Polyphenols and CRISPR as Quorum Quenching Agents in Antibiotic-Resistant Foodborne Human Pathogens (Salmonella Typhimurium, Campylobacter jejuni and Escherichia coli 0157:H7).

Antibiotic resistance in foodborne pathogens is an increasing threat to global human health. Among the most prevalent antibiotic-resistant bacteria are Salmonella enterica serovar Typhimurium, Campylobacter jejuni and E. coli 0157:H7. Control of these and other pathogens requires innovative approaches, i.e., discovering new molecules that will inactivate them, or render them less virulent without inducing resistance. Recently, several polyphenol molecules have been shown to possess such characteristics. Also, the use of CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) approaches has recently been proposed for such purpose. This review summarizes the main findings regarding the application of both approaches to control the above-mentioned foodborne pathogens by relying on Quorum Sensing interference (Quorum Quenching) mechanisms and highlights the avenues needed for further research.

Formulation of anomerization and protonation in d-glucosamine, based on 1H NMR.

The major anomer of non-protonated neutral d-glucosamine GlcN0 is the ß-form, while the α-anomer is dominant for protonated cationic glucosamine GlcNH+. The present work confirmed correlation between the anomerization and the protonation by simultaneous determination of signal intensity and chemical shift in pD-variation 1H NMR, and formulated the equilibrium constants between subspecies α-GlcN0, ß-GlcN0, α-GlcND+, and ß-GlcND+ to interpret the correlation. The individual anomerization constants, Kan = [ßGlcN]/[αGlcN] and KanD = [ßGlcND+]/[αGlcND+], are linked to each other through the relation KDα∙KanD = KDß∙Kan with the deuteration constants KDα and KDß of the anomers. The anomer populations are stimulated by OD- and D+ ions in the dose-response form. The acidic deuteron in α-GlcND+ is populated mostly at the nitrogen atom, whereas the population in ß-GlcND+ is comparable at nitrogen and anomeric oxygen; this difference is consistent with the basicity of the nitrogen and the anomerization process of glucosamine.

Mesoscopic Modeling of the Encapsulation of Capsaicin by Lecithin/Chitosan Liposomal Nanoparticles.

The transport of hydrophobic drugs in the human body exhibits complications due to the low solubility of these compounds. With the purpose of enhancing the bioavailability and biodistribution of such drugs, recent studies have reported the use of amphiphilic molecules, such as phospholipids, for the synthesis of nanoparticles or nanocapsules. Given that phospholipids can self-assemble in liposomes or micellar structures, they are ideal candidates to function as vehicles of hydrophobic molecules. In this work, we report mesoscopic simulations of nanoliposomes, constituted by lecithin and coated with a shell of chitosan. The stability of such structures and the efficiency of the encapsulation of capsaicin, as well as the internal and superficial distribution of capsaicin and chitosan inside the nanoliposome, were analyzed. The characterization of the system was carried out through density maps and the potentials of mean force for the lecithin-capsaicin, lecithin-chitosan, and capsaicin-chitosan interactions. The results of these simulations show that chitosan is deposited on the surface of the nanoliposome, as has been reported in some experimental works. It was also observed that a nanoliposome of approximately 18 nm in diameter is stable during the simulation. The deposition behavior was found to be influenced by a pattern of N-acetylation of chitosan.

Seasonal Effect on the Biological Activities of Litsea glaucescens Kunth Extracts.

This study shows the seasonal effect on the antioxidant, antiproliferative, and antimicrobial activities of L. glaucescens Kunth (LG) leaves extracts. Their antioxidant activity was evaluated through the DPPH, FRAP, and ORAC assays. Their phenolic content (PC) was determined by means of the Folin-Ciocalteu method, and the main phenolic compounds were identified through a HPLC-DAD analysis. Antiproliferative activity was determined by MTT assay against HeLa, LS 180, M12.C3.F6, and ARPE cell lines. Antimicrobial potential was evaluated against Staphylococcus aureus and Escherichia coli using a microdilution method. All the LG extracts presented high antioxidant activity and PC, with quercitrin and epicatechin being the most abundant. Antioxidant activity and PC were affected by the season; particularly autumn (ALGE) and summer (SULGE) extracts exhibited the highest values (p < 0.05). All extracts presented moderate antiproliferative activity against the cell lines evaluated, HeLa being the most susceptible of them. However, ALGE and SULGE were the most active too. About antimicrobial activity, SULGE (MIC90 < 800 µg/mL; MIC50 < 400 µg/mL), and SLGE (MIC50 < 1000 µg/mL) showed a moderate inhibitory effect against S. aureus. These findings provide new information about the seasonal effect on the PC and biological properties of LG extracts. Clearly, antioxidant activity was the most important with respect to the other two.

1H NMR studies of molecular interaction of D-glucosamine and N-acetyl-D-glucosamine with capsaicin in aqueous and non-aqueous media.

Complex formation of D-glucosamine (Gl) and N-acetyl-D-glucosamine (AGl) with capsaicin (Cp) were studied by 1H NMR titrations in H2O-d2 and DMSO-d6; capsaicin is the major bioactive component of chili peppers. Every titration curve has been interpreted by formulating a suitable model for the reaction equilibrium, to elucidate intermolecular interactions. In DMSO, glucosamine cations associate with each other to yield linear aggregates, and undergo pseudo-1:1-complexation with capsaicin, the formation constant being ca. 30 M-1. N-Acetylglucosamine, without self-association, forms a 2:1-complex AGl2Cp with the stability of ca. 70 M-2. These complexations are achieved by intermolecular hydrogen bonds. In D2O, glucosamine undergoes reversible protonation equilibrium between Gl0 and GlH+ with the logarithmic protonation constants log KD = 8.63 for α-glucosamine and 8.20 for ß-isomer. Both anomeric isomers of deprotonated glucosamine form Gl0Cp-type complexes of capsaicin, in a competitive manner, with a formation constant of 1040 M-1 for the α-glucosamine complex and 830 M-1 for the ß-complex; the anomeric carbons result in the difference in thermodynamic stability. The reactant molecules are closed up by the solvent-exclusion effect and/or the van der Waals interaction; the resulting pair is stabilized by intermolecular hydrogen bonding within a local water-free space between the component molecules. By contrast, neither protonated glucosamine (GlH+) nor N-acetylglucosamine yields a capsaicin complex with the definite stoichiometry. The monosaccharides recognize capsaicin under only a controlled condition; the same phenomena are predicted for biological systems and nanocarriers based on polysaccharides such as chitosan.

Physical Characteristics of the Leaves and Latex of Papaya Plants Infected with the Papaya meleira Virus.

Sticky disease, which is caused by Papaya meleira virus (PMeV), is a significant papaya disease in Brazil and Mexico, where it has caused severe economic losses, and it seems to have spread to Central and South America. Studies assessing the pathogen-host interaction at the nano-histological level are needed to better understand the mechanisms that underlie natural resistance. In this study, the topography and mechanical properties of the leaf midribs and latex of healthy and PMeV-infected papaya plants were observed by atomic force microscopy and scanning electron microscopy. Healthy plants displayed a smooth surface with practically no roughness of the leaf midribs and the latex and a higher adhesion force than infected plants. PMeV promotes changes in the leaf midribs and latex, making them more fragile and susceptible to breakage. These changes, which are associated with increased water uptake and internal pressure in laticifers, causes cell disruption that leads to spontaneous exudation of the latex and facilitates the spread of PMeV to other laticifers. These results provide new insights into the papaya-PMeV interaction that could be helpful for controlling papaya sticky disease.

Determination of chitin and protein contents during the isolation of chitin from shrimp waste.

Accurate determination of chitin and protein contents in crustacean biomass and the intermediate products during the industrial isolation of chitin cannot be made directly from the total nitrogen content, unless the appropriate corrections are applied. This method, however, is affected by the presence of other nitrogen-containing chemical species that are formed endogenously or by the action of microorganisms during the handling of the sample. Therefore, an alternative rapid method to estimate the contents of these components can be very useful both in research and in various fields of application. An original method has been developed to address this problem. The method consists of the development of a set of equations based on the stoichiometric contents of nitrogen of chitin and protein whereby the amounts of each component can be estimated from the value of the total nitrogen content, provided the rest of the proximate composition of the sample is accurately known. In order to validate the procedure, a set of model mixtures of pure chitin and protein concentrate in the solid state, both extracted from shrimp head waste, are used. Excellent agreement between the predicted and real values of chitin and protein are obtained (R2=0.98, slope=0.90). When the proposed method is tested in the analysis of real samples obtained from five different processing protocols of pretreatment of raw shrimp head, it is found that in general the values of protein and chitin contents throughout the various stages of the process vary as expected. [GRAPH: SEE TEXT] Variation of the measured total nitrogen versus calculated stoichiometric total nitrogen of the chitin-protein mixtures.

Molecular cloning of a beta-glucan pattern-recognition lipoprotein from the white shrimp Penaeus (Litopenaeus) vannamei: correlations between the deduced amino acid sequence and the native protein structure.

The hemolymph pattern-recognition beta-glucan binding protein from the white shrimp Penaeus (Litopenaeus) vannamei is also a high density lipoprotein (betaGBP-HDL) involved in innate immunity. The betaGBP-HDL full length cDNA sequence determined was 6.3 kb long, and contains a long 3'UTR region with a polyadenylation signal and a poly-A+ tail. The open reading frame is 1454 amino acids long and the N-terminal residue of the mature protein is localized in position 198 of the ORF. Comparison of the betaGBP-HDL amino acid sequence against GenBank detected only significant similarity to betaGBP from the crayfish Pacifastacus leniusculus. betaGBP-HDL is expressed in hepatopancreas, muscle, pleopods and gills, but not in hemocytes as determined by RT-PCR. We discuss the analysis of the deduced primary sequence in terms of the predicted secondary structure, glucanase-like and RGD motives relevant to its dual roles in defence and lipid transport.

Biophysical evidence of lipid and carbohydrate binding activities of shrimp high density lipoprotein/beta glucan binding protein.

Crustacean High Density Lipoprotein/beta-Glucan Binding Protein (HDL/BGBP) has been studied due to its role in nutrition and immune response via activation of the defense cells (hemocytes) upon binding 1,3-D-beta-glucan carbohydrates. In this study, HDL/BGBP was found to be composed mainly of beta sheets, as determined by circular dichroism. Lipoprotein aggregation resulted when HDL/BGBP interacted with phospolipid vesicles, laminaribiose (1,3-beta-glucan disaccharide) or heparin. HDL/BGBP has similar dissociation constants for laminaribiose (K(d)=22 mM) or heparin (K(d)=46 mM) as determined by 90 degrees light scattering.

Conservación y estabilidad de la tortilla de maíz a temperatura ambiente / Preservation and stability of corn turtledove at room temperature

Se estudiaron cuatro conservadores químicos para estabilizar tortilla de maíz a temperatura ambiente (25ºC); propionato de sodio, combinación de sorbato de potasio-metilparabén y metilparabén-peróxido de hidrógeno. Se realizó un estudio de almacenamiento y estabilidad con el conservador que arrojó mejores resultados, para lo cual se seleccionaron dos materiales de empaques: Papel y Polietileno de Alta Densidad. La calidad de la tortilla durante su almacenamiento fue evaluada en función de la humedad, análisis microbiológico (recuento de mesófilos, hongos y levaduras) y evaluación sensorial. Los resultados se analizaron por medio de un análisis de covarianza y contraste de pendientes entre empaques, adoptando un nivel de significancia de p<0.05. El deterioro de la calidad organoléptica de la tortilla sin conservador, se asoció con una elevada cuenta de bacterias gram negativas, hongos y levaduras responsables de los olores ofensivos en 24 horas o menos. De los conservadores estudiados, la mezcla de metilparabén-peroxido de hidrógeno fue el único conservador que tuvo un efecto significativo, tanto sobre las bacterias como sobre los hongos y levaduras, retardando el deterioro microbiano. además, no se detectaron residuos de peróxido de hidrógeno en el producto después de dos días de almacenamiento. Los resultados de estudios de almacenamiento y estabilidad utilizando esta mezcla, reafirman la inconveniencia del uso de papel para prevenir cambios de textura y humedad en la tortilla aún cuando se almacena por períodos cortos. Además, el uso de metilparabén y peróxido de hidrógeno puede permitir conservar la tortilla de maíz en condiciones aceptables para el consumidor hasta por un período de seis días a temperatura ambiente, lo cual podría influir significativamente en las prácticas actuales de comercialización.

Efecto del material de empaque y temperatura de almacenamiento en la calidad de la tortilla de maíz / Effect of packing material and temperature of storage in quality of maize tortilla

Se seleccionaron tres materiales (papel, polietileno de baja densidad y polietileno de alta densidad) para empacar tortilla de maíz comercial y conservarla a temperaturas de refrigeración (5§C) y congelación (-10§C). La calidad de la tortilla durante su almacenamiento se evaluó por medio de pH, húmeda, textura (resistencia al corte, resistencia a la punción en centros y extremos), y por pruebas sensoriales. Los resultados se analizaron valiéndose de ananálisis de covarianza y contraste de pendientes entre tratamientos, y adoptando un nivel de significancia de P<0.05. A -10§, la calidad de la tortilla se mantuvo sin cambios significativos durante los 11 días de almacenamiento, sin que se presentaran diferencias objetivas entre empaques. En cambios, a los 5§C, la tortilla empacada en papel perdió 6.8% de su humedad original. Debido a esto, a los 11 días el panel sensorial encontró el producto inaceptable por razones de textura y aroma. A esta temperatura, los polietilenos de baja y alta densidad fueron igualmente efectivos para conservar una calidad superior a la empacada en el papel tradicional de despacho. Las pruebas de textura mostraron que ...