Impact of the surface properties of lactic bacteria on the stability of emulsions

Bacteria have physicochemical surface properties which depend on the chemical composition of the cell surface. These characters proceed from several type of physicochemical interactions and are involved in attachment processes of microorganisms to surfaces. Thus they are of interest in several areas, as biomedicine, formation of biofilms and adhesion to apolar surfaces. Moreover, food matrix are complex heterogeneous media, which structure settles on interaction forces between molecules (van der Waals, electrostatic or structural forces…). When bacteria are present in a matrix, it is probable that their surface interacts with the other constituents. So far, few studies have mentioned this subject. In order to understand the involvement of cells surface properties in a food matrix, the effect of surface properties of lactic bacteria on the stability of model emulsions were studied. The results showed that the choice of a bacterium according to its surface properties may have a strong impact on the stability and on the behavior of an emulsion

Achieving Reactive Species Specificity within Plasma Activated Water through Selective Generation using Air Spark and Glow Discharges

Plasma activated liquids (PAL) attract increasing interest with demonstrated biological effects. Plasma exposure in air produces stable aqueous reactive species which can serve as chemical diagnostics of PAL systems. Here, we tailor aqueous reactive species inside plasma activated water (PAW) through treating water with AC air spark and glow discharges in contact with water. Chemical probing demonstrated species specificity between two types of PAW. Spark discharge PAW contains 2 2 H O and 3 NO , while 2 NO and 3 NO are generated in glow discharge PAW. Species formation in different PAWs have been discussed in terms of discharge mechanisms and liquid phase chemistry process. Species specificity can provide richer parametric spaces for producing PALs with controlled impact and dosage achievable by combining discharge modes or mixing different PALs

BioRock:new experiments and hardware to investigate microbe–mineral interactions in space

In this paper, we describe the development of an International Space Station experiment, BioRock. The purpose of this experiment is to investigate biofilm formation and microbe–mineral interactions in space. The latter research has application in areas as diverse as regolith amelioration and extraterrestrial mining. We describe the design of a prototype biomining reactor for use in space experimentation and investigations on in situ Resource Use and we describe the results of pre-flight tests

Translation of plasma technology from the lab to the food industry

The potential of cold plasma as a food processing aid has been demonstrated for a range of processes and products. The potential applications of plasma technology are extensive and include: microbial decontamination, pest control, toxin elimination, food and package functionalisation and many others. However, studies reported to date have principally been at laboratory scale. This paper discusses the status and challenges of transferring the technology to the industry. The major challenges discussed for adoption of atmospheric plasma as a food processing tool by industry are: 1) demonstration of product/process specific efficacies; 2) development of process compatible technology designs and scale-up; 3) effective process control and validation; 4) regulatory approval and 5) consumer acceptance

Characterising the impact of post-treatment storage on chemistry and antimicrobial properties of plasma treated water derived from microwave and DBD sources

The biological effects of atmospheric cold plasma generated reactive species are mediated through and at a liquid interface. The diversity of antimicrobial efficacy or intensity of effects may differ with respect to the plasma device or set up, and it is important to understand how these differences occur to advance understanding and successful applications. Thus, plasma treated water (PTW) from a microwave driven plasma source (PTW-MW) and plasma treated water from a di-electric barrier discharge system (PTW-DBD) were compared in terms of long lived reactive species chemical composition and antimicrobial activity. The influence of a post-treatment storage time (PTST), where reactive species in the gas phase were maintained in contact with the liquid was investigated. Nitrogen-based chemistry dominated in PTW-MW, with high concentrations of nitrous acid decomposing to nitrite and nitrate, while H2O2 and nitrate were predominant in PTW-DBD. PTST could enhance H2O2 concentrations in di-electric barrier PTW over time while nitrous acid, the main oxidative species in microwave driven PTW, decreased. This work highlights that plasma treated water presents a resource comprising a range of different compounds, stabilities and reactivities which may be tunable to specific applications

Atmospheric air plasma induces increased cell aggregation during the formation of Escherichia coli biofilms

Atmospheric air plasma has previously been shown to be a novel and effective method for biofilm eradication. Here we study the effects of plasma on both microbial inactivation and induced structural modification for forming biofilms. New structures are created from aggregates of extracellular polysaccharides and dead bacterial cells, forming a protective and resilient matrix in which the remaining living cells grow and reproduce under proper growth conditions. The new colonies are found to be more resilient in this state, reducing the efficacy of subsequent plasma treatment. We verify that the observed effect is not caused by chemicals produced by plasma reactive species, but instead by the physical processes of drying and convection caused by the plasma discharge

Vers de nouvelles voies de décontamination des surfaces ?

