BioDyMIA) University of Lyon 1-ISARA Lyon) Isara-Lyon Agrapole-23 rue Jean Baldassini F-69364 Lyon Cedex 07 France

Bovine mastitis affects the udder health and thus causing significant economic losses. Probiotic products based on the use of lactic acid bacteria (LAB) to limit pathogens multiplication and pre-infection risks can be an interesting alternative to post infection allopathic treatment with antibiotics. Lactococcus lactis is one of the most important bacteria used in dairy technology. In this work, a total of 21 Lactococcus lactis subsp. Lactis strains, 20 from goat milk whey and one strain from cow milk were used to evaluate their antibacterial activity against four pathogenic germs responsible for mastitis: Escherichia coli, Staphylococcus aureus, Streptococcus uberis and Streptococcus agalactiae. The nisin-producing cow milk strain was active against St. uberis and Str. Agalactiae using the well diffusion method. For the strains isolated from goat milk whey, no antimicrobial effect was observed against these pathogens. However, a different approach based on the growth of pathogenic bacteria interacting with the Lactococcus lactis strains in a minimum medium was used to study the barrier effect of LAB. The Lactococcus lactis strains S1 and S2 from goat milk whey depleted the growth of Sa. aureus, St. uberis and E. coli during 8 h and stopped the development of St. agalactiae.

关键词： Lactococcus lactis Minimal Medium Pathogenic Bacteria Antibacterial Activity Barrier Effect

A Rapid Electrophoresis Method on Agarose Gel to Characterise Dairy Protein Aggregates

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Food and Nutrition Sciences 2018年第4期9卷 325-334页

作者： Laetitia Gemelas Pascal Degraeve Marion Morand Arnaud Hallier yann demarigny Univ Lyon ISARA Lyon Université Lyon 1 BioDyMIA (Bioingénierie et Dynamique Microbienne aux Interfaces Alimentaires) EA n&#176 3733 ISARA Agrap&#244 le Lyon France Univ Lyon Université Lyon 1 ISARA Lyon BioDyMIA (Bioingénierie et Dynamique Microbienne aux Interfaces Alimentaires) EA n&#176 3733 IUT Lyon 1 technopole Alimentec rue Henri de Boissieu BOURG-EN-BRESSE France General Mills Inc One Global Dairy Vienne Technical Center Chemin des Mines Vienne France ISARA Lyon Chemistry Laboratory Lyon France

Heat treatment of milk may cause whey proteins and caseins to form aggregates. These soluble and micellar aggregates and their other properties (size, composition, shape, etc.) can affect the techno-functionalities to the milk, conferring interesting or negative features depending on the application in dairy industries. In this study, we propose a new approach to characterise those protein aggregates. SDS-agarose electrophoresis is followed by the calculation of a retention factor (Rf) for each protein spot. Rf allows milk aggregates to be compared qualitatively under the same conditions. This method could be transposed to the dairy industry for a better knowledge of the milk subsequent to heat treatment.

关键词： Heat Treatment of Milk Dairy Protein Aggregates Agarose Gel Electrophoresis

Selective Lactococcus Enumeration in Raw Milk

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Food and Nutrition Sciences 2013年第9期4卷 49-58页

作者： Laetitia Gemelas Véronique Rigobello Mai Huong Ly-Chatain yann demarigny Isara-Lyon Unité BioDyMIALyonFrance

The Lactococcus diversity in cow and goat raw milk was investigated. To do so, a protocol had to be established for the specific enumeration of lactococci. Eight agar media and one control medium were analysed to compare their proficiency in evaluating the Lactococcus population in raw milk: M17 Nal, Elliker, modified Elliker, PCA + milk, modified KCA, modified Chalmers, Turner, FSDA. The M17 medium was used as reference. Eighteen pure strains were tested on these media for their selectivity towards lactococci: six Lactococcus species or subspecies, three Leuconostoc, three Enterococcus, two Lactobacillus, one Streptococcus thermophilus, one Pseudomonas fluorescens, one Escherichia coli and one Staphylococcus aureus. All these bacteria were chosen for their regular presence in raw milk. The KCA medium proved to be the most selective towards lactococci, on condition that 1) we discriminated the colonies using the catalase test and 2) we subtracted the Enterococcus population counted on BEA. However, it was not possible to separate the Streptococcus from the Lactococcus colonies on KCA. The “Lactococcus-like” population including these two genera was estimated at a mean level of 3.18 log(cfu)/mL and 4.14 log(cfu)/mL in cow and goat raw milk respectively. This is consistent with the data already published.

