<abstract xml:lang="en"><title style='display:none'>Biosensors - classification, characterization and new trends</title>Biosensors represent promising analytical tools applicable in areas such as clinical diagnosis, food industry, environment monitoring and in other fields, where rapid and reliable analyses are needed. Some biosensors were successfully implemented in the commercial sphere, but majority needs to be improved in order to overcome some imperfections. This review covers the basic types, principles, constructions and use of biosensors as well as new trends used for their fabrication.</abstract>

Department of Nutrition and Food Assesment, Institute of Biochemistry, Nutrition and Health Protection, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinskeho 9, 812 37 Bratislava, Slovak Republic

Biorealis Ltd., Dubravska cesta 9, 841 04 Bratislava, Slovak Republic

Biosensors - classification, characterization and new trends

<abstract><title style='display:none'>Abstract</title> Three wild strains of <italic>Lactobacillus plantarum </italic>were investigated for their growth and ability to produce lactic acid, acetic acid and ethanol under aerobic and anaerobic conditions. They were tested at three different temperatures (30 °C, 37 °C and 45 °C). The growth of lactobacilli was studied by measuring optical density (OD) at λ = 600 nm and pH value at the following times. With increasing temperature difference of cell yield was observed. The final cell yield under aerobic conditions was higher. Organic acids and ethanol were analysed using an HPLC RID method. Formation of lactic acid (as the major metabolite) was the slowest during cultivation at 30 °C, but the final amount of lactic acid showed the highest values. Concentrations of metabolites produced by lactobacilli after 48th hours of cultivation were: 9.18-11.48 g.dm-3 (lactic acid), 0.84-1.65 g.dm-3 (acetic acid) and 2.51-4.03 g.dm-3 (ethanol). No significant differences (p = 0.05) were found in production of lactic acid and ethanol by different bacterial strains under aerobic and anaerobic conditions. Statistically significant differences (p = 0.05) were observed in production of acetic acid by 2L2 under aerobic and anaerobic conditions and for production of ethanol under anaerobic conditions by strains 1L5 and 2L2.</abstract>

Department of Food Technology, Institute of Biotechnology and Food Science, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, 812 37 Bratislava, Slovak Republic

Institute of Biotechnology and Food Science, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, 812 37 Bratislava, Slovak Republic

Influence of aerobic and anaerobic conditions on the growth and metabolism of selected strains of Lactobacillus plantarum

<abstract><title style='display:none'>Abstract</title>Zinc chloride is a commonly used activator in chemical activation of activated carbon. Various carbonaceous materials have been studied as potential source of activated carbon. The operating conditions are manipulated with attention to improve the properties and performance of activated carbon in the adsorption of water pollutants. However, the generalized attributes of zinc chloride activation in relation to the adsorptive performance of activated carbon are not well documented in much of published literature. Therefore, the present work is aimed to highlight the activation strategies and mechanisms of zinc chloride activation of activated carbon. The roles of impregnation ratio, period of activation and temperature are discussed to offer some insight into textural characteristics of activated carbon. The case studies on methylene blue adsorption are integrated to shed light on the external factors affecting the adsorption.</abstract>

Activated carbons by zinc chloride activation for dye removal – a commentary

<abstract><title style='display:none'>Abstract</title> Preparation of potassium nitrate from magnesium nitrate and potassium chloride was investigated. Prepared potassium nitrate contains less than 0.5 % chlorides and it can be applied as environmentally friendly fertilizer in hydroponic systems. After filtration out potassium nitrate crystals from the reciprocal system K+, Mg2+//Cl-, NO3- - H2O, the mother liquor still contains reasonable amount of potassium cations. By evaporation of the mother liquor, carnallite (MgCl2・KCl・6H2O) with admixture of MgCl2・6H2O crystallizes out. Decomposition of carnallite with cold water makes it possible to separate potassium chloride from this compound. When this KCl is returned back to the process of KNO3 making, utilization of potassium as high as 97 % can be achieved.</abstract>

