Changes of the cell surface hydrophobicity of Lactobacillus acidophilus La‐5 in response to pH,temperature and inulin

The main topic of this study was to study how cell surface hydrophobicity (CSH) could change in response to pH, temperature and inulin; Lactobacillus acidophilus La‐5 was used as a model microorganism. pH, temperature, inulin and incubation time (exposure to prebiotic or incubation at pH 4.0 and 9.0) were combined through a full factorial design and a Central Composite Design; the results were analysed using a multifactorial anova (first step) and a stepwise regression (second step). Temperature and pH significantly affected CSH: an increase in the temperature determined a significant increase in CSH, whereas the correlation pH vs. CSH was negative, as an increase in pH caused a significant decrease in CSH. Inulin played a significant role, but its effect could be influenced by temperature, pH and exposure time. This study is the first approach on the effects of some environmental factors on CSH and suggests that the culturing conditions and/or the exposure to some prebiotics could modify it with positive or negative effects.     

Development of Wide-Spectrum Hybrid Bacteriocins for Food Biopreservation

The food industry demands new procedures and methods to produce minimally processed, ready to eat food with intact nutritional, taste, and flavor properties. The biopreservation and the use of both bacteriocins produced by lactic acid bacteria (LAB) and bacteriocinogenic strains as an alternative to substitute chemical antimicrobial for food preservation became increasingly important in the last two decades. When the new proposed natural preservatives techniques are applied, probiotics food can be obtained and, simultaneously, foodborne pathogens and spoilage contaminants can diminish. However, bacteriocins produced by LAB have a narrow antibacterial spectrum and are inactive against Gram-negative bacteria like Salmonella and the emergent enterohemorrhagic Escherichia coli. Knowing the mechanism of action and the structural features of microcins synthesized by Gram-negative bacteria and with potent antimicrobial activity against the mentioned microorganism, the proposal is to obtain hybrid peptides (microcin–bacteriocin) with broad antimicrobial spectrum. This review explains how the inability of bacteriocins to cross the outer membrane of Gram-negative bacteria unable them to act on the bacteria. It will also be discussed how a hybrid bacteriocin can be obtained.     

Anthocyanin composition in aged Chilean Cabernet Sauvignon red wines

Anthocyanins in aged Cabernet Sauvignon red wines were studied by HPLC–MS. The major anthocyanin in 6, 7, and 8 year old red wine extracts was the dimer vitisin A produced by condensation of malvidin-3-O-glucoside mediated by pyruvic acid. In aged wine, the content of malvidin-3-O-glucoside decreased with age with a concomitant increase of vitisin A. The latter is accompanied by several condensation products with molecular weight up to 1500 m/z. Differential pulse voltammetry indicated that aged wines have lower antioxidant capacity than young wine (400 mV), but higher than malvidin-3-O-glucoside (483 mV). Tafel’s plots showed that the electrochemical process occurring in aged wines is different from young wines. Six, seven and eight year old wines show similar behaviour with plots of 234, 177 and 188 mV/dec, respectively. These values are higher than the expected 120 mV/dec corresponding to a first electronic transfer but smaller compared to the 523 mV/dec corresponding to young wine.     

A Rapid and Eco-Friendly Method for Determination of Hydrolysable Tannins and Its Application to Honey Samples

This paper describes the development of a rapid and clean method for the determination of hydrolysable tannins in honey samples, focusing on an easy and green sample pretreatment and low generation of waste. The proposed method is based on the reaction between KIO₃ and hydrolysable tannin compounds in acetate buffer medium (pH 4.75), with formation of a colored product measured at 525 nm. The analytical conditions were optimized using experimental design (central composite design). The linear range obtained was 40.0–740 mg L^?1 (r?=?0.998), and the detection (LOD) and quantification (LOQ) limits were 12.2 and 40.8 mg L^?1, respectively. Acetate buffer was used to ensure formation of the colored product obtained by reaction between the chromogenic reagent and the analyte. The method showed good results when applied to honey samples, with recoveries in the range of 78.3–96.1 %, and the use of diffuse reflectance spectroscopy coupled with spot test analysis provided low reagent consumption and minimized waste generation. The results obtained with the proposed method were confirmed by a spectrophotometric method.     

Aromatization of heptanes,ethylcyclopentane, and cycloheptane over “nonacidic” platinum-alumina catalyst. Comparison of the mechanisms of aromatization over chromia-alumina and over platinum-alumina catalysts

n-Heptane, 2- and 3-methylhexane, ethylcyclopentane, and cycloheptane were passed in the presence of hydrogen at 500 °C over “nonacidic” platinum-alumina catalyst containing 3% by weight of platinum. The conversion ranged between 12 and 26%, depending on the interval of time the product was removed for analysis. In the case of cycloheptane, however, the conversion amounted to 98% during the first 30 min on stream and with time, during the approximate period between 2 and 3 h, it decreased to 69%. The products from the reaction contained besides toluene, also hydrocarbons resulting from a skeletal isomerization and dehydrocyclization of the original hydrocarbons, and to a smaller extent from a bond shift process, and a repetitive 1,5-ring closure followed by hydrogenolysis. Using 1,1-dimethylcyclohexane as a model compound, it was shown that the skeletal isomerization accompanying the aromatization of the seven-carbon hydrocarbons does not proceed through cationic intermediates. A survey of the literature relating to the mechanism of aromatization of hydrocarbon over “nonacidic” chromia-alumina and platinum-alumina catalysts is presented, and the differences between the two mechanisms are discussed.     

