Sophie Jan

Sophie Jan
Agrocampus Ouest · Department of Animal and Food Sciences

habilitation

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92
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Introduction
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Publications

Publications (92)
Article
Full-text available
The Bacillus cereus (B. cereus) group is a widespread foodborne pathogen with a persistent ability to form biofilm, and with inherent resistance to traditional treatment in the food industry. Bacteriophages are a promising biocontrol agent that could be applied to prevent or eliminate biofilms formation. We have described, in this study, the isolat...
Article
Full-text available
Eggs are a whole food which affordably support human nutritional requirements worldwide. Eggs strongly resist bacterial infection due to an arsenal of defensive systems, many of which reside in the egg white. However, despite improved control of egg production and distribution, eggs remain a vehicle for foodborne transmission of Salmonella enterica...
Article
A recent work revealed that egg white (EW) at 45 °C exhibits powerful bactericidal activity against S. enterica serovar Enteritidis, which is surprisingly little affected by removal of the >10 kDa EW proteins. Here, we sought to identify the major EW factors responsible for this bactericidal activity by fractionating EW using ultrafiltration and na...
Article
Full-text available
Salmonella enterica serovar Enteritidis is noted for its ability to survive the harsh antibacterial activity of egg white which is presumed to explain its occurrence as the major food-borne pathogen associated with the consumption of eggs and egg products. Liquid egg white is a major ingredient for the food industry but, because of its thermal frag...
Article
Full-text available
Salmonella Enteritidis is the most prevalent food-borne pathogen associated with egg-related outbreaks in the European Union. During egg colonization, S. Enteritidis must resist the powerful anti-bacterial activities of egg white (EW) and overcome ovotransferrin-imposed iron-restriction (the most important anti-bacterial mechanism of EW). Many path...
Article
The famous French dessert "ile flottante" consists of a sweet egg white foam floating on a vanilla custard cream, which contains highly nutritive raw materials, including milk, sugar and egg. Spoilage issues are therefore a key concern for the manufacturers. This study explored the bacterial diversity of 64 spoiled custard cream desserts manufactur...
Article
Full-text available
Background: Despite the importance of the B. cereus group as major foodborne pathogens that may cause diarrheal and/or emetic syndrome(s), no study in Tunisia has been conducted in order to characterize the pathogenic potential of the B. cereus group. The aim of this study was to assess the sanitary potential risks of 174 B. cereus group strains i...
Article
Aims: To assess the bacterial diversity in the French egg processing industry and to explore the adhesion and spoilage potential of selected bacteria. Methods and results: Sterile stainless steel chips were suspended for two months inside the pipelines of seven egg processing companies, before and after the pasteurizer, at warm and cold seasons....
Article
Full-text available
Salmonella enterica serovar Enteritidis (SE) is the most frequently-detected Salmonella in foodborne outbreaks in the European Union. Among such outbreaks, egg and egg products were identified as the most common vehicles of infection. Possibly, the major antibacterial property of egg white is iron restriction, which results from the presence of the...
Article
Full-text available
Bacillus cereus group is widespread in nature and foods. Several members of this group are recognized as causing food spoilage and/or health issues. This study was designed to determine the prevalence and genetic diversity of the B. cereus group strains isolated in Tunisia from different foods (cereals, spices, cooked food, fresh-cut vegetables, ra...
Chapter
The microorganisms responsible for spoilage do not belong to a single taxonomic group. Bacteria, molds and yeasts can be the cause of alterations. The variety of food microorganisms depends on different factors. The first is relative to the nature of the food, for example, the fact that fish products may be contaminated by water, vegetables by soil...
Book
The microorganisms responsible for spoilage do not belong to a single taxonomic group. Bacteria, molds and yeasts can be the cause of alterations. The variety of food microorganisms depends on different factors. The first is relative to the nature of the food, for example, the fact that fish products may be contaminated by water, vegetables by soil...
