Laurent Le Gendre

Bactericidal efficiency of UVA-active titanium dioxide thin layers on bacteria from food industry environments

Abstract Titanium dioxide (TiO2) thin layers have been deposited on glass substrates using radio frequency magnetron sputtering technique. The photocatalytic activity of the TiO2 thin layers has been investigated by a methylene blue discolouration test and reveals that films with an anatase structure present the highest performance. Bactericidal activity of the anatase-phase TiO2 layer against food-borne bacteria has then been tested by enumeration of the adherent cells, after adhesion and a subsequent UVA illumination. A decrease of the adherent bacteria number equal to −1.2, −2.6 and −2.3 log is reached for Y. enterocolitica, L. monocytogenes and P. fragi, respectively. SEM observations exhibit bacterial cells with damaged walls for all bacteria. Applied on materials present in the food plants, these TiO2 thin layers may be an effective way for the hygienic conception of the equipment to reduce the biofilm formation and thus, to ensure food safety.

Synthesis and Structural Characterization of Glass Foam Composites for Electromagnetic Application

This article deals with the synthesis and structural characterization of glass foams made from cullet and loaded with carbon fibers or used tires for electromagnetic absorption application. All the raw materials used for this work come from recycling or reconditioning. Two carbonaceous loads are tested; the carbon fiber scraps are used because they show an interest in the field of absorption and parallel to this, another load type (tire waste) is used for its high carbon content. This novel later load is used, to our knowledge, for a first time. Samples with different weight contents of the loads are achieved and characterized. The used percentages of loads, are respectively, between 0 and 10 wt.% and between 0 and 20 wt.% for carbon fibers and tire waste. In this article, we present and discuss the elaboration method, the morphological and structural results of the loaded glass foam composites. A low density was obtained from both composite, with a density between 0.28 and 0.53 g/cm3. An excess content of tire waste load leads to “collapse” of the gas bubbles during the heat treatment of the sample which induces an increase in the density of the composite. This is due to the decomposition of this load during the elaboration process. This result is confirmed by the scanning electron microscopy observation and also by gravimetric thermal analysis of the tire waste. Contrary to this, composites loaded with carbon fibers show better structure homogeneity and non-decomposition of carbon fibers during a heat treatment.

Antimicrobial activity of stainless steel with a modified TiN upperlayer on meat related contaminants

Advanced material with antibacterial properties would be a promising way to improve the disinfection process in food plants. Our objective was to combine the bactericidal effect of TiO2 with the mechanical strength of TiN coatings. A TiO2 rutile film was obtained after annealing of a supplied 316 stainless steel with a TiN coating. This TiO2 upperlayer displays a photocatalytic activity under UV light exposure. The substrates with the TiN coating and the TiO2 upperlayer are more hydrophobic than the 316 control. The adhesion of either Listeria or Pseudomonas, on 316-TiN is characterized by the presence of clusters of cells, while the oxidation of the TiN surface leads to a more hydrophilic layer where cells are individualized. After UV illumination of the adherent cells and subsequent growth, the residual bacterial population present on 316-TiO2 is lower than that present on the 316-TiN. The bactericidal effect is more important on Listeria than on Pseudomonas.