The Experts below are selected from a list of 14934 Experts worldwide ranked by ideXlab platform
Bo Lonnerdal - One of the best experts on this subject based on the ideXlab platform.
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bioactive proteins in human milk health nutrition and implications for infant formulas
The Journal of Pediatrics, 2016Co-Authors: Bo LonnerdalAbstract:Breast milk confers many benefits to the newborn and developing infant. There is substantial support for better long-term outcomes, such as less obesity, diabetes, and cardiovascular disease, in breastfed compared with formula-fed infants. More short-term outcomes, such as incidence and duration of illness, nutrient status, and cognitive development during the first year of life also demonstrate benefits of breastfeeding. Several proteins in breast milk, including lactoferrin, α-lactalbumin, milk fat globule membrane proteins, and osteopontin, have been shown to have bioactivities that range from involvement in the protection against infection to the acquisition of nutrients from breast milk. In some cases, bovine counterparts of these proteins exert similar bioactivities. It is possible by Dairy Technology to add protein fractions highly enriched in these proteins to infant formula.
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clinical benefits of milk fat globule membranes for infants and children
The Journal of Pediatrics, 2016Co-Authors: Olle Hernell, Niklas Timby, Magnus Domellof, Bo LonnerdalAbstract:The milk fat globule membrane (MFGM) in breast milk contains many bioactive components. Infant formulas traditionally have been devoid of the MFGM fraction, but Dairy Technology now has made the addition of bovine MFGM technically feasible. We identified 6 double-blinded randomized controlled trials exploring the effects of MFGM supplementation on the diets of infants or children. Results suggest that supplementation is safe and indicate positive effects on both neurodevelopment and defense against infections. MFGM supplementation of infant formula may narrow the gap in cognitive performance and infection rates between breastfed and formula-fed infants. Because of the small number of studies and the heterogeneity of interventions, more high-quality double-blinded randomized controlled trials are needed, with well characterized and clearly defined MFGM fractions, before firm conclusions on the effects of MFGM supplementation on the health and development of infants can be drawn.
Véronique Monnet - One of the best experts on this subject based on the ideXlab platform.
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Complete Genome Sequence of the Industrial Fast-Acidifying Strain Streptococcus thermophilus N4L.
Microbiology Resource Announcements, 2018Co-Authors: Lucas Proust, Valentin Loux, Véronique Martin, Cristian Magnabosco, Martin Bo Uhre Pedersen, Véronique Monnet, Vincent JuillardAbstract:ABSTRACT Streptococcus thermophilus is one of the most used Dairy starters for the production of yogurt and cheese. We report here the complete genome sequence of the industrial strain S. thermophilus N4L, which is used in Dairy Technology for its fast-acidifying phenotype.
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the oligopeptide transport system is essential for the development of natural competence in streptococcus thermophilus strain lmd 9
Journal of Bacteriology, 2009Co-Authors: Rozenn Gardan, Colette Besset, Alain Guillot, Christophe Gitton, Véronique MonnetAbstract:In gram-positive bacteria, oligopeptide transport systems, called Opp or Ami, play a role in nutrition but are also involved in the internalization of signaling peptides that take part in the functioning of quorum-sensing pathways. Our objective was to reveal functions that are controlled by Ami via quorum-sensing mechanisms in Streptococcus thermophilus, a nonpathogenic bacterium widely used in Dairy Technology in association with other bacteria. Using a label-free proteomic approach combining one-dimensional electrophoresis with liquid chromatography-tandem mass spectrometry analysis, we compared the proteome of the S. thermophilus LMD-9 to that of a mutant deleted for the subunits C, D, and E of the ami operon. Both strains were grown in a chemically defined medium (CDM) without peptides. We focused our attention on proteins that were no more detected in the ami deletion mutant. In addition to the three subunits of the Ami transporter, 17 proteins fulfilled this criterion and, among them, 7 were similar to proteins that have been identified as essential for transformation in S. pneumoniae. These results led us to find a condition of growth, the early exponential state in CDM, that allows natural transformation in S. thermophilus LMD-9 to turn on spontaneously. Cells were not competent in M17 rich medium. Furthermore, we demonstrated that the Ami transporter controls the triggering of the competence state through the control of the transcription of comX, itself controlling the transcription of late competence genes. We also showed that one of the two oligopeptide-binding proteins of strain LMD-9 plays the predominant role in the control of competence.
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Control of the transcription of a short gene encoding a cyclic peptide in Streptococcus thermophilus: a new quorum-sensing system?