Article
Increasing bacterial resistance towards antibiotics has stimulated research for novel antimicrobials. Proteins acting on bacterial membranes could be a solution. Lysozyme has been proven active against E. coli by disruption of both outer and cytoplasmic membranes, with dry-heating increasing lysozyme activity. Dry-heated lysozyme (DH-L) is a mixtur...
Article
Full-text available
Chicken egg white protects the embryo from bacterial invaders by presenting an assortment of antagonistic activities that combine together to both kill and inhibit growth.The key features of the egg white anti-bacterial system are iron restriction, high pH, antibacterial peptides and proteins, and viscosity. Salmonella enterica serovar Enteritidis...
Chapter
Salmonella Enteritidis currently represents the major risk of eggborne disease. The frequent association of this bacterium with egg infection is ascribed to various factors, including its spread and persistence in the breeding environment, its long-term ability to colonize the hen’s genital tract leading to horizontal transmission of the pathogen a...
Book
World egg consumption is increasing, particularly in developing countries. This creates new challenges, particularly for more intensive systems which have played a major role in increasing production and productivity. Intensive systems face a continuing threat from zoonoses. At the same time, consumer expectations about both safety, sensory and nut...
Article
On estime aujourd'hui à 25% les pertes d'aliments post-récolte et en aval, en raison de leur altération par des microorganismes. L'étude menée ici illustre le risque d'altération engendré par une rupture dans la chaîne du froid, en prenant comme modèle un aliment liquide pasteurisé et réfrigéré, riche en nutriments et dont la température ne doit pa...
Article
Full-text available
Le comité d’organisation : Véronique Broussolle, UMR 408 SQPOV, INRA PACA Avignon Frédéric Carlin, UMR 408 SQPOV, INRA PACA Avignon Didier Lereclus, UMR 319 Micalis, INRA Jouy-en-Josas Christina Nielsen-Leroux, UMR 1319 Micalis, INRA Jouy-en-Josas Vincent Sanchis, UMR 1319 Micalis, INRA Jouy-en-Josas
Article
With 215 eggs consumed per person in 2013, France remains one of the largest consumers of eggs in the European Union. Over a third of this consumption is in the form of egg products. Egg products from ‘first processing’ are defined as resulting from the breaking of table eggs, giving rise to the recovery of whole egg or separated egg yolk and eggwh...
Article
Lysozyme is mainly described active against Gram-positive bacteria, but is also efficient against some Gram-negative species. Especially, it was recently demonstrated that lysozyme disrupts Escherichia coli membranes. Moreover, dry-heating changes the physicochemical properties of the protein and increases the membrane activity of lysozyme. In orde...
Article
Antimicrobial resistance is currently an important public health issue. The need for innovative antimicrobials is therefore growing. The ideal antimicrobial compound should limit antimicrobial resistance. Antimicrobial peptides or proteins such as hen egg white lysozymes are promising molecules that act on bacterial membranes. Hen egg white lysozym...
Article
As a 1st step, this study aimed at investigating the microbial quality of liquid egg white in a French egg processing company. Thirty raw and 33 pasteurized liquid egg white samples were analyzed. Pasteurization was globally found efficient on mesophilic contaminants (1.7 ± 1.6 and 0.8 ± 0.9 log CFU/mL in raw and pasteurized samples, respectively),...
Book
Eggs have been used as key part of the human diet for millennia. They contain a great variety of nutrients and material to sustain life and growth. The role of the egg as natural source of vitamins, proteins, fats, and other nutrients, continues to develop. Some nutrients have a controversy in benefits and risks. This controversy is the subject of...
Book
This chapter focuses on microbial spoilage of shell eggs and egg products and reviews the spoilage characteristics, according to the type of product and the flora involved. The methods available for monitoring, reducing, and detecting the spoilage of egg and egg products also are reviewed.[br/] [br/] [br/] Under healthy breeding conditions, the egg...
