This study was conducted to identify and evaluate the antimicrobial activity of some Lactobacillus isolates of chicken origin. Among 90 isolates 14 Lactobacillus species were distinguished using MALDI-TOF mass spectrometry and 16S-ARDRA. The dominant species was L. salivarius (34.4%), followed by L. johnsonii (23.3%), L. crispatus (13.3%) and L. reuteri (11.1%). All lactobacilli were screened for antimicrobial activity against wild-type strains of Salmonella enterica, Escherichia coli, and Clostridium perfringens. Results from the agar slab method showed that all Lactobacillus isolates were able to produce active compounds on solid media with antagonistic properties against these pathogens. The highest sensitivity to lactobacilli was observed in C. perfringens strains, and the lowest in E. coli. Lactobacillus salivarius exhibited particularly strong antagonism towards all of the indicator bacteria. Strains of L. ingluviei and L. johnsonii and one strain of L. salivarius (10d) selectively inhibited the growth of C. perfringens. No antimicrobial activity of many Lactobacillus isolates was observed when cell-free culture supernatant was used in a well diffusion assay. All Lactobacillus isolates exhibited the ability to produce H2O2 and proved to be hydrophobic (excluding one of L. salivarius). [Int Microbiol 19(1):57-67 (2016)]Keywords: Lactobacillus spp. · avian lactobacilli · antimicrobial activity · gut health · poultry pathogens

Antimicrobial activity of

Esterification of free fatty acids in waste cooking oils (WCO): Role of ion-exchange resins

The Physical Chemistry of Electrolytic Solutions.

Influence of solvent selection and extraction temperature on yield and composition of lipids extracted from spent coffee grounds

Free fatty acids (FFA) are produced by the hydrolysis of oils and fats. The level of FFA depends on time, temperature and moisture content because the oils and fats are exposed to various environments such as storage, processing, heating or frying. Since FFA are less stable than neutral oil, they are more prone to oxidation and to turning rancid. Thus, FFA is a key feature linked with the quality and commercial value of oils and fats. The American Oil Chemists' Society (AOCS), the Association of Official Analytical Chemists (AOAC) and the European Commission (EC) Regulations have established almost identical standard methods for the assessment of FFA. These methods are based on titration, where oils or fats need to be dissolved in hot neutralized ethanol or ethanol/diethyl ether using phenolphthalein as an end point indicator. Titrimetric procedures are, however, laborious and need large amounts of chemicals and solvents. The cost of chemicals and environmental issues further limit these procedures. In addition, accurate detection of end points, especially for highly colored crude oil using a colorimetric indicator, is a difficult task. Despite these disadvantages, the titration method is unfortunately still being used in most of the edible-oil industries for the determination of FFA. Because of a lack of any comprehensive review on this very important topic, we have made an attempt to present a review in order to discuss the various methods available with special emphasis on the instrumental methods because of their high sensitivity, accuracy and rapidity.

Analytical approaches for the assessment of free fatty acids in oils and fats

A new method of acid value determination in vegetable oils has been developed. The method is based on (a) simple, rapid and complete extraction of acids from an oil test portion into reagent (0.05 mol dm - 3 triethanolamine (B) in the mixture of 50 % H 2 O + 50 % 2-PrOH) and (b) indirect titration of acids in BH + form against aqueous alkali in the presence of a phenolphthalein indicator. Suitable metrological parameters of acid value determination have been obtained. The advantages of the method are (i) absence of a toxic solvent, (ii) extraction and titration of acids at room temperature, and (iii) no need for preliminary neutralization of acid admixtures in a solvent.

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Acid Value Determination in Vegetable Oils by Indirect Titration in Aqueous-alcohol Media

A model of electrode reaction preceded by a first-order chemical reaction under chronoamperometric conditions on spherical electrodes has been developed. A general solution applying to all values of equilibrium constants, including very small ones, was obtained by numerical integration. Well-known analytical solutions for steady-state and near-steady-state conditions and for pure kinetic currents were shown to be special cases of the general solution. The conditions for their application are given.

/pdf/a-model-of-ce-mechanism-on-spherical-electrodes-tyr5o8w1ls.pdf

A Model of CE Mechanism on Spherical Electrodes

Equilibrium constants of the glyoxylic acid hydration have been defined more precisely taking into account the values of the DC polarographic limiting kinetic current and the dimerization effect. For the correct calculation of the rate constants for the glyoxylic acid dehydration and recombination reactions, the diffusion contribution of the dehydrated anions into the limiting kinetic current of the first and total DC polarographic waves was considered and the concept of the preceding consecutive rate determining reactions of the dehydration and recombination was used. The rate constants from the DC polarographic data have been obtained that are close to the ones from the pulse polarographic and spectrophotometric data. On the basis of a comparison with the linear-sweep voltammetric data, intermolecular catalysis of the dehydration reaction was noted. The recombination stage corresponds to protonation of the carboxylate group. The fast intramolecular protonation of the carbonyl group after the recombination stage has been considered.

/pdf/kinetics-and-equilibrium-of-the-dehydration-hydration-and-66ull8j9ja.pdf

Kinetics and Equilibrium of the Dehydration-Hydration and Recombination-Dissociation Reactions of Glyoxylic Acid Investigated by Electrochemical Methods

Preceding chemical reactions in dc polarography:: different approaches to the analysis of the carbonyl compounds dehydration kinetics

New analyses of the kinetics of the dehydration reaction of pyruvic acid and ethyl pyruvate gem-diol group have been performed using the direct current polarographic data. The diffusion contributions of the depolarizer (as keto-form) from the bulk solution to the total limiting kinetic and diffusion currents have been taken into account. As a result, corresponding equations for the kinetic current and for the thickness of the reaction layer have been obtained. It was shown that the condition of the stationarity of the diffusion and chemical reactions is carried out that is necessary for using the equation of the kinetic current. The values of the rate constants of the dehydration of the gem-diol group calculated by us were close to the ones found by other methods. Detailed analyses of the hydration equilibrium constants of the pyruvic acid keto-group allowed us to choose the most correct constants for kinetic calculations.

/pdf/studying-kinetics-of-the-dehydration-reaction-of-pyruvic-4b8txdn1ep.pdf

Yakov I. Tur'yan

Papers

Acid Value Determination in Vegetable Oils by Indirect Titration in Aqueous-alcohol Media

A Model of CE Mechanism on Spherical Electrodes

Kinetics and Equilibrium of the Dehydration-Hydration and Recombination-Dissociation Reactions of Glyoxylic Acid Investigated by Electrochemical Methods

Preceding chemical reactions in dc polarography:: different approaches to the analysis of the carbonyl compounds dehydration kinetics

Studying Kinetics of the Dehydration Reaction of Pyruvic Acid and Ethyl Pyruvate Using the Polarographic Kinetic Currents