Institute of Inorganic Chemistry, Technology and Materials, Faculty of Chemical and Food Technology STU in Bratislava, Radlinského 9, 812 37 Bratislava, Slovak Republic

VUCHT, a.s., Nobelova 34, 836 03 Bratislava, Slovak Republic

Preparation of potassium nitrate from potassium chloride and magnesium nitrate in a laboratory scale using industrial raw materials

<abstract><title style='display:none'>Abstract</title> The object of presented study was the evaluation of antioxidant activity of extract from Zingiber officinale. A method for the preparation of the extract was chosen, which enabled to isolate mostly phenolic compounds. According to the measurements with Folin-Ciocalteu reagent, obtained extract comprised total polyphenols (181.41 mgGAE/g of extract) from which flavonoids contributed to 7.8 % (14.15 mgquercetin/g of extract). Nuclear magnetic resonance (NMR) analysis showed that the phenolic ketones were predominant in the extracts of whole phenolic compounds. According to results of two spectrophotometric methods (ABTS and DPPH test), ginger extract showed stronger ability to scavenge DPPH radical than ABTS cation radical.</abstract>

Department of Nutrition and Food Assessment, Faculty of Chemical and Food Technology, Radlinského 9, 812 37 Bratislava, Slovakia

Department of NMR Spectroscopy and Mass Spectrometry, Faculty of Chemical and Food Technology, Radlinského 9, 812 37 Bratislava, Slovakia

Antioxidant activity of ginger extract and identification of its active components

<abstract><title style='display:none'>Abstract</title>The evaluation of antioxidant potential of food has received much attention in recent years. Antioxidant compounds can scavenge free radicals and thereby can protect the human body from free radicals. This study was focused on the isolation of curcuminoids from the dried turmeric rhizome, and studying their antioxidant activity. The presence of curcuminoids was identified in turmeric sample by Nuclear Magnetic Resonance (NMR) analysis. Since neutral curcumin is known to be poorly soluble, the synthesis of curcumin-cyclodextrin and curcumin-phospholipid complexes was also performed. The antioxidant activity of isolated curcuminoids was assessed by two methods (ABTS and FRAP assay) and their scavenging activities were compared with those of prepared complexes. The ability to reduce ABTS radical cation decreased as follows: quercetin &gt; trolox &gt; curcuminoids &gt; curcumin-cyclodextrin complex &gt; curcumin-phospholipid complex. The reducing potential of tested samples in descending order was quercetin &gt; trolox &gt; curcumin-cyclodextrin complex &gt; curcuminoids &gt; curcumin-phospholipid complex.</abstract>

Department of Nutrition and Food Assessment, Faculty of Chemical and Food Technology, Radlinského 9, 812 37 Bratislava,

Department of NMR Spectroscopy and Mass Spectrometry, Faculty of Chemical and Food Technology, Radlinského 9, 812 37 Bratislava,

Department of Biochemistry and Microbiology, Faculty of Chemical and Food Technology, Radlinského 9, 812 37 Bratislava,

Antioxidant properties of curcuminoids isolated from <italic>Curcuma longa</italic> L.

<abstract>
<title style='display:none'>Abstract</title>
Wheat varieties (IS Danubius and MS Luneta) bred in Slovakia were assessed for their bakery potential. It was found that flour produced from IS Danubius was characterised by significantly higher level of wet and dry gluten content (30.91 and 20.53 %, respectively) and exhibited higher gluten swelling capacity (29.3 %) in comparison to commercial wheat flour that is usually available in Slovak markets. Solvent retention capacity (solvation in specific solvents) of the tested flours was also determined. The measurements showed that these parameters significantly differ from those determined for commercially available flour, whereas the flour produced from IS Danubius wheat variety had the highest lactic acid retention capacity (124.15 %). Correlation analysis indicated strong positive correlations between solvent retention capacity values and gluten characteristics. Furthermore, it was found that baked rolls prepared from IS Danubius flour showed significantly higher loaf volume compared to commercial wheat flour. This study proves lactic acid retention capacity and sucrose retention capacity as parameters enabling the prediction of gluten network quality in dough and of qualitative parameters of baked goods. From the sensory evaluation resulted that the highest score for overall acceptance was observed in IS Danubius baked rolls, which significantly differs from both MS Luneta and commercial wheat flour.
</abstract>

