Further analysis of the antimicrobial activity of α-phenylseleno citronellal and α-phenylseleno citronellol

In this work we performed studies on the antimicrobial activities of α-phenylseleno citronellal and α-phenylseleno citronellol, two new selenium-containing citronella oil derivatives. The presence of phenylselenium group in the citronellal molecule increased antimicrobial activity, as compared to a natural, unsubstituted terpene. We assessed the antimicrobial activity of each compound against three important species of foodborne pathogenic bacteria: Listeria monocytogenes, Staphylococcus aureus and Salmonella Typhimurium, using the agar diffusion method and by measuring the minimum inhibitory concentration, all the tested compounds showed antimicrobial activity against the three bacteria used. The modified aldehyde showed good values of a minimum inhibitory concentration of 0.03 mM and antimicrobial activity against Salmonella Typhimurium at 6.400 arbitrary units per milliliter (AU/mL). The identification of the antimicrobial properties of compounds derived from citronella suggests that the use of these substances to protect food against pathogenic bacteria deserves further exploration.     

Antimicrobial activity of açaí against Listeria innocua

A study was carried out to evaluate antimicrobial activity of açaí against Listeria innocua, as a non-pathogenic surrogate for Listeria monocytogenes, at different temperatures (37, 22, and 10 °C), from a kinetic point of view. With this aim, first the Minimum Inhibitory Concentration (MIC) under optimal growth conditions was established (37 °C), and then the effect of 3 non-inhibitory doses (3, 5, and 7 g/L) at 37, 22, and 10 °C was evaluated on the basis of the kinetic parameters lag time (λ) and maximum specific growth rate (μ_max). The Total Phenolic Content (TPC) of the samples tested as a function of açaí concentration was also determined. Results obtained showed that the MIC was 10 g/L, containing 2154.91 ± 126.10 mg of Gallic Acid Equivalents (GAE)/L. At non-inhibitory doses, regardless of temperature, the higher the açaí concentration, the higher the value of λ, and the effect of a variation in açaí concentration on λ was greater at high temperatures. Therefore, the addition of non-inhibitory doses of açaí could provide a means of controlling the growth of L. monocytogenes if a cold chain failure occurs, or if any other reason compromises the microbiological safety of minimally processed foods. Consequently, the present study is important both for the science community and for the food industry because it provides the first mathematical characterization of açaí antimicrobial activity and reveals its potential use to control the concentration and growth of pathogenic bacteria in foods free of non-synthetic additives.     

Assessment of antimicrobial activity of Nα -lauroyl arginate ethylester (LAE®) against Yersinia enterocolitica and Lactobacillus plantarum by flow cytometry and transmission electron microscopy

N^α -lauroyl arginate ethylester, LAE^®, which was approved as GRAS by the US Food and Drug Administration (FDA) and by the European Food Safety Authority (EFSA) in 2007, is a surfactant that exhibits antimicrobial activity. To assess its antimicrobial effect, treated cell suspensions of Yersinia enterocolitica and Lactobacillus plantarum were analysed for reduction of cell viability. Membrane dysfunction was determined by staining with bis-oxonol to detect the loss of membrane potential, and with propidium iodide to detect permeabilized membranes by flow cytometry. LAE^® treatment for 30 min induced a 4 log₁₀ reduction in cell viability in both bacteria; different subpopulations with variable degrees of cellular damage were observed by flow cytometry. Permeabilized membranes suggested the leakage of cellular material; this was also indicated by the loss of potassium ion(s), which was higher in L. plantarum than in Y. enterocolitica. Structural changes involving collapse of the cytosol and alterations of the cellular envelopes, mainly in Y. enterocolitica, and the formation of mesosomes in L. plantarum were observed by transmission electron microscopy.     

Antibacterial characteristics and mechanisms of ɛ-poly-lysine against Escherichia coli and Staphylococcus aureus

The aim of this study was to investigate the antibacterial characteristics and antibacterial mechanisms of ɛ-poly-lysine against Escherichia coli and Staphylococcus aureus. The diameters of inhibition zones of E. coli (10 ± 0.5 mm) and S. aureus (12 ± 0.1 mm) treated by 200 μg/ml ɛ-poly-lysine were much larger than control (5 ± 0.3 mm) (p < 0.05). Minimum inhibition concentration of ɛ-poly-lysine against E. coli and S. aureus was 12.5 μg/ml. Scanning electron microscopy showed that ɛ-poly-lysine damaged the morphology of tested bacterial cells. The increase in electric conductivity of bacterial cells suspension indicated that the cytoplasmic membranes were broken by ɛ-poly-lysine, which caused leakage of ions in cells. SDS-PAGE of bacterial proteins demonstrated that ɛ-poly-lysine could damage bacterial cells through the destruction of cellular proteins. These results indicated that ɛ-poly-lysine has good potential to be as a natural food preservative.     

Synthesis,characterization and comparative study of nano-Ag–TiO2 against Gram-positive and Gram-negative bacteria under fluorescent light

Currently, some of the major problems affecting the world are air pollution as well as microbial contamination. Every time we breathe, we are risking our lives by inhaling dangerous chemicals and biological contaminants that have found their way into the air. Therefore this work focuses on the antibacterial activity of Ag–TiO₂ to overcome the microbial contaminant and infectious disease. Ag–TiO₂ nanosolution were synthesized by sol–gel method and found to be an effective visible light driven photocatalyst. The nanosolutions were characterized by X-ray diffraction (XRD), transmittance electron microscopy (TEM), photoluminescence (PL) spectra, and X-ray photoelectron spectroscopy (XPS). At the concentration of 0.2–0.1 M, Ag–TiO₂ caused 100% inhibition of bacterial growth. The antibacterial efficacy of Ag–TiO₂ was evaluated with two kinds of bacteria; Gram-positive and Gram-negative. The colony count of Ag–TiO₂ against Gram-negative were evaluated with stain such as Escherichia coli, Pseudomonas aeruginosa and Shigella while for Gram-positive were investigated with Staphylococcus aureus, Bacillus subtilis, Bacillus cereus. Colony count results indicated that Ag–TiO₂ able to kill bacteria at the lowest concentration of 0.05 M that contains 0.06 mol % Ag. From the SEM and TEM observation, the survival of the Gram-positive was low and the decomposition was rapid as compared to Gram-negative bacteria.     

Screening for potential new probiotic based on probiotic properties and α-glucosidase inhibitory activity

In this study, 11 lactic acid bacteria (LAB) strains were screened for potential new probiotics using in vitro methods, including acid and bile salt tolerance, adhesion, antioxidative and α-glucosidase inhibitory activity. The results indicated that Lactobacillus casei 2W and Lactobacillus rhamnosus Z7 showed better potential probiotic properties and α-glucosidase inhibitory activity in vitro. The characteristics of L. casei 2W were better than those of L. rhamnosus GG, and L. rhamnosus Z7 was the most similar strain to L. rhamnosus GG, which had an antidiabetic capability. This finding suggested that L. casei 2W and L. rhamnosus Z7 could be used as potential antidiabetic probiotics. Further research is required to examine the α-glucosidase inhibitory activity of these strains.     

The antimicrobial effects and synergistic antibacterial mechanism of the combination of ε-Polylysine and nisin against Bacillus subtilis

The aim of the present study was to evaluate the combined effects of ε-Polylysine (ε-PL) and nisin and investigate the synergistic action of these compounds against Bacillus subtilis (B. subtilis).The combination of ε-PL and nisin showed synergistic anti-microbial activity against Escherichia coli (E. coli), B. subtilis and Staphylococcus aureus (S. aureus). SEM and TEM microscopy revealed that combined treatment with ε-PL and nisin synergistically damaged the morphology of tested bacterial cells. Propidium iodide (PI) infiltration experiments indicated that combined treatment with ε-PL and nisin synergistically enhanced the permeability of the bacterial cell membrane, likely reflecting the inhibition of both Na⁺K⁺- and Ca⁺⁺ Mg⁺⁺-ATPase activities through these compounds. The fluorescence spectrum showed an interaction between ε-PL and DNA, but not between nisin and DNA. The mode of ε-PL in binding with DNA was similar to that of ethidium bromide (EB). These results indicated that the uptake of ε-PL into cells was promoted through nisin, and subsequently, ε-PL interacted with the intracellular DNA achieving a synergistic effect.     

Assessment of and Countermeasures against International Political Risk for Chinese Oil Companies

1. International political risks in oil business Political risk is the possibility of the business environment getting worse due to political forces, affecting the profits of companies and their business goals. Oil is an important strategic resource, and is closely related to politics. Each political factor has a significant impact directly on petroleum industry. Therefore, petroleum industry is vulnerable to high political risks. Oil companies will suffer losses in their business or fail in …     

Synthesis Antimicrobial Activity of p-Dimetyl-Amino-Benyzlaldehide Shift Base of α-NaftyI-Amine and Metal Complexes

A new Shift bases was synthesized by the reaction of p-dimetyl-amino-benzylaldehide and α-naftyl-amine. All synthesized compounds were characterized by elemental analysis, IR （infra red） spectroscopy and NMR （nuclear magnetic resonance） spectroscopy and evaluated for their in vitro antifungal activities of the compounds tested against Pseudomonas aeruginosa, Mycobacterium lacticolium, Aspergillus niger, Cladasporium resinale, Penicillium chrosegenum, Chastorniurn gloloodium and Trichoderma virideh. These derivatives have vast range of biological activities which benefit us.     

Synergistic effect of gold and copper in the catalytic conversion of ethanol to linear α-alcohols

The reaction features of the direct conversion of ethanol to butanol-1 and hexanol-1 in the presence of mono- and bimetallic active components based on Au and Cu supported on γ-Al₂O₃ have been studied. It has been found that under conditions providing the supercritical state of ethanol, the reaction rate and selectivity in the presence of the Au–Cu/Al₂O₃ catalyst abruptly increases. In addition, a synergistic effect is observed: the yield of desired products over the Au–Cu catalyst is 6 or 14 times that over the Au or Cu monometallic counterpart, respectively. Differences in the catalytic behavior of the Au–Cu, Au-, and Cu-based systems have been discussed taking into account their structural features and the reaction mechanism.     

Fast determination of α- and β-thujone in alcoholic beverages using solid-phase extraction and gas chromatography

Determination of α- and β-thujone concentration in various foodstuffs is of great importance due to their antagonistic action against GABA receptors. The present study describes a fast, simple and sensitive method of α- and β-thujone analysis in alcoholic beverages using gas chromatography combined with solid phase extraction (SPE). The developed method is characterized by: high yield (above 98%); and low sufficient detection limit 0.033 mg/L; high precision (RSD below 1.8%); excellent linearity for α- and β-thujone performed in the concentration range 5.0-300.0 mg/L for α-thujone and 0.5-30.0 mg/L for β-thujone with R² = 0.9995 and R² = 0.9992, respectively. The presented analytical approach constitutes substantial improvement on the previously reported methods, which involve solvent consuming liquid-liquid extraction or less selective and difficult to calibrate solid phase micro-extraction (SPME).     

Biodiversity,dynamics and antimicrobial activity of lactic acid bacteria involved in the fermentation of maize flour for doklu production in Côte d'Ivoire

Doklu is a maize-based spontaneously fermented dough produced and consumed in parts of West Africa, particularly in Côte d'Ivoire. The characterization of the microbial ecosystem of doklu was carried out using a polyphasic approach. First, culture-dependent methods were used for bacterial enumeration and the phenotypic and molecular identification of 250 lactic acid bacteria (LAB) isolates. Then, culture-independent methods, including PCR-TTGE (V3 region of the 16S rRNA gene), provided a fingerprinting of bacterial DNA directly extracted from doklu. Bio preservative abilities were also tested and strains producing antimicrobial compounds were genotyped using PFGE. During maize dough fermentation, LAB became dominant and their load increased from 4.2 ± 0.2 log CFU/g to 9.0 ± 0.7 log CFU/g only after 48 h. Culture-dependent methods highlighted the presence of five LAB groups with the species Lactobacillus plantarum (28%), Lactobacillus fermentum (41.6%), Pediococcus acidilactici (6.8%), Pediococcus pentosaceus (18%) et Weissella cibaria (5.6%), succeeding during the fermentation. Lb. fermentum being practically the only species present at the end of fermentation, is with Lb. plantarum, the predominant species of fermenting dough. Culture-independent analysis underlined the undoubted role of Lb. fermentum, actively involved in the dough fermentation. These Lb. fermentum species, with a diversity of strains also showed important antimicrobial activity, due to production of bacteriocins. Being able to produce antimicrobial compounds, Lb. fermentum species may act as both bio protective culture as well as fermenting agent in cereal products and could be exploited to create functional starter cultures.     

Modified mesoporous catalysts based on Al-HMS and Al-MCF for the oligomerization of α-olefins

High-performance decene-1 oligomerization catalysts based on mesoporous Al-HMS and Al-MCF aluminosilicates modified with an F-4SF sulfonated perfluorinated copolymer have been synthesized. Under batch conditions with a conversion of 90% and in a flow system with a conversion of 83%, these catalysts provide the formation of an oligomerization product with viscosity properties characteristic of poly-α-olefins, the precursors of poly-α-olefin oils.     

Influence of variety and growth environment on β-amylase activity of flour from sweet potato (Ipomea batatas)

In order to select a suitable Ghanaian variety of sweet potato as enzyme source for the production of glucose syrups, four varieties of sweet potatoes – Sauti, Santom pona, Faara and Okumkom – cultivated in two different agro-ecological zones of Ghana were evaluated for β-amylase activity. Faara and Okumkom varieties harvested at 5 months maturity from the forest zone showed the highest β-amylase activity and consequently the most suitable potential enzyme source for the hydrolysis of starchy materials in glucose syrup production. Enhancing β-amylase levels in sweet potatoes has potential cost efficiency advantages in glucose syrup production.     

Corrosion inhibition of α,β-unsaturated carbonyl compounds on steel in acid medium

Corrosion inhibition of three α,β-unsaturated carbonyl compounds on N80 steel at high temperature and in concentrated acid medium was evaluated, and the inhibition mechanism was investigated. The results proved that both cinnamaldehyde and benzalacetone had an evident anticorrosion effect and could reduce the corrosion of steel effectively in acid medium, α,β-unsaturated carbonyl compounds with a benzene ring structure had good adsorption on steel surface. The experiments proved that polymerization of α,β-unsaturated carbonyl compounds on the steel surface at a high temperature and in concentrated acid medium resulted in a good corrosion inhibiting effect, which was attributed to the structures of α,β-unsaturated carbonyl compounds.     

Effects of Desensitizers on Phase Transitions,Thermal Behavior,and Sensitivity of ε-CL-20

The phase transitions of ε-CL-20 coated with desensitizers [paraffin wax (PW), microcrystal wax (MW), graphite, molybdenum disulfide, tungsten disulfide, and graphite fluoride] were investigated using powder X-ray diffraction (PXRD) and differential scanning calorimetry (DSC). The thermal behavior of ε-CL-20 and ε-CL-20 coated with desensitizers was analyzed, and the compatibility of ε-CL-20 with the desensitizers was assessed using vacuum stability tests. The characteristics of several desensitizers were measured, and their effects on the friction and impact sensitivity of coarse and fine ε-CL-20 crystals were analyzed. The results indicate that graphite decreased the critical temperature of phase transition. The phase transition of DSC results is consistent with the PXRD data. ε-CL-20 was compatible with all the desensitizers studied. Molybdenum disulfide markedly lowered the impact sensitivity; PW and MW lowered the friction sensitivity of ε-CL-20. The molybdenum disulfide/PW compound system reduced both the friction and impact sensitivity of ε-CL-20.     

Role of Structure and Acidic Nature on Catalytic Behavior of Nickel Supported H-mordenite,H-ZSM-5, and γ–alumina Catalysts

Abstract

Nickel metal was loaded in different percentages (7, 10, and 13% w/w) on different supports (H-mordenite, H-ZSM-5, and γ–alumina). The prepared catalyst samples were tested in cyclohexane conversion using microreactor pulse technique. Structure was followed up by XRD analysis. Chemisorption of tert-butylamine (TBA) was adopted for estimating the number of surface acid sites. It was found that all prepared samples displayed cracking activity, being mostly related to the fraction of acid sites remaining on the surface after coverage with supported Ni atoms. H-mordenite-supported samples exhibited mainly isomerization functionality by showing a larger portion of surface acid sites. H-ZSM-5-supported samples showed higher dehydrogenation activity. Agglomeration seemed to be responsible for lower activity of the sample of higher Ni content. The formed NiOOH phase was suggested to be responsible for increased dehydrogenation activity on H-ZSM-5 samples and increased cracking activity on γ–alumina-supported samples of higher Ni content.