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Volume 13 (2020): Issue 1 (April 2020)

Volume 12 (2019): Issue 2 (October 2019)

Volume 12 (2019): Issue 1 (April 2019)

Volume 11 (2018): Issue 2 (October 2018)

Volume 11 (2018): Issue 1 (April 2018)

Volume 10 (2017): Issue 2 (December 2017)

Volume 10 (2017): Issue 1 (April 2017)

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Volume 9 (2016): Issue 1 (April 2016)

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Volume 8 (2015): Issue 1 (April 2015)

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Volume 6 (2013): Issue 1 (April 2013)

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Volume 5 (2012): Issue 1 (April 2012)

Journal Details
Format
Journal
eISSN
1339-3065
First Published
10 Dec 2012
Publication timeframe
2 times per year
Languages
English

Search

Volume 12 (2019): Issue 2 (October 2019)

Journal Details
Format
Journal
eISSN
1339-3065
First Published
10 Dec 2012
Publication timeframe
2 times per year
Languages
English

Search

11 Articles
access type Open Access

Slovak natural zeolites as a suitable medium for antibiotics elimination from wastewater

Published Online: 21 Jan 2020
Page range: 163 - 167

Abstract

Abstract

Pharmaceuticals are one of the most used compounds present in various environmental compartments. Due to their high consumption and possible unhealthy effect on ecosystems, pharmaceuticals have been identified as “emerging organic contaminants”. Since these compounds have medium to high polarity, they end up in the water compartment after being used. This work deals with the sorption of three pharmaceutical substances from the therapeutic group of antibiotics. Specifically we have focused on Azithromycin, Clarithromycin and Erythromycin. Three fractions of the natural Slovak zeolites (200 μm, 0.5—1 mm and 1.5—2 mm) were used as the sorption medium. Experimental results have proven very effective sorption of antibiotics by zeolites. Azithromycin removal of over 99 % for all three zeolite fractions from wastewater treatment plant Stupava and wastewater treatment plant Devínska Nová Ves was achieved. Clarithromycin removal of 79 % for fraction 1—2.5 mm, 87.3 % for fraction 0.5—1 mm and of 99.8 % for fraction 200 μm from the effluent of wastewater treatment plant Stupava was observed. Erythromycin removal of 31.3 % for fraction 1—2.5 mm, 66.9 % for fraction 0.5—1mm and of 94.7 % for fraction 200 μm from effluent of wastewater treatment plant Stupava was measured. More than 95 % of Clarithromycin and Erythromycin were eliminated from the effluent of wastewater treatment plant Devínska Nová Ves. The highest elimination percentage was observed for the smallest zeolite fraction due to the highest specific surface area.

Keywords

  • antibiotics
  • pharmaceuticals
  • wastewater
  • zeolites
access type Open Access

Quantum-chemical studies of rutile nanoparticles toxicity I. Defect-free rod-like model clusters

Published Online: 21 Jan 2020
Page range: 168 - 174

Abstract

Abstract

Using the semiempirical PM6 method, structures of a rod-like [Ti40O124H81]7– model cluster and of [Ti40O124H81Cu]5– with Cu2+ coordinated at various sites were optimized in order to assess the toxicity of rutile nanoparticles. If the relative toxicity of individual Ti centers in rod-like rutile nanoparticles can be evaluated by the electron density transfer to a Cu2+ probe, its maximal values can be ascribed to the pentacoordinated corner and hexacoordinated edge Ti centers with three Ti—OH bonds. However, these centers exhibit the least negative interaction energies which can be compensated by the significantly better accessibility of the corner Ti center compared with that of the remaining ones. Ti centers with the most negative interaction energy parameters exhibit the lowest extent of electron density transfer to a Cu2+ probe. Rutile nanoparticles destruction starts at pentacoordinated Ti face centers.

Keywords

  • protonated rutile nanoparticle
  • PM6 semiempirical method
  • Cu(II) probe
  • electron density transfer
  • active centers
access type Open Access

Growth of Staphylococcus aureus 2064 described by predictive microbiology: From primary to secondary models

Published Online: 21 Jan 2020
Page range: 175 - 181

Abstract

Abstract

The growth of Staphylococcus aureus 2064 isolate in model nutrient broth was studied as affected by temperature and water activity using principles and models of predictive microbiology. Specific rates resulting from growth curves fitted by the Baranyi model were modelled by the secondary Ratkowsky model for suboptimal temperature range (RTKsub) as well as the Ratkowsky extended model (RTKext) and cardinal model (CM) in the whole temperature range. With the biological background of the RTKext model, cardinal values of temperature Tmin = 6.06 °C and Tmax = 47.9 °C and water activity aw min = 0.859 were calculated and validated with cardinal values estimated by CM (Tmin = 7.72 °C, Tmax = 46.73 °C, aw min = 0.808). CM also provided other cardinal values, Topt = 40.63 °C, awopt = 0.994, as well as optimal specific growth rate of 1.97 h–1 (at Topt and awopt). To evaluate the goodness of fit of all models, mathematical and graphical validation was performed and the statistical indices proved appropriateness of all the secondary models used.

Keywords

  • food safety
  • prediction
  • temperature
  • water activity
access type Open Access

3-Hydroxymethyl-1,4-dihydro-4-oxoquinoline like compound with promising biological and complexing activity

Published Online: 21 Jan 2020
Page range: 182 - 184

Abstract

access type Open Access

Steam explosion of wood particles from fibreboard and particle board with indirect control by enzymatic hydrolysis

Published Online: 21 Jan 2020
Page range: 185 - 191

Abstract

Abstract

Pretreatment of particles obtained from lignocellulosic materials by steam explosion with indirect control by enzymatic hydrolysis has been studied. The dendromass pretreatment model has been applied for recycled fibreboard and particle board based on softwood. Their structure and chemical composition partly predetermine these lignocellulosic materials consisting of a mixture of spruce and fir particles also for bioethanol production. Optimum steam explosion temperature of 205 °C was determined based on the concentration of total monosaccharides — glucose, xylose and arabinose, among all experimentally prepared hydrolysates. This corresponds to basic conditions for fine disintegration of biomass to lignocellulosic structure with good holocellulose accessibility. Particles obtained from fibreboard and particle board primarily consisting of softwood without steam explosion pretreatment provide relatively low cellulose accessibility for commercial enzymes activity while monosaccharides concentration is partly reduced because of torrefaction at high temperatures. The concentration of monosaccharides in hydrolysates was determined for original sample and each steam explosion temperature. Based on the steam explosion conditions, the effect of severity factors was investigated to find optimum pretreatment conditions to increase accessibility of softwood cellulose and hemicelluloses. The identified optimum severity factor RO = 4.09 matches the optimum steam explosion temperature of 205 °C and the residence time of 10 minutes.

Keywords

  • biofuel industry
  • dendromass
  • fibreboard
  • particle board
  • severity factor
  • steam explosion
access type Open Access

Application of milk thistle (Silybum marianum) in functional biscuits formulation

Published Online: 21 Jan 2020
Page range: 192 - 199

Abstract

Abstract

Due to the substantial protective effects of milk thistle to liver against various chemical compounds, a new healthy cereal product replacing wheat flour with milk thistle seed flour in the range of 5; 10; 15; 20; 25 and 30 % has been studied. As it has been found, milk thistle seed flour is a good source of total dietary fibre, proteins, mineral compounds and fats. During the experiments, effects of wheat flour replacement on technological properties of the dough were studied using Mixolab characteristics. From the results it can be stated that milk thistle seed flour replacement led to a decrease in water absorption and stability of dough. After baking, physical, mechanical, colour and sensorial properties of the biscuits were studied. The results have shown that even a 10 % replacement results in a significant difference at p < 0.05 in measured parameters compared to ones. However, it has been calculated that statistically insignificant replacement of wheat flour with milk thistle seed flour is up to 9.3 % with quality and sensorial parameters of the biscuits equal to those prepared from 100 % wheat flour. Thus, production of functional biscuits at these conditions is fully possible.

Keywords

  • biscuits
  • functional foods
  • milk thistle
  • Mixolab
  • sensory analysis
  • silymarin
  • texture
access type Open Access

Selectedin vitro methods to determine antioxidant activity of hydrophilic/lipophilic substances

Published Online: 21 Jan 2020
Page range: 200 - 211

Abstract

Abstract

The topic of free radicals and related antioxidants is greatly discussed nowadays. Antioxidants help to neutralize free radicals before damaging cells. In the absence of antioxidants, a phenomenon called oxidative stress occurs. Oxidative stress can cause many diseases e.g. Alzheimer’s disease and cardiovascular diseases. Therefore, antioxidant activity of various compounds and the mechanism of their action have to be studied. Antioxidant activity and capacity are measured by in vitro and in vivo methods; in vitro methods are divided into two groups according to chemical reactions between free radicals and antioxidants. The first group is based on the transfer of hydrogen atoms (HAT), the second one on the transfer of electrons (ET). The most frequently used methods in the field of antioxidant power measurement are discussed in this work in terms of their principle, mechanism, methodology, the way of results evaluation and possible pitfalls.

