Antibiofilm Activity of an Exopolysaccharide from Marine Bacterium Vibrio sp. QY101

Bacterial exopolysaccharides have always been suggested to play crucial roles in the bacterial initial adhesion and the development of complex architecture in the later stages of bacterial biofilm formation. However, Escherichia coli group II capsular polysaccharide was characterized to exert broad-spectrum biofilm inhibition activity. In this study, we firstly reported that a bacterial exopolysaccharide (A101) not only inhibits biofilm formation of many bacteria but also disrupts established biofilm of some strains. A101 with an average molecular weight of up to 546 KDa, was isolated and purified from the culture supernatant of the marine bacterium Vibrio sp. QY101 by ethanol precipitation, iron-exchange chromatography and gel filtration chromatography. High performance liquid chromatography traces of the hydrolyzed polysaccharides showed that A101 is primarily consisted of galacturonic acid, glucuronic acid, rhamnose and glucosamine. A101 was demonstrated to inhibit biofilm formation by a wide range of Gram-negative and Gram-positive bacteria without antibacterial activity. Furthermore, A101 displayed a significant disruption on the established biofilm produced by Pseudomonas aeruginosa, but not by Staphylococcus aureus. Importantly, A101 increased the aminoglycosides antibiotics' capability of killing P. aeruginosa biofilm. Cell primary attachment to surfaces and intercellular aggregates assays suggested that A101 inhibited cell aggregates of both P. aeruginosa and S. aureus, while the cell-surface interactions inhibition only occurred in S. aureus, and the pre-formed cell aggregates dispersion induced by A101 only occurred in P. aeruginosa. Taken together, these data identify the antibiofilm activity of A101, which may make it potential in the design of new therapeutic strategies for bacterial biofilm-associated infections and limiting biofilm formation on medical indwelling devices. The found of A101 antibiofilm activity may also promote a new recognition about the functions of bacterial exopolysaccharides

Voies de recherche en matière de récupération assistée du pétrole par tensio-actifs Research Lines in Enhanced Oil Recovery by Surfactants

Quelle que soit la conjoncture économique, le procédé de récupération assistée du pétrole par injection d'agents tensio-actifs nécessite une mise en oeuvre très élaborée pour tirer le meilleur parti des produits et donc pour franchir le seuil de rentabilité. Il apparaît par ailleurs que son champ d'application doit être étendu aux conditions de réservoir couramment rencontrées, notamment les fortes salinités, par l'utilisation de structures chimiques adaptées. Pour réduire les pertes de tensio-actifs par adsorption sur la roche, et par suite, préserver l'efficacité du fluide micellaire, deux techniques sont étudiées à l'Institut Français du Pétrole. L'une d'entre elles consiste à réduire l'adsorption en augmentant le pH de la formation à l'aide d'agents alcalins. Dans l'autre méthode, les molécules adsorbées sont remises en solution par un agent désorbant ajouté à l'eau de chasse. L'extension du procédé aux gisements salés est illustrée avec une famille de tensio-actifs qui ont un comportement prometteur dans ces conditions, les sulfonates d'oléfines alpha. Il apparaît que l'efficacité interfaciale de ces produits ne doit pas être seule prise en compte, mais également la solubilité, la stabilité chimique, le comportement rhéologique et l'adsorption sur les surfaces minérales. <br> No matter what the economic situation may be, the process of enhanced oil recovery (EOR) by surfactant flooding requires very sophisticated implementation to take maximum advantage of the chemicals and hence to cross the threshold of economic feasibility. It seems, moreover, that the scope of application of this process must be enlarged to meet the reservoir conditions commonly encountered, particularly high salinity, by the use of suitable chemical structures. To reduce surfactant losses by adsorption on the rock and then to preserve the efficiency of the micellar fluid, two techniques are being investigated at the Institut Français du Pétrole. One of them consists in reducing adsorption by increasing the pH of the formation by means of alkaline agents. In the other method, adsorbed molecules are brought back to solution by a desorbing agent added to the chase water. Extension of the process to salty formations is illustrated with a surfactant family having a promising behavior under such conditions, i. e. alpha-olefin sulfonates. The interfacial efficiency of these products does not seem to be the only positive factor, but also their solubility, chemical stability and rheological behavior as well as their adsorption mineral surfaces

Retention des additifs tensio-actifs par les surfaces solides

SIGLECNRS-CDST / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc