Surface and Biocidal Properties of Gemini Cationic Surfactants Based on Propoxylated 1,6-Diaminohexane and Alkyl Bromides

Two new classes of gemini cationic surfactants—hexanediyl-1,6-bis[(isopropylol) alkylammonium] dibromide {in the abbreviation form: C_nC₆C_n[iPr-OH] and C_nC₆C_n[iPr-OH]₂; alkyl: C_nH_{2n + 1} with n = 9, 10, 12 and 14}—have been synthesized by interaction of alkyl bromides with N,N′-di-(isopropylol)-1,6-diaminohexane and N,N,N′,N′-tetra-(isopropylol)-1,6-diaminohexane. The surface tension, electrical conductivity, and dynamic light scattering (DLS) techniques were used to investigate the aggregation properties of the gemini cationic surfactants in aqueous solution. The formation of critical aggregates at two concentrations in an aqueous solution from obtained gemini cationic surfactants were determined via the tensiometric method. Thus, these gemini cationic surfactants start to form aggregates at concentrations well below their critical micelle concentrations (CMC). The surface properties and the binding degree (β) of the opposite ion were tested against the length of the surfactant hydrocarbon chain and the number of the isopropylol groups in the head group. By applying the DLS technique, it was explored that how the number of isopropylol groups in gemini cationic surfactants with C₁₂H₂₅ chain affects the sizes of micelles at concentrations greater than CMC. It was discovered that the obtained gemini cationic surfactants have a biocidal character.     

Synthesis, Surface Active and Thermodynamic Parameters of Novel Quaternary Ammonium Salts

Reactions of octanol, nonanol, decanol, and dodecanol with epichlorohydrin were carried out in the presence of sodium hydroxide as a catalyst. The synthesized non-ionic surfactants were modified with triethanolamine. Surface activity at the water-air interface and electrical conductivity of the resulting surfactants at 10, 20, 30 and 40?°C were determined and thermodynamic parameters of micellization and adsorption were calculated. It was established that the synthesized quaternary ammonium salts have the ability to localize thin crude oil films on the water surface formed due to spill.     

Synthesis and Characteristics of Dodecyl Isopropylolamine and Derived Surfactants

Dodecyl isopropylolamine has been synthesized on the basis of dodecylamine and propylene oxide. The structure of dodecyl isopropanolamine has been determined by X‐ray diffraction, elemental analysis, IR‐ and NMR‐spectroscopic methods. Ionic surfactants have been synthesized by interaction of dodecyl isopropylolamine with various acids (HCl, HBr, acetic and propionic) and alkyl halides (methyl iodide, ethyl bromide and n‐propyl bromide). Colloidal‐chemical parameters, petroleum‐collecting and petroleum dispersing capacities of the synthesized cationic surfactants have been studied.     

Electrical and Optical Properties of Unrelaxed InAs1 –xSbx Heteroepitaxial Structures

Semiconductors - The electrical and galvanomagnetic properties of unrelaxed heteroepitaxial InAs1 –xSbx structures (x = 0.43 and 0.38) in a wide temperature range of 5–300 K and...     

Synthesis and Properties of Quaternary Ammonium Surfactants Based on Alkylamine,Propylene Oxide,and 2‐Chloroethanol

New quaternary ammonium salts are synthesized by octylamine, nonylamine, dodecylamine, and hexadecylamine reacting with propylene oxide at a mole ratio of 1:2, followed by reaction with 2‐chloroethanol. By tensiometric measurements of aqueous solutions, their surface activity has been determined. Using the results of these measurements and electroconductometric studies, important parameters such as critical micelle concentration (CMC), efficiency of surfactant adsorption, surface pressure at the CMC, changes of Gibbs free energies for micelle formation, and adsorption were estimated. By application of the Gibbs adsorption isotherm, indices such as maximum surface excess concentration and minimum surface area/molecule at the air–water interface were also calculated. Petroleum‐collecting properties of these surfactants were investigated. Among these quaternary ammonium surfactants, the surfactant based on dodecylamine, propylene oxide, and 2‐chloroethanol exhibits the highest petroleum‐collecting capacity.     

Antimicrobial activity and safety of use of Enterococcus faecium PC4.1 isolated from Mongol yogurt

Screening of lactic acid bacteria strains isolated from Mongolian yogurt (Tarag) led to the isolation of Enterococcus faecium PC4.1 with a bacteriocin-like activity against Listeria genus and fungi. The antimicrobial substances in cell free supernatant were sensitive to proteolytic enzymes, while neither acidic conditions nor high temperature affected their activities. These antimicrobial substances were active after storage at 4 °C, ?20 °C and ?80 °C for over one month. The mode of action was determined as bactericidal. In the aim of further use of E. faecium PC4.1 as a biopreservative, the isolate was tested for resistance against antibiotics and for harboring virulence determinants. E. faecium PC4.1 was characterized as free from virulence factors, has low resistance to gentamicin and ampicillin but is susceptible to vancomycin.     

Proteolytic activities and safety of use of <Emphasis Type="Italic">Enterococci</Emphasis> strains isolated from traditional Azerbaijani dairy products

A collection of 147 isolates obtained from 23 samples of traditional Azerbaijani dairy products was screened for the presence of proteolytic enzymes. Six Enterococcus faecalis strains obtained from three cheese samples have been identified as proteinase-producing strains, according to their ability to hydrolyze caseins. RAPD–PCR profiles of their total DNA showed different patterns for strains isolated from different cheese samples. The proteolytic activities of these strains were studied during their growth in milk and in non-proliferative cells system. Isolated strains were able to hydrolyze α_S1-, α_S2-, β-caseins and BLG albeit to different extents, at optimal pH in the range 6.0–7.2 and optimal temperature in the range 37–45 °C, depending on the strain. Proteolysis was strongly inhibited in the presence of EDTA—specific inhibitor of metalloproteases—but the presence of other types of proteases cannot be excluded. The potential pathogenicity of the strains was evaluated investigating the presence of the genes coding different virulence factors and their resistance to antibiotics. The obtained results yield new information about technological characteristics and safety of studied Enterococci strains from Azerbaijani artisanal dairy products. Many from the isolated strains contribute certainly to the differences in flavor, texture, and taste of Azerbaijani traditional cheeses and could represent new adjunct cultures for the dairy industry.     

Counterion-coupled gemini (Cocogem) surfactants based on dodecylisopropylol amine and dicarboxylic acids: synthesis,characterization and evaluation as biocide against SRB

New cocogem surfactants were synthesized by interaction of dodecylisopropylol amine with dicarboxylic (oxalic, succinic, adipic, sebacic, tartaric, maleic, fumaric, isophthalic) acids. By tensiometric method, the surface activity of aqueous solutions of the synthesized cocogem surfactants at the border with air was studied and, by conductometric method, the specific electrical conductivity of these solutions was determined. The degree of counterion binding (β), critical micelle concentration (CMC), effectiveness of surface tension reduction (π_CMC), surface excess concentration (Γ_max), area per molecule at the interface (A_min), changes of Gibbs free energies of adsorption (ΔG_ad) and micellization (ΔG_mic) have been calculated. The character of change of the colloidal-chemical indices depending on spacer-group nature and length has been clarified. So, with an elongation of the spacer group and when passing from cis-form to trans-form, the value of CMC decreases. The obtained cocogem surfactants exhibit a considerable bactericidal effectiveness against sulfate-reducing bacteria. The bactericide properties of the cocogem surfactants containing in the spacer chain a saturated hydrocarbon fragment and benzene ring are stronger than for the others.     

Surface Activity,Thermodynamics of Micellization and Adsorption Properties of Quaternary Salts Based on Ethanolamines and Decyl Bromide

The surface-active properties of ionic-liquid type salts synthesized by the interaction of ethanolamines and decyl bromide have been studied. Surface tension as a function of concentration of the surfactant in aqueous solution was measured at 10, 20, 30 and 40 °C using a drop volume stalagmometer. From these measurements, the maximum surface excess concentration and the minimum area per molecule at the aqueous solution/air interface, the critical micelle concentration (CMC), the surface pressure at the CMC, and the standard thermodynamic parameters of adsorption and micellization were calculated. The structural effects on adsorption, micellization, and the effectiveness of surface tension reduction are discussed in terms of these parameters.     

Characterization of new strain Lactobacillus paracasei I-N-10 with proteolytic activity: Potential role in decrease in β-casein immuno-reactivity

The proteolytic activity of thirty-three LAB isolates from Mongolian tarag was tested on skimmed milk. The strain displaying the highest proteolytic activity was purified and presented by 16S rDNA sequencing 99.9?% homology with Lactobacillus paracasei 1-4-2A. It was named L. paracasei I-N-10. Proteases of L. paracasei I-N-10 hydrolyze predominately ??-casein and in some level ??_S2-casein; hydrolysis of ??_S1-casein was not observed. Proteolytic activity was optimal at 42?°C and neutral pH. Proteases of L. paracasei I-N-10 were inhibited by serine- and metalloproteases inhibitors. PCR amplification revealed the presence of prtP gene, which was identical to prtP gene of L. paracasei genus. Mass spectrometry analysis of ??-casein hydrolysate allowed to characterize 7 peptides resulting from proteolysis by L. paracasei I-N-10. The isolated strain was able to cleave ??-casein in different sites including 2 of the major linear epitopes implicated in its allergenicity. Being sensitive to main antibiotics classes, L. paracasei I-N-10 could be considered as safe and used as starter culture with a potential role in decreasing ??-casein immuno-reactivity.