Keywords

  • ET methods
  • HAT methods
  • oxidative stress
  • total antioxidant activity
access type Open Access

Antioxidant action of phenols: Revisiting theoretical calculations of their thermodynamics

Published Online: 21 Jan 2020
Page range: 212 - 217

Abstract

Abstract

Theoretical prediction ability of M06-2X functional was tested for thermodynamics of phenol, 15 para and 15 meta phenol derivatives. Calculations were done for gas phase as well as for polar and nonpolar solvents. Although predicted values might be shifted from the experimental ones in the framework of the employed DFT functional and basis set, the calculated and experimental data sets correlate well together. Very good linearity was found especially for the correlation of experimental and theoretical proton affinities. Hammett type correlations between the environments considered were compared. The phenolic C—O bond length was also tested as an alternative substituent effect descriptor while the type and position of the functional group on the aromatic ring have a direct effect on the phenolic bond.

Keywords

  • DFT
  • Hammett constants
  • M06-2X functional
  • reaction enthalpy
access type Open Access

Neural network based explicit MPC for chemical reactor control

Published Online: 21 Jan 2020
Page range: 218 - 223

Abstract

Abstract

In this paper, implementation of deep neural networks applied in process control is presented. In our approach, training of the neural network is based on model predictive control, which is popular for its ability to be tuned by the weighting matrices and for it respecting the system constraints. A neural network that can approximate the MPC behavior by mimicking the control input trajectory while the constraints on states and control input remain unimpaired by the weighting matrices is introduced. This approach is demonstrated in a simulation case study involving a continuous stirred tank reactor where a multi-component chemical reaction takes place.

Keywords

  • model predictive control
  • artificial neural networks
  • process control
  • continuous stirred tank reactor
access type Open Access

Corrigendum to: Thermal inactivation kinetics of Aspergillus oryzae β-galactosidase in concentrated lactose solution

Published Online: 21 Jan 2020
Page range: 224 - 224

Abstract

access type Open Access

DFT and ab initio calculations of ionization potentials, proton affinities and bond dissociation enthalpies of aromatic compounds

Published Online: 21 Jan 2020
Page range: 225 - 240

Abstract

Abstract

Theoretical study of phenol, thiophenol, benzeneselenol, aniline and their para-amino and paranitro derivatives is presented. Neutral molecules, their deprotonated forms, neutral radicals, and radical cations were studied using three Density Functional Theory (DFT) functionals as well as combined DFT and ab initio G4 method in order to calculate the N—H, O—H, S—H, and Se—H bond dissociation enthalpies (BDE), proton affinities of corresponding anions (PA) and ionization potentials (IP) of studied compounds. These quantities represent fundamental reaction enthalpies related to the radical scavenging action of primary antioxidants. Calculated values were compared with available experimental data to assess applicability of the computational approaches employed. M06-2X/6-311++G(d,p) and G4 methods showed the best agreement with the available experimental gas-phase reaction enthalpies.

Keywords

  • Antioxidant
  • radical
  • anion
  • electron-donating group
  • electron-withdrawing group
11 Articles
access type Open Access

Slovak natural zeolites as a suitable medium for antibiotics elimination from wastewater

Published Online: 21 Jan 2020
Page range: 163 - 167

Abstract

Abstract

Pharmaceuticals are one of the most used compounds present in various environmental compartments. Due to their high consumption and possible unhealthy effect on ecosystems, pharmaceuticals have been identified as “emerging organic contaminants”. Since these compounds have medium to high polarity, they end up in the water compartment after being used. This work deals with the sorption of three pharmaceutical substances from the therapeutic group of antibiotics. Specifically we have focused on Azithromycin, Clarithromycin and Erythromycin. Three fractions of the natural Slovak zeolites (200 μm, 0.5—1 mm and 1.5—2 mm) were used as the sorption medium. Experimental results have proven very effective sorption of antibiotics by zeolites. Azithromycin removal of over 99 % for all three zeolite fractions from wastewater treatment plant Stupava and wastewater treatment plant Devínska Nová Ves was achieved. Clarithromycin removal of 79 % for fraction 1—2.5 mm, 87.3 % for fraction 0.5—1 mm and of 99.8 % for fraction 200 μm from the effluent of wastewater treatment plant Stupava was observed. Erythromycin removal of 31.3 % for fraction 1—2.5 mm, 66.9 % for fraction 0.5—1mm and of 94.7 % for fraction 200 μm from effluent of wastewater treatment plant Stupava was measured. More than 95 % of Clarithromycin and Erythromycin were eliminated from the effluent of wastewater treatment plant Devínska Nová Ves. The highest elimination percentage was observed for the smallest zeolite fraction due to the highest specific surface area.