Journal of Bacteriology, 2007Co-Authors: Mariam Ibrahim, Alain Guillot, Françoise Wessner, Florence Algaron, Colette Besset, Pascal Courtin, Rozenn Gardan, Véronique MonnetAbstract:Gram-positive bacteria secrete a variety of peptides that are often subjected to posttranslational modifications and that are either antimicrobials or pheromones involved in bacterial communication. Our objective was to identify peptides secreted by Streptococcus thermophilus, a nonpathogenic bacterium widely used in Dairy Technology in association with other bacteria, and to understand their potential roles in cell-cell communication. Using reverse-phase liquid chromatography, mass spectrometry, and Edman sequencing, we analyzed the culture supernatants of three S. thermophilus strains (CNRZ1066, LMG18311, and LMD-9) grown in a medium containing no peptides. We identified several peptides in the culture supernatants, some of them found with the three strains while others were specific to the LMD-9 strain. We focused our study on a new modified peptide secreted by S. thermophilus LMD-9 and designated Pep1357C. This peptide contains 9 amino acids and lost 2 Da in a posttranslational modification, most probably a dehydrogenation, leading to a linkage between the Lys2 and Trp6 residues. Production of Pep1357C and transcription of its encoding gene depend on both the medium composition and the growth phase. Furthermore, we demonstrated that transcription of the gene coding for Pep1357C is drastically decreased in mutants inactivated for the synthesis of a short hydrophobic peptide, a transcriptional regulator, or the oligopeptide transport system. Taken together, our results led us to deduce that the transcription of the Pep1357C-encoding gene is controlled by a new quorum-sensing system.
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La biosynthèse des acides aminés à chaîne branchée et des purines : deux voies essentielles pour une croissance optimale de Streptococcus thermophilus dans le lait
Le Lait, 2001Co-Authors: Peggy Garault, Vincent Juillard, Catherine Letort, Véronique MonnetAbstract:Branched-chain amino acids and purine biosynthesis: two pathways essential for optimal growth of Streptococcus thermophilus in milk. Slowing down and delays in Streptococcus thermophilus growth in milk have negative effects for Dairy Technology. Our objectives are to understand the reasons for those delays, and to identify some of the functions essential for optimal growth of S. thermophilus in milk. To reach this goal, a random insertional mutagenesis was performed on a S. thermophilus strain chosen for its ability to grow rapidly in milk. We obtained 14 different mutants, affected in their capacity to grow quickly in milk. Four of them were further characterized: two were mutated in the branched-chain amino acids biosynthesis operon and two others were mutated in the purine nucleotides biosynthesis operon. Consequently, branched-chain amino acids and purine biosynthesis pathways are functional in S. thermophilus. Our results suggested that the amount of both branched-chain amino acids and purine nucleotides, present in milk, and directly consumable is not sufficient for an optimal growth. Moreover, we identified the branched-chain amino acids and purine biosynthesis pathways as essential functions for optimal growth of S. thermophilus in milk.
Christelle Lopez - One of the best experts on this subject based on the ideXlab platform.
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The milk fat globules: unique biological systems with a specific composition and multiscale organisation of lipids
2018Co-Authors: Christelle LopezAbstract:Increasing knowledge about the composition and biophysical properties of milk lipids is essential to better understand, modulate and control their properties in food products, to developinnovative functional foods but also to tailor specific lipid structures able to provide nutritional and health benefits. Milk lipids are an important source of energy and bioactive molecules for the optimal growth and development of breast-fed newborns. They are also involved in the functional properties and sensory quality of many Dairy products that are consumed by adults[1]. Milk is a natural O/W emulsion in whichfat globules are highly complex and unique entities as regard to the wide diversity of lipid molecules (98% triacylglycerols withmore than 400 fatty acids characterized byvarious chain length and saturation; polar lipidscontaining 30% sphingomyelin, cholesterol) and the multiscale organization of lipids (mean diameter of fat globules 4 µm; crystals of TAG; trilayer of polar lipids in the biological membrane).The structure of milk lipids, both TAG and polar lipids, is affected by temperature and thermal kinetics that induce phase transitions. Dairy processingalso have a major impact on the structure of milk lipids, with consequences on their reactivity in complex Dairy products, mainly interactions with milk proteins[1].Thelecturewill provide an overview of the specificities of milk fat globules in terms of composition, structure and functions.Moreover, the recent advances about the structure of the milk fat globule membrane including the dynamics of the lipid domainsrich in sphingomyelin and cholesterol that are responsible for topographical and mechanical heterogeneities will be presented [2,3,4]. The development of processed emulsion droplets bio-inspired by milk fat globules to improve the structure of lipids in infant formulas and narrow the gap with human milk will also be described [5].These recent and new findingswill undoubtadelyopen perspectives in Dairy Technology and human nutrition(infants and adults).