Solvent retention capacity as a useful tool for quality evaluation of flours produced from Slovak bred wheat varieties

<abstract>
<title style='display:none'>Abstract</title>
Reaction Gibbs free energies for electron abstraction from phenol and its 74 derivatives were calculated using the composite <italic>ab-initio</italic> approach (G4) in combination with the implicit solvation model. Resulting values were correlated with 38 oxidation potentials obtained from cyclic voltammetry measurements. Substitution effect and the role of substituents in <italic>ortho</italic>-, <italic>meta</italic>-, and <italic>para</italic>-position were also quantified by Hammett constants. The evaluated linear dependences can be used to reliably estimate electrochemical potentials of substituted phenols solvated in water.
</abstract>

Substitution effect of phenol derivatives on electrochemical oxidation potentials: Correlation of theoretical reaction Gibbs free energies

<abstract>
<title style='display:none'>Abstract</title>
Atomic partial charges cannot be physically measured but they play a significant role in many chemical theories and theoretical models. Therefore, they are, evaluated from experimentally acquired properties or calculated by quantum chemistry computational methods. This study is focused on determining chemical accuracy of various theoretical methods of computing atomic partial charges based on quantum chemistry. Values of gas-phase atomic partial charges were acquired by Mulliken (MUL) population analysis, natural bond analysis (NBO), Merz-Singh-Kollman (MSK) scheme, and atomic polar tensor (APT) charges computed considering Density Functional Theory and <italic>ab initio</italic> Møller-Plesset up to the second order levels. Correlations between the calculated values were determined by principal component analysis (PCA) and further confirmed by linear regression. The best agreement between experimentally evaluated atomic partial charges and theoretical values was obtained with the MSK scheme.
</abstract>

Atomic partial charge model in chemistry: chemical accuracy of theoretical approaches for diatomic molecules

<abstract>
<title style='display:none'>Abstract</title>
Two potent novel perfluorophenylhydrazone derivatives are presented as multi-target compounds to combat Alzheimer disease C11H4BrF5N2S, 1-((4-bromothiophen-2-yl)methylene)-2-(perfluorophenyl) hydrazine, (I) and C12H6BrF5N2S, 1-((4-bromo-5-methylthiophen-2-yl)methylene)-2-(perfluorophenyl) hydrazine, (II), which can potentially be improved by further design. Their multi-target structures and features have been combined as potential AD therapeutics. Crystals (I), and (II), are molecules with two rings and a hydrazone part as a centre of the molecule. The compounds have been synthesised and characterised by elemental spectroscopic (1H-NMR) analysis. Crystal structures of the solid phase were determined by single crystal X-ray diffraction method. Both compounds crystallise in the monoclinic space group with <italic>Z</italic> = 4 and <italic>Z</italic> = 2 molecules per unit-cell. Compound (I) crystallises as a racemate in the centrosymmetric space group and compound (II) crystallises as a non-racemate in the non-centrosymmetric space group. Their “absolute configuration and conformation for bond values” were derived from the anomalous dispersion (rmad) for (II). Crystal structures revealed diverse non-covalent interactions such as intra- and inter-hydrogen bonding, π-ring…<italic>π</italic>-ring, C—H…<italic>π</italic>-ring. The expected stereochemistry of hydrazones atoms C7, N2 and N1 were confirmed for (I) and (II). Both molecules show “boat conformation” like a 6-membered ring. Results of single crystal studies were reproduced with the help of Hirshfeld surface study and Gaussian software.
</abstract>