Keywords

  • antibiotics
  • pharmaceuticals
  • wastewater
  • zeolites
access type Open Access

Quantum-chemical studies of rutile nanoparticles toxicity I. Defect-free rod-like model clusters

Published Online: 21 Jan 2020
Page range: 168 - 174

Abstract

Abstract

Using the semiempirical PM6 method, structures of a rod-like [Ti40O124H81]7– model cluster and of [Ti40O124H81Cu]5– with Cu2+ coordinated at various sites were optimized in order to assess the toxicity of rutile nanoparticles. If the relative toxicity of individual Ti centers in rod-like rutile nanoparticles can be evaluated by the electron density transfer to a Cu2+ probe, its maximal values can be ascribed to the pentacoordinated corner and hexacoordinated edge Ti centers with three Ti—OH bonds. However, these centers exhibit the least negative interaction energies which can be compensated by the significantly better accessibility of the corner Ti center compared with that of the remaining ones. Ti centers with the most negative interaction energy parameters exhibit the lowest extent of electron density transfer to a Cu2+ probe. Rutile nanoparticles destruction starts at pentacoordinated Ti face centers.

Keywords

  • protonated rutile nanoparticle
  • PM6 semiempirical method
  • Cu(II) probe
  • electron density transfer
  • active centers
access type Open Access

Growth of Staphylococcus aureus 2064 described by predictive microbiology: From primary to secondary models

Published Online: 21 Jan 2020
Page range: 175 - 181

Abstract

Abstract

The growth of Staphylococcus aureus 2064 isolate in model nutrient broth was studied as affected by temperature and water activity using principles and models of predictive microbiology. Specific rates resulting from growth curves fitted by the Baranyi model were modelled by the secondary Ratkowsky model for suboptimal temperature range (RTKsub) as well as the Ratkowsky extended model (RTKext) and cardinal model (CM) in the whole temperature range. With the biological background of the RTKext model, cardinal values of temperature Tmin = 6.06 °C and Tmax = 47.9 °C and water activity aw min = 0.859 were calculated and validated with cardinal values estimated by CM (Tmin = 7.72 °C, Tmax = 46.73 °C, aw min = 0.808). CM also provided other cardinal values, Topt = 40.63 °C, awopt = 0.994, as well as optimal specific growth rate of 1.97 h–1 (at Topt and awopt). To evaluate the goodness of fit of all models, mathematical and graphical validation was performed and the statistical indices proved appropriateness of all the secondary models used.

Keywords

  • food safety
  • prediction
  • temperature
  • water activity
access type Open Access

3-Hydroxymethyl-1,4-dihydro-4-oxoquinoline like compound with promising biological and complexing activity

Published Online: 21 Jan 2020
Page range: 182 - 184

Abstract

access type Open Access

Steam explosion of wood particles from fibreboard and particle board with indirect control by enzymatic hydrolysis

Published Online: 21 Jan 2020
Page range: 185 - 191

Abstract

Abstract

Pretreatment of particles obtained from lignocellulosic materials by steam explosion with indirect control by enzymatic hydrolysis has been studied. The dendromass pretreatment model has been applied for recycled fibreboard and particle board based on softwood. Their structure and chemical composition partly predetermine these lignocellulosic materials consisting of a mixture of spruce and fir particles also for bioethanol production. Optimum steam explosion temperature of 205 °C was determined based on the concentration of total monosaccharides — glucose, xylose and arabinose, among all experimentally prepared hydrolysates. This corresponds to basic conditions for fine disintegration of biomass to lignocellulosic structure with good holocellulose accessibility. Particles obtained from fibreboard and particle board primarily consisting of softwood without steam explosion pretreatment provide relatively low cellulose accessibility for commercial enzymes activity while monosaccharides concentration is partly reduced because of torrefaction at high temperatures. The concentration of monosaccharides in hydrolysates was determined for original sample and each steam explosion temperature. Based on the steam explosion conditions, the effect of severity factors was investigated to find optimum pretreatment conditions to increase accessibility of softwood cellulose and hemicelluloses. The identified optimum severity factor RO = 4.09 matches the optimum steam explosion temperature of 205 °C and the residence time of 10 minutes.