Aromatization of [1-14C]heptane over “nonacidic” platinum-alumina catalyst

[1-¹⁴C]Heptane was aromatized under 5 atm pressure over a “nonacidic” 3% platinum on alumina catalyst maintained at 500 °C. The reactant was pumped in at a HLSV of 0.88, and the hydrogen-to-heptane mole ratio was 5.1. The samples of product were collected (one during the first 90 min and another during the next 90 min), the toluene was separated from the respective samples, and the radioactivity in each position of the toluene was determined by a degradation sequence. The distribution of radioactivity in sample 1 was as follows: in position 1–2.6%, 2–38.6%; 3–14.5%; 4–4.2%, and in the methyl group—40.1%. Approximately similar distribution of radioactivity was found in sample 2. 1,6-Ring closure is the most important pathway leading to the formation of toluene from [1-¹⁴C]heptane; lesser amounts of repetitive, 1,5-ring closure and hydrogenolysis, and bond shift reactions followed by 1,6-ring closure and dehydration can explain the distribution of radioactivity. The participation of 1,7-ring closure in the reaction is also indicated.     

Biological effects and photodegradation by TiO(2) of terpenes present in industrial wastewater

The aim of this work was to study the biological effects of four monoterpenes, i.e. α-pinene, β-pinene, 3-carene and D-limonene present in the wastewater of a citrus transformation factory. The study was carried out by exposing V79 Chinese hamster cells to single terpene or to the mixture of four terpenes at concentrations corresponding to those in the wastewater evaluated by head space solid phase micro extraction and gas chromatography (HS-SPME-GC) analyses. Treatments with single or combined terpenes similarly affected cell vitality, but only the combined treatments induced the 6-thioguanine resistant mutants. Moreover the photocatalytic degradation of the four terpenes was successfully achieved with the photocatalyst TiO(2) Degussa P25 in both the actual effluent and in synthetic solutions.     

Self-organized TiO2 nanotube arrays: synthesis by anodization in an ionic liquid and assessment of photocatalytic properties

Self-organized TiO(2) nanotube (NT) arrays were produced by anodization in ethylene glycol (EG) electrolytes containing 1-n-butyl-3-methyl-imidazolium tetrafluoroborate (BMI.BF(4)) ionic liquid and water. The morphology of the as-formed NTs was considerably affected by changing the anodization time, voltage, and water and ionic liquid electrolyte concentrations. In general, a nanoporous layer was formed on the top surface of the TiO(2) NTs, except for anodization at 100 V with 1 vol % of BMI.BF(4), where the NT's mouth was revealed. The length and bottom diameter of the NTs as well as the pore diameter of the top layer showed a linear relationship with increased anodization voltage. These TiO(2) NTs were tested as photocatalysts for methyl orange photodegradation and hydrogen evolution from water/methanol solutions by UV light irradiation. The results show that the TiO(2) NTs obtained by anodization in EG/H(2)O/BMI.BF(4) electrolytes are active and efficient for both applications.     

Performance of near-infrared reflectance spectroscopy (NIRS) in routine analysis of C18 unsaturated fatty acids in intact rapeseed

This study was aimed to evaluate the performance of near-infrared reflectance spectroscopy (NIRS) in the analysis of the oil composition for fatty acids like oleic (C18:1), linoleic (C18:2) and linolenic (C18:3) in zero-erucic acid rapeseed (Brassica napus L.). Intact-seed samples of 1094 lines from a breeding programme for high-oleic acid rapeseed were analyzed by both NIRS and gas chromatography (GC). Previously developed calibration equations were initially used for NIRS analyses. The accuracy of NIRS was considerably improved by including some samples of the actual breeding population into the original calibration set and developing new calibration equations. The inclusion of twenty randomly selected samples led to a reduction of the standard error of performance (SEP) from 2.6% to 1.9% for oleic, from 3.8% to 2.0% for linoleic, and from 1.1% to 0.9% for linolenic acid. The application of the new equations to the remaining population of 1074 samples resulted in coefficients of correlation between NIRS and GC values of 0.95 for oleic, 0.92 for linoleic, and 0.90 for linolenic acid. Furthermore, the effectiveness of a selection for high oleic, high linoleic, or low linolenic acid content based on NIRS data was demonstrated. The results of this study will help potential users to choose the optimal selection strategy in routine analysis of C18 unsaturated fatty acids by NIRS within a breeding programme.