Article
The reduction of wastes due to food spoilage may help save food resources among the current worldwide food production. Industrial egg products, obtained after egg breaking, recovery and pasteurisation of the internal egg components, are used in a wide range of food, including chilled egg- and milk-based food particularly susceptible to microbial sp...
Article
The consumption of chilled dairy desserts is increasing in the European Union. The famous French “île flottante”, consisting in a foam of egg white floating on a custard cream, represents a highly nutritive medium for bacterial growth and for the expression of enzymes susceptible to affect the food shelf-life at chilled temperatures. To avoid such...
Article
Full-text available
Although egg white is known as expressing efficient antimicrobial properties under physiological conditions, little is known on the microbial quality of industrial egg white. This issue is of great importance when egg white enters into the composition of highly perishable products, such as chilled egg-based desserts. Due to the high thermo-sensitiv...
Article
Antibiotic resistance causes public health problems and stimulates research for novelantimicrobials. Particular attention is given to molecules that limit drug resistancedevelopment.1Hen egg white lysozyme acting on the bacterial cell envelope through itsphysico-chemical properties is thus a good candidate.2,3However, its antimicrobial effectcaused...
Article
Full-text available
Bacillus cereus group bacteria are opportunistically pathogenic spore-forming microorganisms well known in the sector of pasteurized food products because of their involvement in spoilage events. In the sector of egg product processing, these bacteria may lead to important economic losses. It seemed then relevant to study their behavior in egg whit...
Article
Quatrième Edition du Congrès Maghrébin sur les Toxi-infections alimentaires "Sécurité sanitaire des aliments face aux mutations sociétales et à la mondialisation" Fès (Maroc) - 16-18 Avril 2014 Le Maroc accueille du 16 au 18 Avril 2014 à la ville de Fès, la quatrième édition du Congrès Maghrébin sur les Toxi-infections alimentaires sous le thème :...
Chapter
Milk and dairy products are important components of the diet worldwide. The quality and shelf life of liquid milk as well as dairy products are often compromised by flavor, odors, and visual defects arising from the bacterial growth and activities of heat-stable enzymes produced by psychrotrophic bacteria before processing. This article focuses on...
Article
To evaluate the food safety and spoilage risks associated with psychrotrophic Bacillus cereus group bacteria for the egg product industry, and to search for relevant risk markers. A collection of 68 psychrotrophic B. cereus group isolates, coming from pasteurized liquid whole egg products, was analyzed through a principal component analysis (PCA) r...
Article
For food as well as for medical applications, there is a growing interest for novel and natural antimicrobial molecules. Lysozyme is a promising candidate for the development of such molecules. This protein is largely studied and known for its muramidase activity against Gram-positive bacteria, but it also shows antimicrobial activity against Gram-...
Article
Liste des auteurs cf: EFSA Panel on Biological Hazards (BIOHAZ): biohaz@efsa.europa.eu European Food Safety Authority (EFSA)
Book
This article focuses on liquid milk spoilage (raw, pasteurized, and UHT), the characteristics of the spoilage, the species and the enzymatic activity involved, and the methods used to detect or predict milk spoilage.[br/] [br/] [br/] Milk and dairy products are important components of the diet worldwide. The quality and shelf life of liquid milk as...
Article
Antimicrobial drug resistance causes public health problems worldwide and stimulates research for novel antimicrobials.1 Particular attention is given to antimicrobial molecules that limit drug resistance development and have a large spectrum. Antimicrobial peptides and proteins are thus good candidates acting on the bacterial cell wall because of...
Article
Natural preservatives answer the consumer demand for long shelf-life foods, considering synthetic molecules are perceived as a health risk. Lysozyme is already used because of its muramidase activity against Gram-positive bacteria. It is also described active against some Gram-negative bacteria; membrane disruption would be involved, but the mechan...
