Les biosurfactants, des biomolécules à forte potentialité d'application

Biosurfactants are surface-active molecules synthesized by certain microorganisms. Their chemical nature as well as their surface-active properties are dramatically dependent on the type of microorganism (bacteria, yeasts, moulds), on the individual strain tested and on the available nutrients. The various known biosurfactants comprise glycolipids, lipopeptides, phospholipids, neutral lipids, fatty acids or lipopolysaccharides. As their chemical synthetic counterparts, they may exhibit emulsifying, foaming, wetting or dispersing properties, as well as more specific characteristics i.e. antibiotic activity. Such properties may be still efficient in extreme conditions such as acidic pH and high temperatures. In regard to their potentiality and their low toxicity, they are nowadays used in different applications such as environmental protection, petroleum industry, agronomy or cosmetology and should shortly settle in new sectors such as food processing, pharmaceutical industries or health care. The main objective of the following review is to synthesize the present knowledge in this research area.Les biosurfactants sont des molécules tensioactives produites par certains micro-organismes. Leur nature tout comme leur pouvoir tensioactif sont fortement dépendants du type de micro-organisme utilisé (bactéries, levures, champignons), de la souche testée ainsi que du substrat nutritif disponible pour le développement cellulaire. Parmi les différents biosurfactants recensés, on trouve aujourd’hui des glycolipides, des lipopeptides, des phospholipides, des lipides neutres, des acides gras ou des lipopolysaccharides. Tout comme leurs homologues de synthèse chimique, ils peuvent avoir des propriétés émulsifiantes, moussantes, mouillantes ou encore dispersantes, mais également des propriétés plus spécifiques (i.e. propriétés antibiotiques). Certaines de ces propriétés peuvent, de plus, être conservées dans des conditions extrêmes utilisation telles que pH acides, températures élevées, etc. Compte tenu de leurs potentialités et de leur innocuité, ils sont aujourd’hui utilisés dans différents domaines d’application tels que l’environnement, l’industrie pétrolière, l’agronomie ou encore la cosmétologie et devraient rapidement trouver leur place dans de nouveaux secteurs d’applications tels que les industries agroalimentaires, pharmaceutiques ou encore le domaine médical. La revue présentée ici a pour principal objectif de synthétiser les connaissances acquises à ce jour dans ce domaine

Material influence on biocontamination level and adhering cell physiology

In most environments, association with a surface in a structure known as a biofilm is the prevailing microbial lifestyle. Several factors may influence the biofilm formation e.g. nutrients, temperature, flow velocity, initial microflora and the nature of materials. Considering the biocontamination mechanism described in four steps, the initial adhesion is a key element in the biocontamination phenomenon and the substratum is of major concern in controlling bacterial adhesion. Stainless steel is well used in numerous markets because of its high cleanability and corrosion resistance properties. However, other materials are put forward by focusing on properties which differentiate them from those of stainless steel. Thereby, to select the material best suited to the problem, there should have data on their aptitude for biocontamination as well as adhesion impact on cell physiology. For all materials, the ratio of dead adhering cells is lower than 55%. The results obtained show that cell injury is not higher on material known to be bactericidal than on other ones.Dans la plupart des environnements, les microorganismes vivent pr ́ ef ́ erentiellement au sein de biofilms. De nombreux facteurs influencent leur formation i.e. les nutriments, la temp ́ erature, le r ́ egime du fluide environnent, la microflore et les mat ́ eriaux. Dans le m ́ ecanisme de biocontamination, d ́ ecrit en quatre ́ etapes successives, l’adh ́ esion initiale est un ́ el ́ ement cl ́ e de la bioadh ́ esion et les mat ́ eriaux un ́ el ́ ement majeur pour son contr ˆ ole. L’acier inoxydable est tr ` es utilis ́ e dans de nombreux secteurs d’activit ́ e pour sa bonne nettoyabilit ́ e et son excellente r ́ esistance ` a la corrosion. Pour se diff ́ erencier, certains mat ́ eriaux mettent en avant d’autres propri ́ et ́ es.Ainsi,las ́ election du mat ́ eriau le mieux adapt ́ e ` a un probl ` eme donn ́ en ́ ecessite de connaitre son aptitude ` a la biocontamination ainsi que son impact sur la physiologie des microorganismes. Pour tous les mat ́ eriaux test ́ es, la mortalit ́ e des bact ́ eries adh ́ erentes est inf ́ erieure ` a55%.Lesr ́ esultats obtenus ont montr ́ e qu’un mat ́ eriau dit antimicrobien n’induit pas plus de cellules endommag ́ ees comparativement aux autres mat ́ eriaux

Hygiène. Guide pratique pour la réalisation d'essais d'adhésion microbienne.