Two novel potent perfluorophenylhydrazone derivatives, 1-((4-bromothiophen-2-yl)methylene)-2-(perfluorophenyl) hydrazine, and 1-((4-bromo-5-methylthiophen-2-yl)methylene)-2-(perfluorophenyl)hydrazine as multi-target compounds to combat Alzheimer disease and their crystal, molecular, and electronic properties

<abstract>
<title style='display:none'>Abstract</title>
Milk and dairy products are the most consumed foods in human diet and their safety is in the attention centre of control authorities. Aflatoxin M1 (AFM1) is a dangerous toxin that can occur in milk and dairy products as a metabolite formed from aflatoxin B1 contained in contaminated animal feed. Therefore, the aim of this study was to develop and validate a reliable method for the determination of AFM1 content in milk and dairy products based on HPLC with fluorescence detection employing immunoaffinity columns (IAC) pre-treatment. Optimal chromatographic separation of AFM1 was achieved using a water/acetonitrile mixture (80/20, v/v) as a mobile phase, column with C18 stationary phase maintained at 25 °C, and fluorescence detection at excitation wavelengths of 360 nm and emission of 440 nm. Efficacy of AFM1 extraction from the samples was found to be influenced by the elution agent composition. The best results were obtained using 1.25 mL of acetonitrile/methanol (3/2, v/v) and 1.25 mL of water. Validation parameters of the proposed method met the criteria set by the European legislation with the limits of detection and quantification at 0.002 and 0.007 µg/kg, respectively. Also, suitability of the method was confirmed by its application for AFM1 determination in certified reference material. Finally, the method was applied for AFM1 determination in 25 milk and dairy products collected in Slovakia; the AFM1 content was below the limit of quantification. It was concluded that the method is suitable for AFM1 content monitoring in milk and dairy products.
</abstract>

Development and validation of HPLC-FLD method for aflatoxin M1 determination in milk and dairy products

<abstract>
<title style='display:none'>Abstract</title>
Human gut microbiota has been in the centre of scientific interest for a long period of time. Overall health status of an individual has a great impact on the composition of gut microbiota; however, gut microbiota can affect human health. Antibiotic resistance genes (ARGs) are often a part of human gut microbiome. In this paper, total genomic DNA was extracted from stool samples of 147 healthy individuals and of 45 patients with severe alcoholic hepatitis. The presence of six common ARGs (<italic>bla</italic>TEM, <italic>bla</italic>SHV, <italic>bla</italic>OXA, <italic>vanA, tet</italic>(A), <italic>tet</italic>(E)) was analysed in the genomic DNA by end-point PCR. The results show significantly higher occurrence of ARGs in the DNA samples from patients (<italic>p</italic> = 0.0001) showing multiple ARGs significantly more often than in healthy individuals (<italic>p</italic> = 0.00003). Antibiotic treatment in patients strongly correlated with the occurrence of ARGs (<italic>p</italic> = 0.0038). Nutrition and sex of healthy individuals did not have significant effect on the occurrence of ARGs (<italic>p</italic> = 0.156; <italic>p</italic> = 0.456). ARGs’ occurrence in healthy individuals was the highest in the oldest age group, but the age of individuals and ARGs’ occurrence were not related (<italic>p</italic> = 0.617). In conclusion, the results underline the importance of health for normal functioning of gut microbiota. Antibiotic resistance represents a challenge in the treatment of patients with liver diseases.
</abstract>

Comparison of gut resistomes in healthy individuals and patients with severe alcoholic hepatitis

<abstract><title style='display:none'>Abstract</title>Two different absorption correction methods were compared in order to find out which method is preferable to improve solving and refining a crystal structure. Experiments were performed on the crystal of a tetrakis(μ2-acetato)-diaqua-di-copper(II) complex. The first correction method used was the numerical absorption correction with the aid of a crystal-shape model, and the other was the semi-empirical one, applying scaling routines to the intensity data.</abstract>

Faculty of Chemical and Food Technology, Slovak Technical University, Radlinského 9, SK-812 37, Bratislava,