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Lipid domains in the biological membrane surrounding milk fat globules: role of temperature and cholesterol on their morphology and nanomechanical properties
2017Co-Authors: Christelle Lopez, Oumaima Et Thakafy, Venkata Ramana Murthy Appala, Fanny Guyomarc'hAbstract:The biological membrane surrounding fat globules in milk, the MFGM, is poorly known despite its importance in the functional properties of many Dairy products and in the mechanisms of milk lipids digestion occurring in the gastrointestinal tract of mammal newborns. Studies recently revealed the formation of lipid domains in the MFGM that have been interpreted as the lateral segregation of high phase transition temperature (Tm) lipids, mainly milk sphingomyelin (MSM; Tm 34°C) [1]. The role played by these MSM-rich domains in the MFGM is currently unknown and needs further investigation. In this context, the aim of this study was to investigate the role of temperature and cholesterol in the morphology and nanomechanical properties of the MFGM. Accessing the biophysical properties of biological membranes at nanoscale is possible using Atomic Force Microscopy (AFM). In the complex biomimetic membranes formed using a MFGM lipid extract, topographical AFM images revealed for T < 35°C the formation of µm-large domains that protruded above the continuous phase by ~1 nm [2]. The resistance of the MSM-rich gel phase domains to rupture was significantly higher than that of the liquid disordered continuous phase, i.e. breakthrough force FB of 23 nN vs. 6 nN at 25°C, respectively. The key role played by cholesterol in the lateral segregation of high Tm lipids, by decreasing the size of the lipid domains, their height and by fluidizing the MFGM has been demonstrated [3]. Such work on the heterogeneous distribution of polar lipids in the MFGM may open perspectives in Dairy Technology and infant nutrition, e.g. optimisation of the interface of processed lipid droplets in infant milk formulas to mimick the biological MFGM in breast milk.
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The MFGM and milk polar lipids: Highly reactive assemblies involving structural and mechanical heterogeneities
2016Co-Authors: Christelle Lopez, Chantal Cauty, Oumaima Et Thakafy, Venkata Ramana Murthy Appala, Fanny Guyomarc'hAbstract:Introduction The biological membrane surrounding fat globules in milk, i.e. the milk fat globule membrane (MFGM), is a trilayer assembly of polar lipids including 25-40% of sphingomyelin (SM) and glycerophospholipids. It is involved in the mechanical stability of fat globules, in the mechanisms of their digestion, and in physiological functions that need to be further understood. Increasing knowledge about the MFGM is therefore of primary importance both for Dairy Technology and nutrition. Aim The objectives of this study were to explore the dynamics of the MFGM polar lipids in situ in milk and to describe the biophysical properties of milk polar lipids assemblies as a function of temperature and composition, e.g. presence of cholesterol. Methods The biophysical properties and organization of polar lipids in the MFGM were investigated by the combination of techniques: DSC, synchrotron radiation XRD, CLSM, electron microscopy, AFM imaging and force spectroscopy. Results The MFGM is a dynamic patchwork exhibiting phase separation of the high melting temperature (Tm) polar lipids, mainly SM, to form domains in ordered phase dispersed in a continuous fluid phase composed of the unsaturated polar lipids. In absence of cholesterol, the SM-rich domains are formed for T < 35°C and can melt upon heating. These domains protrude by 1 nm and have a higher resistance to rupture than the fluid phase composed of the unsaturated polar lipids. When present, cholesterol exhibits attractive interactions with SM with a condensing effect, and affects the topography of the membrane with a fluidizing effect. Conclusion We propose an updated model for the heterogeneous organization of polar lipids in the MFGM, highlighting the dynamic changes in the topography and nanomechanical properties that are governed by the temperature and the presence of cholesterol. These recent findings on the assemblies of polar lipids in the MFGM and specific biophysical properties of SM in interaction with cholesterol will undoubtedly contribute in the development of smart biomimetic fat globules, e.g. in infant milk formulas.
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Lipid domains in the biological membrane surrounding milk fat globules: role of cholesterol on their morphology and nanomechanical properties, probed by AFM and force spectroscopy.