Dans les industries agro-alimentaires, la biocontamination des surfaces peut entraîner des pertes de rentabilité importantes liées à l’encrassement des matériaux (augmentation de la consommation d’énergie, réduction de la productivité, dégradation du produit fini…). Lorsqu’elle implique des germes pathogènes, cette biocontamination peut être à l’origine de problèmes de santé publique parfois sévères. Conscient des enjeux socio-économiques et scientifiques que peuvent générer de tels phénomènes bioadhésifs, le RMT ACTIA CHLEAN s’est fixé plusieurs missions, parmi lesquelles l’amélioration des connaissances des phénomènes bioadhésifs pour proposer, aux industriels et aux filières du secteur agro-alimentaire, des solutions innovantes dans la maîtrise du risque sanitaire des produits et de l’hygiène des matériaux. Dans ce contexte, il est apparu nécessaire de proposer des méthodes harmonisées pour étudier l’adhésion microbienne, première étape de la formation de biofilms, au travers de ce guide. Ces méthodes et les recommandations qui y sont associées sont destinées à tout laboratoire qui souhaite mener des travaux nécessitant des surfaces contaminées (cellules adhérentes ou biofilm) pour, par exemple : - évaluer l’efficacité d’agents nettoyants et désinfectants; - étudier les biotransferts de la surface vers l’aliment; - déterminer l’aptitude à l’adhésion de différents micro-organismes; - optimiser des techniques de décrochement;

Surface Engineering and Cell Adhesion

Cell adhesion is a multi-process phenomenon involving physical, physico-chemical and biological mechanisms. The complexity of interfaces is the reason why progress in the theory of cell adhesion has been slow. Greater understanding of interaction mechanisms has been enhanced by complete knowledge of supports and of biological components, in particular the extracellular matrix, membrane walls, cell multiplication processes and apoptosis. The construction of novel surfaces with strongly hydrophilic or ultrahydrophobic properties has allowed new theoretical advances, while at the same time offering numerous and varied technological applications. These include: • Bioadhesion with mechanical anchoring using ubiquitous surface roughness and deformability of certain micro-organisms. • Physico-chemical bioadhesion or repellence resulting mainly from the energy characteristics of support surfaces. • Processes of sorting and guidance by biomolecules present at the support–biofilm interface, generating biochemical responses that can induce cell multiplication or degeneration (as in cancer), or cell death

Non-invasive SFG spectroscopy: a tool to reveal the conformational change of grafted chains due to bacterial adhesion

Nirmala Ramanujam; Jürgen Popp, Editor(s)In many fields such as biomedical or food industry, surface colonization by micro-organisms leads to biofilms formation that are tridimentional biostructures highly resistant to the action of antimicrobials, by mechanisms still unclear. In order to deepen our understanding of the initial interaction of bacteria cells with a solid surface, we analyze by in situ vibrational Sum Frequency Generation (SFG) spectroscopy the effect of the adhesion of hydrophilic Lactoccocus lactis bacteria and its hydrophobic mutants in distilled water on a self-assembled monolayer (SAM) of octadecanethiol (ODT) on a gold film. When a homogeneous bacterial monolayer is deposited on this ordered surface, SFG spectrum of the ODT SAM shows significant intensity changes from that in air or in water. Its modelling as a function of conformation allows to distinguish optical effects due to the water solution surrounding bacteria from conformational changes of the ODT SAM due to the presence of the bacteria cells. Futhermore, bacterial adhesion induces different measurable effects on the ODT SAM conformation, depending on the hydrophobic / hydrophilic character of the bacterial surface. Such a result deserves to be taken into account for the design of new materials with improved properties or to control biofilm formation