Article
Full-text available
Bacterial membranes are often thought to be the main targets of the antimicrobial activity of egg white. In order to test this hypothesis, the state of the membranes of Escherichia coli K-12 cells during either bactericidal (45°C) or bacteriostatic (30°C) incubation in egg white at natural alkaline pH was studied by biochemical methods. Namely, the...
Article
Introduction: Bacterial spoilage involves visible modifications of texture, viscosity, colour, and/or flavour of liquid egg products. These later are widely used in various foodstuffs which microbiological quality is essential. Among the flora able to resist the mild heat treatments encountered by industrial egg products, the presence of the Bacill...
Article
Introduction: Egg products resulting from the breaking of shell eggs, giving rise to egg yolk and egg white, or whole egg, are used in highly diversified sectors for their functionalities (coloring, thickening, emulsifying and gelling properties), such as in dairy, meat and seafood products. Liquid egg products are generally pasteurized at moderate...
Article
Rennes – France) Quelques mois après l’autorisation de BACTOCELL® DRINK en eau de boisson, Lallemand Animal Nutrition a organisé sa deuxième journée technique BACTOCELL® pondeuses. Cet évènement a eu lieu le 26 Juin à Rennes où plus d’une trentaine de professionnels du monde avicole étaient présents. Le temps d’une demi-journée, différents sujets...
Article
Abstract 1. The growth of Bacillus cereus group bacteria often limits the shelf-life of pasteurised liquid egg products and is also a putative toxin producer. This study was performed to better understand the route of contamination by B. cereus in egg products by studying the factors affecting eggshell contamination on-farm. 2. Eggs were collected...
Article
Research in the domain of antimicrobial molecules is nowadays a hot topic because of the increasing bacterial resistance against antibiotics; moreover, consumers demand for natural food preservatives is growing. Proteins and peptides from different origins, such as hen egg white lysozyme, seem promising candidates for the discovery of novel and nat...
Article
Persistent bacteria in processing sites are of great concern in food industry, causing continuous recontamination and thus yielding compromised food quality and safety, lost productivity and environmental issues. The aim of this study was to develop a tool to reproduce bioadhesion under industrial conditions in order to investigate the impact of su...
Article
The adhesion of microorganisms to industrial surfaces is frequently observed in the food industry. Adhering bacteria can colonize the surfaces and organize into biofilms that provide cell protection against many stresses such as those due to disinfectants. Poorly controlled, they can be the source of food product contamination and/or food spoilage,...
Article
La formation de biofilm est un phénomène naturel et universel, i.e. l’adhésion microbienne aux surfaces est un phénomène progressif dans lequel les bactéries passent d’un mode planctonique à un mode sessile. Ce phénomène s’accompagne de modifications phénotypiques importantes comme l’expression de facteurs de virulence des cellules adhérées ou la s...
Article
Bacteria belonging to the Bacillus cereus group are commonly found in soil, air, dust, water and in many raw and processed foods. Several strains of this group have been implicated in food-borne illness. These bacteria are also prolific enzyme producers (lipases, proteases) and are recognised as causing spoilage in several pasteurised foodstuffs. S...
Article
This chapter reviews microorganisms responsible for egg contamination and their sources and gives a general description of current understanding of egg antimicrobial self-defence mechanisms. The methods limiting the presence and the development of microorganisms are discussed, both in the egg during development in the reproductive tract, and post-l...
Article
The aim of the present study was (i) to type, by genotypic and phenotypic methods, a collection of psychrotrophic bacteria belonging to the Bacillus cereus group collected in a farm and in 6 egg breaking industries during a period covering a warm and a cold season, and (ii) to characterize the egg product spoilage (growth in liquid whole egg) and t...
Article
Full-text available
The mechanism of egg white antimicrobial activity involves specific molecules and environmental factors. However, it is difficult to compare the data from the literature because of the use of various bacterial strains and incubation conditions. The aim of our study was to determine the effect of temperature, pH, inoculum size, and egg white protein...