STOE & Cie GmbH, Hilpertstrasse 10, D-64295, Darmstadt,

Comparison of different absorption corrections on the model structure of tetrakis(μ2-acetato)-diaqua-di-copper(II)

<abstract><title style='display:none'>Abstract</title>Arsenic (As) is metalloid, naturally present in the environment but also introduced by human activities. It is toxic and carcinogenic and its exposure to low or high concentrations can be fatal to human health. Arsenic contamination in drinking water threatens more than 150 million peoples all over the world. Therefore, treatment of As contaminated water is of unquestionable importance. The present review begins with an overview of As chemistry, distribution and toxicity, which are relevant aspects to understand and develop remediation techniques. The most common As removal processes (chemical precipitation, adsorption, ion exchange, membrane filtration, phytoremediation and electrocoagulation) are presented with discussion of their advantages, drawbacks and the main recent achievements.</abstract>

An overview of main arsenic removal technologies

<abstract xml:lang="en"><title style='display:none'>Lipophilization of flavonoids for their food, therapeutic and cosmetic applications</title>Flavonoids represent large group of plant pigments. These polyphenolic compounds may be found in the nature as active components of fruits, vegetables and other plants and derived products. Due to established biological effects they are attractive substances for many areas of human life. Many flavonoids are nowadays used in pharmaceutical, cosmetic and food preparations. Their practical applications are in most cases limited by low solubility and stability in lipophilic media. Chemical or enzymatic lipophilization of flavonoid skeleton may not only increase their solubility and stability in lipophilic environment but also their biological properties. This review summarizes current knowledge in this field.</abstract>

Institute of Biochemistry, Nutrition and Health Protection, Faculty of Chemical and Food Technology, Slovak University of Technology, SK-812 37 Bratislava

Institute of Experimental Pharmacology and Toxicology, Department of Biochemical Pharmacology, Slovak Academy of Sciences, SK-841 04 Bratislava

Department of Biotechnology, Faculty of Natural Sciences, University Ss. Cyril and Metodius, SK-917 01 Trnava

Lipophilization of flavonoids for their food, therapeutic and cosmetic applications

<abstract><title style='display:none'>Abstract</title> Heterogeneous TiO2/Cu2O nanocomposite was synthesized for photocatalysis through surface impregnation in conjunction with the environmentally friendly soft chemical reduction strategy. The detailed structural, compositional, optical and photoelectrochemical properties of the obtained products are analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), photoluminescence spectra (PL) and electron spin resonance (ESR) spectroscopy techniques. Moreover, methyl orange (MO) dye was chosen as the probe molecule for evaluation of the photocatalytic activities of the samples under visible light (λ &gt; 420 nm) irradiation. The experiments demonstrated that MO in aqueous solution was more efficiently photodegraded using TiO2/Cu2O composite photocatalysts than pure Cu2O alone. This was attributed to the good crystallinity, wide visible-light absorption range, and the efficient electron-hole pair separation properties of the TiO2/Cu2O nanoheterostructures. In this photocatalyst, visiblelight- active Cu2O component was used as a medium to absorb photons and convert them into photogenerated charges, and TiO2 nanoparticles were used as charge collectors to transport the photoinduced charges. The TiO2/Cu2O hybrid material showed improved separation of photoinduced electron-hole pairs owing to the potential-energy differences between Cu2O and TiO2, and therefore exhibited enhanced photocatalytic activity.</abstract>

Synergetic effects of Cu2O photocatalyst with titania and enhanced photoactivity under visible irradiation

Acta Chimica Slovaca

The Journal of Slovak University of Technology in Bratislava

Acta Chimica Slovaca publish papers on fundamental and applied aspects of chemistry, biochemistry, chemical technology, chemical engineering and process control, biotechnology and food...

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Acta Chimica Slovaca publish papers on fundamental and applied aspects of chemistry, biochemistry, chemical technology, chemical engineering and...