Alteration of the phospho- or neutral lipid content and fatty acid composition in Listeria monocytogenes due to acid adaptation mechanisms for hydrochloric, acetic and lactic acids at pH 5.5 or benzoic acid at neutral pH

This study provides a first approach to observe the effects on Listeria monocytogenes of cellular exposure to acid stress at low or neutral pH, notably how phospho- or neutral lipids are involved in this mechanism, besides the fatty acid profile alteration. A thorough investigation of the composition of polar and neutral lipids from L. monocytogenes grown at pH 5.5 in presence of hydrochloric, acetic and lactic acids, or at neutral pH 7.3 in presence of benzoic acid, is described relative to cells grown in acid-free medium. The results showed that only low pH values enhance the antimicrobial activity of an acid. We suggest that, irrespective of pH, the acid adaptation response will lead to a similar alteration in fatty acid composition [decreasing the ratio of branched chain/saturated straight fatty acids of total lipids], mainly originating from the neutral lipid class of adapted cultures. Acid adaptation in L. monocytogenes was correlated with a decrease in total lipid phosphorus and, with the exception of cells adapted to benzoic acid, this change in the amount of phosphorus reflected a higher content of the neutral lipid class. Upon acetic or benzoic acid stress the lipid phosphorus proportion was analysed in the main phospholipids present: cardiolipin, phosphatidylglycerol, phosphoaminolipid and phosphatidylinositol. Interestingly only benzoic acid had a dramatic effect on the relative quantities of these four phospholipids

Effet de la direction d'injection lors de l'élaboration de polypropylène renforcé avec de la farine de bois d'olivier: propriétés ultrasonores et morphologiques

Proceedings of the Second International Conference on Acoustics and Vibration (ICAV2018), March 19-21, 2018, Hammamet, TunisiaInternational audienceAlthough the anisotropy of wood fibers is reasonably well established, the anisotropy of injection molded wood fiber composites is not well understood. For this, fiber distribution is an important parameter in determining the properties of the composite. This work investigates the application of ultrasonic testing in evaluating natural fiber thermoplastic composites reinforced with olive wood flour (OWF). The characterization of sound propagation speed in the composite is intended to be a tool for evaluating the bio-composite namely fiber distribution and the effects of the direction of injection during the elaboration of the composite. The quality of fiber distribution homogeneity can be assessed by mapping the returning signals of the emitted longitudinal ultrasonic wave. This study presents the measured sound speeds for a composite system of OWF and polypropylene (PP) using immersion measurements. It is known that the longitudinal wave velocity is a function of the material property, which in turn is a function of fiber content and adhesion efficiency. Therefore, the aim of this work is to study the feasibility of using the ultrasonic longitudinal sound wave and the time of flight TOF instead of the morphological analysis with the scanning electron microscope, which is much more expensive and complicate

Antilisterial Activity on Poultry Meat of Amylolysin, a Bacteriocin from Bacillus amyloliquefaciens GA1

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