Article
Full-text available
The presence of psychrotrophic or highly thermoresistant spore-forming bacteria in food and feedstuff responsible for food poisoning and spoilage raises major safety and economical issues. The aim of this study was to evaluate the performances of a ready-to-use PCR assay (alternative method) in comparison with the standard microbiological plating m...
Article
In Europe, the species Salmonella enterica, particularly the serovar S. Enteritidis, represents the major human pathogen related to egg consumption. Consequently, it is mainly used as a model in most studies interested in the antimicrobial activity of egg white. In order to explain this antimicrobial activity, the main hypotheses are, on the one ha...
Article
Comparison of two PCR methods targeting two different gene sequences for the detection of Bacillus cereus group bacteria in egg products
Article
Use of principal component analysis in order to link genotypic and phenotypic characters of psychrotrophic Bacillus cereus group isolates to their cytotoxic and spoilage potentials in egg-breaking industry
Article
Existe-t-il un lien entre les profils génotypiques et phénotypiques d'isolats psychrotrophes du groupe Bacillus cereus et leur potentiel cytotoxique et d'altération dans l'industrie des ovoproduits ?
Article
The risk of contamination by microorganisms, and mostly by Salmonella, is a major concern in the sectors of egg production and egg product manufacturing. Under healthy breeding conditions, the egg content is generally sterile. However, it can be contaminated by a diversified microbiota containing food spoilage microorganisms and sometimes pathogeni...
Article
Le risque de contamination par les microorganismes, et notamment par Salmonella, est une préoccupation majeure de la filière œufs et ovoproduits. Le contenu des œufs provenant d’élevages sains est en général stérile mais il peut toutefois être contaminé par une flore diversifiée contenant des microorganismes d’altération et parfois pathogènes. L’œ...
Article
A simplex polymerase chain reaction (PCR) has been applied for the specific detection of hen, duck, turkey, and guinea fowl in egg products using species-specific primers targeting the mitochondrial cytochrome b genes. The species-specific PCR yielded excellent results for identification of duck, turkey, and guinea fowl eggs in hen egg products, si...
Article
Identification of bacterial flora in spoiled liquid egg products and use of stainless steel chips to control biofilm development in an egg breaking factory
Article
Bacteria belonging to the Bacillus cereus group are found in soil, air, dust, water and in many raw and processed foods. Several strains of this group are able to produce toxins in food or in the human intestine that can lead to emesis or diarrhoea, respectively. Their various enzymatic activities are also recognised as causing food spoilage, even...
Article
Bacteria belonging to the Bacillus cereus group are Gram-positive, rod-shaped, and sporeforming micro-organisms widely distributed in nature. They are commonly found in soil, air, dust, water and in many raw and processed foods. Several strains of this group have been implicated in food-borne illness with two pathogenic forms generally benign and s...
Article
Full-text available
A psychrotolerant bacteria of the Bacillus cereus group was found responsible for the spoilage of whole liquid egg products. By sequencing a 16S rRNA region and performing a PCR amplification of specific 16S rRNA and cspA signatures, a Bacillus weihenstephanensis was identified. Characterization of this strain shows its ability to grow in defined m...
Article
The conventional plate-counting technique, while still routinely used in laboratories requiring micro-organism screening or enumeration, remains time-consuming and tiresome for the operator when large numbers of samples are assayed. We developed a miniaturized method based on serial tenfold dilution of samples in 96-well micro-plates followed by mu...
Article
Full-text available
Abstract The ability of flow cytometry to detect intracellular accumulation of poly(β-hydroxybutyrate) (PHB) in individual cells of Rhizobium meliloti was investigated using light scatter parameters. PHB accumulation during stationary phase was shown to form inclusion bodies inside cells which were detected by forward angle light scatter (FALS) par...