关键词： Lactococcus Culture Media Raw Milk LAB Modified KCA

Utilisation of a Portable Electronic Nose, NeOse Pro, to Follow the Microbial Fermentation of a Yoghurt

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Food and Nutrition Sciences 2021年第1期12卷 90-105页

作者： yann demarigny Elodie Legrand Julia Sanchez Arnaud Hallier Nathalie Laurent Sami Slimani Thierry Livache Daniel Picque ISARA Lyon Equipe AgroLab BioDyMIA (Bioingénierie et Dynamique Microbienne aux Interfaces Alimentaires) ISARA Agrap&#244 le Lyon France Aryballe Technology Grenoble France INRA GMPA AgroParis Tech Paris France

Yoghurt is fermented milk which results from the exclusive action of Lactobacillus delbrueckii subsp bulgaricus and Streptococcus thermophilus. However, a disruption of the bacterial growth can lead to significant industrial losses. Currents monitoring methods, based on the checking of the pH during the fermentation step are not always satisfactory. The NeOse Pro system, a portable electronic nose, is a mean to obtain immediately aromatic profiles. In this work, we applied this technology to the yoghurt ecosystem, a highly hydrated product. The profiles obtained allowed us to discriminate yoghurts before and after fermentation. In detail, the discrepancy between the two bacteria cultured alone was slight. It was also the case when we compared different initial bacterial ratios. However, two different mixes of bacteria led to clearly distinguishable profiles. A GC/MS analysis performed on products fermented 7 h allowed us to explain the detection of acetaldehyde by the stimulation of some captors of the apparatus. NeOse Pro is so convenient to study the fermentation of yogurt.

关键词： NeOse Pro Yoghurt GC/MS Aroma

Influence of the Backslopping Practice on the Microbial Diversity of the Lactococcus Population in a Model Cheesemaking

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Food and Nutrition Sciences 2011年第6期2卷 618-627页

作者： yann demarigny Marion Dalmasso Aline Tonleu Véronique Rigobello Eric Beuvier Mai Huong Ly-Chatain Yvette Bouton Isara-Lyon AgrapoleLaboratoire de microbiologie alimentaireLyonFrance INRA-UR342 Technologie et Analyses Laitières PolignyFrance ComitéInterprofessionnel du Gruyère de Comté R&D Unit PolignyFrance

The objective of this work was to study the microbial diversity of natural whey starters (NWS), with a special focus on Lactococcus strains, during 10 successive days of backslopping. Each day, whey samples were enumerated for their Lactococcus, Enterococcus, Leuconostoc and Lactobacillus levels. The diversity and dynamics of the Lactococcus population in whey were investigated using phenotypic methods such as acidifying aptitude and enzymatic activities. Molecular approach using REP-PCR, ERIC-PCR, plamid profiles, phages and prophages research and PFGE was also applied. Lactococci were the main population in whey. Strains from raw milk were sub-dominant. Based on PFGE and phenotypic results lactococci in whey displayed a more heterogeneous phenotype and pulsotype which may reflect greater variations than previously observed within starter. No phages and prophages were spotted on. Plasmids did not seem to be exchanged from strain to strain. The backslopping practice seemed to allow the strains of the starter to rapidly acquire a specificity of their own. The changes observed presumed a slow adaptation of the strains to the “back- slopping environment”. The study of NWS diversity constitutes an important step for the comprehension of acidification defects that recurrently occur in cheesemaking technologies using the backslopping practice.

关键词： Backslopping Natural Whey Starter Model Cheesemaking Lactococcus

Influence of the Backslopping Practice on the Microbial Diversity of the Lactococcus Population in a Model Cheesemaking

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Utilisation of a Portable Electronic Nose, NeOse Pro, to Follow the Microbial Fermentation of a Yoghurt

Food and Nutrition Sciences 2011年第6期

作者： yann demarigny Marion Dalmasso Aline Tonleu Véronique Rigobello Eric Beuvier Maï Huong Ly-Chatain Yvette Bouton

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