2015Co-Authors: Venkata Ramana Murthy Appala, Fanny Guyomarc'h, Shan Zou, Maohui Chen, Christelle LopezAbstract:a) Introduction. The biological membrane surrounding fat globules in milk is poorly known despite its importance in the functional properties of many Dairy products and in the mechanisms of milk lipids digestion occurring in the gastrointestinal tract of mammal newborns. The milk fat globule membrane (MFGM) is essentially composed of polar lipids (of which 30% is milk sphingomyelin; SMmilk), cholesterol and membrane proteins. Studies recently revealed the heterogeneous distribution of polar lipids in the outer bilayer of the MFGM that has been interpreted as the lateral segregation of high phase transition temperature (Tm) lipids, mainly SMmilk, in the form of “lipid rafts” at the surface of the milk fat globule (Lopez et al., 2010). In cells, “raft” structures composed by SM and cholesterol have been associated in signaling and trafficking biological mechanisms. The role played by these SMmilk-rich domains in the MFGM is currently unknown and needs further investigation. Accessing the biophysical properties of biological membranes at nanoscale is possible using Atomic Force Microscopy (AFM) and could provide a better insight into the heterogeneous distribution of lipids and in the nanomechanichal properties of the MFGM. In this context, the aim of this study was to investigate the role of cholesterol in the morphology and nanomechanical properties of the MFGM. b) Materials & methods. Lipid films containing i) SMmilk/DOPC (50/50%mol), ii) SMmilk/DOPC/chol (40/40/20%mol), or iii) a complex MFGM lipid extract with 0 or 50 % mol. of cholesterol to the SMmilk were prepared in chloroform/methanol and evaporated under N2. The lipid films were then hydrated at T=60°C > Tm of SMmilk, at 1mg/mL in PIPES buffer pH 6.7 containing 2 mM Ca2+. Small unilamellar vesicles were obtained by sonication then fused onto freshly cleaved mica in PIPES buffer and at 60°C to form hydrated lipid bilayers, which were further cooled to room temperature in a programmed incubator to control the formation of lipid domains. Imaging and force spectroscopy experiments were conducted with an MFP-3D Asylum Research AFM in PIPES buffer and at room temperature. c) Results & discussions. In model membranes composed by SMmilk and DOPC, the lateral segregation of SMmilk to form 0.9 nm-salient and µm-wide domains was observed for T < 35°C, which corresponds to the liquid crystalline to gel phase transition temperature of SMmilk (Tm 34°C). These domains were interpreted as segregated high Tm lipids in the gel phase surrounded by a continuous fluid phase. In the presence of cholesterol, the SMmilk domains were scattered into numerous shorter, smaller, tortuous individuals and were less resistant to rupture than in absence of cholesterol, indicating a tendency to mixing into the continuous fluid phase (Guyomarc’h et al., 2014). In the complex biomimetic membranes formed using a MFGM lipid extract, topographical AFM images showed that in the absence of added cholesterol (Figure 1, top left), µm-large domains were formed that protruded above the continuous phase by ~1 nm. In the presence of cholesterol (Fig. 1, bottom left), scattered nm-sized domains were characterised. On the same locations, AFM force spectroscopy experiments were performed to estimate the mechanical strength of the bilayers. Without cholesterol (Fig 1, top row), the fluid phase ruptured at ~5 nN while the domains could not be pierced by the AFM tip at the 12 nN force load set point (black pixels in the force maps). This indicated higher stiffness of these domains than in model SMmilk domains (Guyomarc’h et al., 2014), possibly due to traces of ceramides (Sullan et al., 2009). In the presence of cholesterol the breakthrough force was less (~3 nN) and more homogeneous across the milk lipid membranes, i.e., the domains were softer than in absence of cholesterol. The results are interpreted in terms of the fluidizing effect of the cholesterol onto SM (Simons and Vaz, 2004). In conclusion, cholesterol plays a key role in the lateral segregation of high Tm lipids in the biological membrane surrounding milk fat globules, by decreasing the size of the lipid domains, their height and by fluidizing the MFGM. Such work on the heterogeneous distribution of lipids in the MFGM may open perspectives in Dairy Technology and infant nutrition (e.g. optimisation of the interface of processed lipid droplets in infant formulas as compared to the biological MFGM in breast milk).
Sylvie Lortal - One of the best experts on this subject based on the ideXlab platform.
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Wooden tools: a reservoir of microbial biodiversity in traditional cheese making
2014Co-Authors: Sylvie Lortal, Giuseppe. Licitra, Florence Valence-bertelAbstract:Wood is a natural and sustainable material which has been used for centuries in traditional cheese production in a wide variety of forms (vats, shelves, packaging). It is an “alive” actor in the cheese making process, interacting with the milk in the vats or with the cheeses placed on the shelves for ripening. Wood is alive due to its ability to exchange water but, above all, because it is covered by a rich microbial biofilm. As wood is porous and difficult to clean, the European Commission regularly highlights the question of its safety when in contact with food and strongly requests deeper scientific investigation. In this review, knowledge about the multiple technological roles of wood in Dairy Technology, in particular its crucial role as reservoir of microbial biodiversity for traditional cheeses, as well as the results of safety assessments, will be presented. As a conclusion, the numerous questions remaining about this natural inoculating system will be discussed.