Article
Full-text available
In order to study the effects of saturated fatty acids on delta6-desaturase activity, rat hepatocytes in primary culture were incubated with lauric (C12:0), myristic (C14:0) or palmitic (C16:0) acids. After optimization, the standard in vitro conditions for the measurement of delta6-desaturase activity were as follows: 60 micromol x L(-1) alpha-lin...
Article
Full-text available
A single gene encoding a Delta6-desaturase (FADS2) has been isolated and characterized in mammalian species. This Delta6-desaturase plays a major role in the biosynthesis of PUFAs (polyunsaturated fatty acids). It catalyses the rate-limiting desaturation of linoleic acid (C(18:2) n-6) and alpha-linolenic acid (C(18:3) n-3) required for the biosynth...
Article
Full-text available
A single gene encoding a Delta6-desaturase (FADS2) has been isolated and characterized in mammalian species. This Delta6-clesaturase plays a major role in the biosynthesis of PUFAs (polyunsaturated fatty acids). it catalyses the rate-limiting desaturation of linoleic acid (C-18:2 n - 6) and alpha-linolenic acid (C-18:3 n - 3) required for the biosy...
Article
Full-text available
The Δ6-desaturase catalyzes key steps in long-chain polyunsaturated fatty acid biosynthesis. Although the gene coding for this enzyme has been isolated in diverse animal species, the protein structure remains poorly characterized. In this work, rat Δ6-desaturase expressed in COS-7 cells was shown to localize in the endoplasmic reticulum. As the enz...
Article
Full-text available
This study was designed to examine the metabolic fate of exogenous lauric acid in cultured rat hepatocytes, in terms of both lipid metabolism and acylation of proteins. Radiolabeled [14C]-lauric acid at 0.1 mM in the culture medium was rapidly taken up by the cells (94.8 +/- 2.2% of the initial radioactivity was cleared from the medium after a 4 h...
Article
Full-text available
A higher content of C16:1 n-10 has recently been reported in the preputial gland of mice with a targeted disruption of the gene encoding stearoyl-CoA desaturase 1 (SCD1−/− mice) when compared with wild-type mice. This result has provided the first physiological evidence for the presence and regulation of a palmitoyl-CoA Δ6-desaturase in mammals. To...
Article
Full-text available
In this study is presented the effect of fenofibrate, a prototypical peroxisome proliferator of the fibrate class, on wild-type and peroxisome proliferator-activated receptor alpha (PPARalpha)-/- mouse liver FA profile, desaturase mRNA levels, and activities. We established that, following peroxisome proliferator exposure, the hepatic FA profile wa...
Article
Full-text available
The recently cloned Delta6-desaturase is known to catalyse the first step in very-long-chain polyunsaturated fatty acid biosynthesis, i.e. the desaturation of linoleic and alpha-linolenic acids. The hypothesis that this enzyme could also catalyse the terminal desaturation step, i.e. the desaturation of 24-carbon highly unsaturated fatty acids, has...
Article
Full-text available
A screening of five lipases was carried out for the synthesis of wax esters from stoichiometric amounts of oleyl alcohol and milk fat in which long-chain fatty acid content (myristic acid, palmitic acid, stearic acid, and oleic acid) represents 70% of the total fatty acid fraction. The lipases from Alcaligenes sp. and Chromobacterium viscosum both...
Article
Eight microbial lipases and one animal tissue lipase were tested for their ability to support alcoholysis between triolein and stearyl alcohol to produce wax ester. The lipases from Alcaligenes sp. and Chromobacterium viscosum were shown to produce the best ester yield (about 53%); however, the reaction was catalyzed in a shorter length of time usi...
Article
Full-text available
1H NMR analysis was performed in order to identify the nature of the poly 3-hydroxyalkanoate (PHA) accumulated by Rhizobium meliloti M5N1 and determine its concentration within the cells. Since the PHA was identified as being poly 3-hydroxybutyrate (PHB), the method of quantification was previously tested on standard PHB. The use of either methanol...