Efecto del empleo de árido siderúrgico en las propiedades de las mezclas bituminosas

En el conjunto de los estudios realizados en el departamento ITT de nuestra escuela, con el objetivo de trabajar tanto en la formulación de mezclas asfálticas y nuevas tecnologías de pavimentación que proporcionen elevadas prestaciones de seguridad y sostenibilidad de las carreteras en general. Esta tesina pretende llegar a conocer si las escorias siderúrgicas son aptas o no, en base al alto coeficiente de pulimento acelerado (CPA) que tiene este nuevo árido, para formar parte de las mezclas bituminosas en las capas superficiales de la carretera. Los estudios realizados pretender observar la respuesta que tiene esta nueva mezcla bituminosa en aspectos como la estabilidad, deformaciones, resistencia, tracción indirecta, rigidez, etc

Production of bacterial oxylipins by Pseudomonas aeruginosa 42A2

Podeu consultar el llibre complet a: http://hdl.handle.net/2445/67430Oxylipins are a family of natural compounds that are reported to perform a variety of biological functions. Besides the biological properties of such compounds, interest in hydroxy fatty acids is increasing, due to the industrial applications of these renewable compounds as a starting material for resins, emulsifiers, plastics or polyesters. Hydroxy fatty acids are used as thickeners in a new generation of emulsifiers and lubricants, to reach new levels of performance. When grown in submerged culture with oleic or linoleic acid, Pseudomonas aeruginosa 42A2 produced several oxylipins. In this study, oxylipin production and its applications are examined

Optimizing the production of the biosurfactant lichenysin and its application in biofilm control

Aims: Apply response surface methodology (RSM) to develop and optimize an economical medium for lichenysin production, which is a surfactant produced by Bacillus licheniformis and evaluate the application of lichenysin in the prevention and disruption of pathogenic micro-organism biofilm that creates health problems in the food industry and hospitals. Results: An economical medium containing molasses was optimized to enhance lichenysin production by RSM. A production of 3.2 g l 1 of lichenysin was achieved with an optimum medium containing 107.82 g l 1 of molasses, 6.47 g l 1 of NaNO3 and 9.7 g l 1 of K2HPO4/KH2PO4, in which molasses and phosphate salts had a significant effect on biosurfactant production. Lichenysin was effectively applied in a surface pre-treatment to avoid microbial biofilm development of methicillin-resistant Staphylococcus aureus (MRSA) (68.73%) and Candida albicans (74.35%), with ED50 values of 8.3 and 17.2 lg ml 1 respectively. It was also very efficient in a surface posttreatment to remove biofilms of MRSA (55.74%) and Yersinia enterocolitica (51.51%), with an ED50 of 2.79 and 4.09 lg ml 1 respectively. Conclusions: Lichenysin was found to have notable anti-adhesion activity, being able to prevent and eliminate the biofilm formation by pathogenic strains associated with foodborne illness. This new medium resulted in a fourfold increase in production compared with the nonoptimized medium. Significance and Impact of the Study: Molasses can be regarded as a useful resource for biotechnological applications, such as the production of lichenysin. The use of agro-industrial substrates has an important role in the sustainable and competitive development of several industrial sectors, as well as in industrial residues management. Additionally, lichenysin is particularly effective in preventing biofilm formation by strains problematic for the food industry and in the hospital environment. Lichenysin also efficiently disrupts biofilm

Micellization and antimicrobial properties of surface active ionic liquids containing cleavable carbonate linkages

Imidazolium-based ionic liquids (ILs) containing cleavable carbonate linkages, 1-alkyloxycarbonyloxyethyl-3-methylimidazolium chlorides with alkyl chains of 10, 12, and 14 carbon atoms, were synthesized, and their self-assembly behavior and antimicrobial activity were investigated. Differential scanning calorimetry and polarized optical microscopy studies reveal that carbonate-functionalized ILs form stable thermotropic smectic liquid-crystalline phases over a wide range of temperature. The surface activity and aggregation behavior of these new ILs were investigated by tensiometry, conductometry, potentiometry, and spectrofluorimetry. The size of aggregates was examined by dynamic light scattering (DLS). Carbonate-functionalized ILs display a higher adsorption efficiency and a lower critical micelle concentration (cmc) than simple alkyl-chain-substituted ILs. The insertion of a carbonate ester moiety in the alkyl side chain favors adsorption at the air-water interface and micellization in the bulk solution when compared to nonfunctionalized ILs. DLS measurements show that small micellelike aggregates are spontaneously formed above the cmc. Furthermore, carbonate-functionalized ILs were examined for their antimicrobial activity against a panel of clinically relevant microorganisms. Biological activity was found to increase with hydrophobicity. The presence of a carbonate ester moiety significantly enhances the antimicrobial efficiency as compared to nonfunctionalized ILs, with the susceptibility of Staphylococcus sp. toward the action of these compounds being particularly remarkable. It has been demonstrated that the functionalization of the alkyl side chain of the imidazolium salts can not only modify the aggregation behavior but also lead to differences in both efficiency and the spectrum of antimicrobial activity of amphiphilic ILs

Isolation and characterization of kurstakin and surfactin isoforms produced by Enterobacter cloacae C3 strain