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Wooden Tools: Reservoirs of Microbial Biodiversity in Traditional Cheesemaking
2014Co-Authors: Sylvie Lortal, Giuseppe. Licitra, Florence Valence-bertelAbstract:Today, wooden shelves are used for the ripening of about 500,000 tons of cheese per year in Europe, including about 350,000 tons in France, such as most of the famous cheeses with the protected designation of origin (PDO), e.g., Comté, Reblochon, Beaufort, Munster, Cantal, and Roquefort. For some PDO cheeses, the use of wooden tools is mandatory.Many cheesemakers believe that wooden tools improve the organoleptic and typical characteristics of their final products. Wood is a natural and sustainable material which has been used for centuries in traditional cheese production in a wide variety of forms (vats, shelves, and packaging). Wood is important in the cheesemaking process, interacting with the milk in vats or with the cheeses placed on shelves for ripening. Wood is viable due to its ability to exchange water but, above all, because it is covered by a rich microbial biofilm. As wood is porous and difficult to clean, the European Commission regularly highlights the question of its safety when in contact with food and calls for deeper scientific investigation. In this review, knowledge about the multiple technological roles of wood in Dairy Technology is discussed. The crucial role of wood as a reservoir of microbialbiodiversity for traditional cheeses is reviewed, along with results of safety assessments. As a conclusion, the numerous questions remaining about this natural inoculating system are discussed.
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Efficient mechanical disruption of Lactobacillus helveticus, Lactococcus lactis and Propionibacterium freudenreichii by a new high-pressure homogenizer and recovery of intracellular aminotransferase activity
Journal of Industrial Microbiology and Biotechnology, 2003Co-Authors: L.v. Saboya, Marie-bernadette Maillard, Sylvie LortalAbstract:Microbiological studies often involve bacterial cell fractionation, which is known to be difficult for Gram-positive as compared to Gram-negative bacteria. Our purpose was to test the breaking efficiency of a new high-pressure pilot homogenizer for three Gram-positive species involved in Dairy Technology and to assess the activity of an intracellular aminotransferase. Varied pressures (50, 100 and 200MPa) were applied to concentrated bacterial suspensions (1.2mg dry weight/ ml) of Lactobacillus helveticus, Lactococcus lactis and Propionibacterium freudenreichii. Breaking efficiency was estimated by decreases in optical density at 650nm, cellular dry weight and viability. The proteins released were quantified and the residual intracellular aminotransferase activity was estimated using leucine as substrate. One run at 50MPa was sufficient to break 80% of lactobacilli cells whereas 200MPa were required for the same efficiency for L. lactis and P. freudenreichii. Whatever the pressure, leucine aminotransferase activity was recovered in the supernatant after cell breaking. This new high-pressure pilot homogenizer can allow rapid (20s/run), easy, continuous and highly efficient cell breaking for intracellular enzyme recovery or other purposes. As the species tested were not phylogenetically related, and had different morphologies and cell wall compositions, we conclude that most Gram-positive bacteria may be broken efficiently by this new device.
Catherine Denis - One of the best experts on this subject based on the ideXlab platform.
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Somatic cell recovery by microfiltration technologies: A novel strategy to study the actual impact of somatic cells on cheese matrix
International Dairy Journal, 2017Co-Authors: Na Li, Romain Richoux, Nadine Leconte, Claudia Bevilacqua, Marie-bernadette Maillard, Sandrine Parayre, Lydie Aubert-frogerais, Jessica Warlouzel, Elisabeth Moya-leclair, Catherine DenisAbstract:Abstract The actual impact of the somatic cells in the Dairy Technology is still ill-defined, because the increase in milk somatic cell count, usually correlated with mastitis factors, impairs the raw milk composition, through mainly unwanted proteolysis and lipolysis. This study used microfiltration technologies for recovering high quantity of somatic cells and for clarifying their role in cheese quality. Three series of Swiss-type cheeses were manufactured by adding 0 (control), 4 × 105 and 9 × 105 somatic cells mL−1. These cells were traced for the first time during the cheese making process by using adapted flow cytometry and real-time quantitative PCR. Proteolysis and lipolysis indices were measured throughout ripening time. Only a weak increase in lipolysis (+28%) and proteolysis (+8%) was observed in the highest somatic cell count cheese, despite 73% of the cells trapped within the cheeses. Our approach gives a new view of somatic cell role in cheese milk alteration.