Decontamination of chemical and microbial targets using gliding electrical discharge

Chapter VIDecontamination of chemical and microbial targets using gliding electrical discharg

Increase in the hydrophilicity and Lewis acid-base properties of solid surfaces achieved by electric gliding discharge in humid air: effects on bacterial adherence

This study addressed the effects of treatment with gliding discharge plasma on the surface properties of solid materials, as well as the consequences concerning adherence of a model bacterium. As evaluated by contact angles with selected liquids, plasma treatment caused an increase in surface hydrophilicity and in the Lewis acid-base components of the surface energy of all materials tested. These modifications were more marked for low density polyethylene and stainless steel than for polytetrafluoroethylene. After treatment, the hydrophilicity of the materials remained relatively stable for at least 20 days. Moreover, analysis of the topography of the materials by atomic force microscopy revealed that the roughness of both polymers was reduced by glidarc plasma treatment. As a result of all these modifications, solid substrates were activated towards micro-organisms and the adherence of S. epidermidis, a negatively charged Lewis-base and mildly hydrophilic strain selected as the model, was increased in almost all the cases tested

Impact on disinfection efficiency of cell load and of planktonic/adherent/detached state: case of Hafnia alvei inactivation by Plasma Activated Water

This paper describes the effects of initial microbial concentration and planktonic/adherent/detached states on the efficiency of plasma-activated water. This disinfecting solution was obtained by treating distilled water with an atmospheric pressure plasma produced by gliding electric discharges in humid air. The inactivation kinetics of planktonic cells of Hafnia alvei (selected as a bacterial model) were found to be of the first order. They were influenced by the initial microbial concentration. Efficiency decreased when the initial viable population N0 increased, and the inactivation rate kmax was linearly modified as a function of Log10 (N0). This relation was used to compare planktonic, adherent, and detached cells independently from the level of population. Bacteria adhering to stainless steel and high-density polyethylene were also sensitive to treatment, but at a lower rate than their free-living counterparts. Moreover, cells detached from these solid substrates exhibited an inactivation rate lower than that of planktonic cells but similar to adherent bacteria. This strongly suggests the induction of a physiological modification to bacteria during the adhesion step, rendering adherent—and further detached—bacteria less susceptible to the treatment, when compared to planktonic bacteria

Radical polymerization and preliminary microbiological investigation of new polymer derived from myrtenol

A new methacrylic monomer derived from myrtenol, an essential oil possessing biocidal properties extracted from Myrtus communis L., was prepared in one step and named myrtenyl methacrylate. Conventional radical polymerization was performed in solution with 2,2'-azobis(2-methylpropionitrile) as thermal initiator in the temperature range 60-80 degrees C. Influences of reaction time, temperature and initiator concentration on monomer conversion and molar masses were studied. Controlled radical polymerization experiments were performed using the Atom Transfer Radical Polymerization techniques, leading to the formation of polymers with controlled molar masses and narrow molar mass distribution. Microbiological tests of these (macro)molecules were carried out using planktonic and adhesion tests with gram-positive and gram-negative bacteria in order to evaluate their antibacterial properties. (C) 2011 Elsevier Ltd. All rights reserved

Microbial inactivation using plasma-activated water obtained by gliding electric discharges

Aim: To evaluate the microbial disinfection efficacy of a plasmachemical solu-tion obtained by the activation of water with gliding electric discharges.Methods and Results: Distilled water was activated for 5 min by a nonthermalquenched plasma of the glidarc type operating in humid air and at atmosphericpressure. The plasma-activated water (PAW) was then used to treat planktonicand adherent cells of Staphylococcus epidermidis, Leuconostoc mesenteroides (asmodels of Gram-positive bacteria), Hafnia alvei (a Gram-negative bacteria) andSaccharomyces cerevisiae (as a yeast model). The treatments were less efficienton adherent cells than on planktonic cells in the case of bacteria, but not ofS. cerevisiae. Inactivation was more effective for bacteria than for the yeast.Conclusions: Significant reductions in microbial populations were achieved inall cases, demonstrating the effectiveness of this new approach to treat conta-minated media.Significance and Impact of the Study: PAW is a promising solution withpotential application to the decontamination of equipment and surfaces