In this work, the extraction, structural analysis, and identification as well as antimicrobial, anti‐adhesive, and antibiofilm activities of lipopeptides produced by Enterobacter cloacae C3 strain were studied. A combination of chromatographic and spectroscopic techniques offers opportunities for a better characterization of the biosurfactant structure. Thin layer chromatography (TLC) and HPLC for amino acid composition determination are used. Efficient spectroscopic techniques have been utilized for investigations on the biochemical structure of biosurfactants, such as Fourier transform infrared (FT‐IR) spectroscopy and mass spectrometry analysis. This is the first work describing the production of different isoforms belonging to kurstakin and surfactin families by E cloacae strain. Three kurstakin homologues differing by the fatty acid chain length from C10 to C12 were detected. The spectrum of lipopeptides belonging to surfactin family contains various isoforms differing by the fatty acid chain length as well as the amino acids at positions four and seven. Lipopeptide C3 extract exhibited important antibacterial activity against Gram‐positive and Gram‐negative bacteria, antifungal activity, and interesting anti‐adhesive and disruptive properties against biofilm formation by human pathogenic bacterial strains: Salmonella typhimurium, Klebsiella pneumoniae, Staphylococcus aureus, Bacillus cereus, and Candida albicans

Amino-acid-based surfactants: New antimicrobial agents

The rapid increase of drug resistant bacteria makes necessary the development of new antimicrobial agents. Synthetic amino acid-based surfactants constitute a promising alternative to conventional antimicrobial compounds given that they can be prepared from renewable raw materials. In this review, we discuss the structural features that promote antimicrobial activity of amino acid-based surfactants. Monocatenary, dicatenary and gemini surfactants that contain different amino acids on the polar head and show activity against bacteria are revised. The synthesis and basic physico-chemical properties have also been included

Green Catanionic Gemini Surfactant-Lichenysin Mixture: Improved Surface, Antimicrobial, and Physiological Properties

Catanionic surfactant mixtures form a wide variety of organized assemblies and aggregates with improved physicochemical and biological properties. The green catanionic mixture (NN omega)-N-alpha-Bis(N(alpha)caproylarginine) alpha,omega-propyldiamide (C-3(CA)(2)):Lichenysin (molar ratio 8:2) showed antimicrobial synergies against Yersinia enterocolitica, Bacillus subtilis, Escherichia coli O157:H7, and Candida albicans. Flow cytometry and viability studies indicated that this catanionic mixture increases the probability of Y. enterocolitica (38.2%) and B. subtilis (17.1%) cells entering a viable but nonculturable state. Zeta potential showed that one of the cationic charges of C-3(CA)(2) is neutralized by Lichenysin. An isotherm study demonstrated the formation of a stable aggregate between the two surfactants. The catanionic aggregate was able to interact with bacterial phospholipids. The lowest hemolysis (22.1 mu M) was obtained with the catanionic mixture, although an irritant potential (0.70) was characterized. According to the therapeutic index, the C-3(CA)(2):Lichenysin mixture was the formulation least toxic to eukatyotic cells. Partial neutralization of C-3(CA)(2) by Lichenysin modified the mode of action that enhances the transition of bacterial cells into a viable but nonculturable state (VBNC) and improved the cell selectivity. KEYWORDS:antimicrobial activity catanionic mixtures biosurfactant Lichenysin gemini surfactants flow cytometry VBNC Langmuir balanc

Lichenysin-geminal amino acid-based surfactants: Synergistic action of an unconventional antimicrobial mixture

Recently it has been demonstrated that catanionic mixtures of oppositely charged surfactants have improved physicochemical-biological properties compared to the individual components. Isotherms of mixtures of an anionic biosurfactant (lichenysin) and a cationic aminoacid surfactant (C-3(LA)(2)) indicate a strong interaction suggesting the formation of a new 'pseudo-surfactant'. The antimicrobial properties of the mixture lichenysin and C-3(LA)(2) M80:20, indicate a synergistic effect of the components. The mechanism of action on the bacterial envelope was assessed by flow cytometry and Transmission Electron Microscopy. (C) 2016 Elsevier B.V. All rights reserved. Keywords: Antimicrobial properties; Arginine; Escherichia coli; Flow cytometry; Gemini surfactants; Lichenysin; Listeria nonocytogenes; Potassium leakage; Transmission electron microscopy

New cationic vesicles prepared with double chain surfactants from arginine: role of the hydrophobic group on the antimicrobial activity and cytotoxicity

Cationic double chain surfactants have attracted much interest because they can give rise to cationic vesicles that can be used in biomedical applications. Using a simple and economical synthetic approach, we have synthesized four double-chain surfactants with different alkyl chain lengths (LANHCx). The critical aggregation concentration of the double chain surfactants is at least one order of magnitude lower than the CMC of their corresponding single-chain LAM and the solutions prepared with the LANHCx contain stable cationic vesicles. Encouragingly, these new arginine derivatives show very low haemolytic activity and weaker cytotoxic effects than conventional dialkyl dimethyl ammonium surfactants. In addition, the surfactant with the shortest alkyl chain exhibits good antimicrobial activity against Gram-positive bacteria. The results show that a rational design applied to cationic double chain surfactants might serve as a promising strategy for the development of safe cationic vesicular systems