L’éradication des micro-organismes implantés sur des surfaces, qu’elles soient biologiques ou inertes, est un point clé de la maîtrise de la sécurité sanitaire dans de nombreux secteurs, notamment le domaine médico-hospitalier, les industries agroalimentaires ou pharmaceutiques, les environnements domestiques et les collectivités. Des techniques de décontamination sont actuellement disponibles, dont certaines sont très utilisées comme la désinfection par des agents chimiques de synthèse. Mais ces techniques ont parfois une effi cacité limitée ou des inconvénients non négligeables tels que des risques pour la santé des opérateurs ou de pollution environnementale.Les désinfectants sont des agents chimiques utilisés pour inactiver les micro-organismes pathogènes ou d’altération. Même si, la plupart du temps, ces désinfectants inactivent effi cacement les contaminants microbiens, il arrive que certaines bactéries pathogènes survivent et persistent dans les environnements, posant alors de graves problèmes de santé publique. Cette capacité de survie est souvent associée à la présence de biofi lms sur les surfaces (Vestby et al., 2009). Ces structures tridimensionnelles sont constituées de micro-organismes associés à une surface, souvent englués dans une matrice exopolymérique, et montrent généralement une plus grande résistance à l’activité bactéricide des désinfectants que les mêmes souches à l’état libre. La résistance des biofilms aux agents de désinfection est un phénomène complexe, multifactoriel, et non intégralement élucidé aujourd’hui (Bridier et al., 2011

Teaching microbiological food safety through case studies

Higher education students usually ask for more training based on case studies. This was addressed by designing a specific food safety module (24 hours) in which students were shown how to predict microbiological risks in food products i.e. they were asked to determine product shelf-life according to product formulation, preservation methods and consumption habits using predictive microbiology tools. Working groups of four students first identified the main microbiological hazards associated with a specific product. To perform this task, they were given several documents including guides for good hygiene practices, reviews on microbiological hazards in the food sector, flow sheets, etc…  After three-hours of work, the working groups prepared and gave an oral presentation in front of their classmates and professors. This raised comments and discussion that allowed students to adjust their conclusions before beginning the next step of their work. This second step consisted in the evaluation of the safety risk associated with the two major microbiological hazards of the product studied, using predictive microbiology. Students then attended a general lecture on the different tools of predictive microbiology and tutorials (6 hours) that made them familiar with the modelling of bacterial growth or inactivation. They applied these tools (9 hours) to predict the shelf-life of the studied product according to various scenarios of preservation (refrigeration, water activity, concentration of salt or acid, modified atmosphere, etc…) and/or consumption procedures (cooking). The module was concluded by oral presentations of each working group and included student evaluation (3 hours).</p

Risques microbiologiques alimentaires

Pour garantir et maîtriser la sécurité microbiologique des aliments et prévenir les crises sanitaires alimentaires, la connaissance et la surveillance des microorganismes pathogènes depuis la production primaire jusqu’à la distribution des denrées alimentaires en passant par la transformation, sont indispensables.Cet ouvrage de référence traite des dangers microbiologiques alimentaires majeurs (microorganismes infectieux ou toxines d’origine microbienne) et des risques associés pour l’Homme. Illustré de nombreux schémas et tableaux de synthèse, ce livre fait un point complet sur les notions fondamentales de microbiologie générale, de physiologie microbienne et de modélisation, en les appliquant aux microorganismes pathogènes des aliments et en y intégrant les dernières avancées. Il présente ensuite les outils de gestion du risque microbiologique mis en place au niveau européen et français. Enfin, les microorganismes avérés ou émergents d’intérêt font l’objet de monographies claires et détaillées permettant de bien les connaître pour mieux les maîtriser.Cet ouvrage s’adresse aux managers, ingénieurs et techniciens des industries agroalimentaires (des secteurs qualité-hygiène, production, achats, recherche et développement...), aux professionnels du contrôle sanitaire et de la gestion du risque (laboratoires d’analyses et instances officielles) ainsi qu’aux enseignants-chercheurs et aux étudiants dans le domaine de la microbiologie appliquée à l’agroalimentaire et des risques sanitaires