Keywords

  • biofuel industry
  • dendromass
  • fibreboard
  • particle board
  • severity factor
  • steam explosion
access type Open Access

Application of milk thistle (Silybum marianum) in functional biscuits formulation

Published Online: 21 Jan 2020
Page range: 192 - 199

Abstract

Abstract

Due to the substantial protective effects of milk thistle to liver against various chemical compounds, a new healthy cereal product replacing wheat flour with milk thistle seed flour in the range of 5; 10; 15; 20; 25 and 30 % has been studied. As it has been found, milk thistle seed flour is a good source of total dietary fibre, proteins, mineral compounds and fats. During the experiments, effects of wheat flour replacement on technological properties of the dough were studied using Mixolab characteristics. From the results it can be stated that milk thistle seed flour replacement led to a decrease in water absorption and stability of dough. After baking, physical, mechanical, colour and sensorial properties of the biscuits were studied. The results have shown that even a 10 % replacement results in a significant difference at p < 0.05 in measured parameters compared to ones. However, it has been calculated that statistically insignificant replacement of wheat flour with milk thistle seed flour is up to 9.3 % with quality and sensorial parameters of the biscuits equal to those prepared from 100 % wheat flour. Thus, production of functional biscuits at these conditions is fully possible.

Keywords

  • biscuits
  • functional foods
  • milk thistle
  • Mixolab
  • sensory analysis
  • silymarin
  • texture
access type Open Access

Selectedin vitro methods to determine antioxidant activity of hydrophilic/lipophilic substances

Published Online: 21 Jan 2020
Page range: 200 - 211

Abstract

Abstract

The topic of free radicals and related antioxidants is greatly discussed nowadays. Antioxidants help to neutralize free radicals before damaging cells. In the absence of antioxidants, a phenomenon called oxidative stress occurs. Oxidative stress can cause many diseases e.g. Alzheimer’s disease and cardiovascular diseases. Therefore, antioxidant activity of various compounds and the mechanism of their action have to be studied. Antioxidant activity and capacity are measured by in vitro and in vivo methods; in vitro methods are divided into two groups according to chemical reactions between free radicals and antioxidants. The first group is based on the transfer of hydrogen atoms (HAT), the second one on the transfer of electrons (ET). The most frequently used methods in the field of antioxidant power measurement are discussed in this work in terms of their principle, mechanism, methodology, the way of results evaluation and possible pitfalls.

Keywords

  • ET methods
  • HAT methods
  • oxidative stress
  • total antioxidant activity
access type Open Access

Antioxidant action of phenols: Revisiting theoretical calculations of their thermodynamics

Published Online: 21 Jan 2020
Page range: 212 - 217

Abstract

Abstract

Theoretical prediction ability of M06-2X functional was tested for thermodynamics of phenol, 15 para and 15 meta phenol derivatives. Calculations were done for gas phase as well as for polar and nonpolar solvents. Although predicted values might be shifted from the experimental ones in the framework of the employed DFT functional and basis set, the calculated and experimental data sets correlate well together. Very good linearity was found especially for the correlation of experimental and theoretical proton affinities. Hammett type correlations between the environments considered were compared. The phenolic C—O bond length was also tested as an alternative substituent effect descriptor while the type and position of the functional group on the aromatic ring have a direct effect on the phenolic bond.

Keywords

  • DFT
  • Hammett constants
  • M06-2X functional
  • reaction enthalpy
access type Open Access

Neural network based explicit MPC for chemical reactor control

Published Online: 21 Jan 2020
Page range: 218 - 223

Abstract

Abstract

In this paper, implementation of deep neural networks applied in process control is presented. In our approach, training of the neural network is based on model predictive control, which is popular for its ability to be tuned by the weighting matrices and for it respecting the system constraints. A neural network that can approximate the MPC behavior by mimicking the control input trajectory while the constraints on states and control input remain unimpaired by the weighting matrices is introduced. This approach is demonstrated in a simulation case study involving a continuous stirred tank reactor where a multi-component chemical reaction takes place.

Keywords

  • model predictive control
  • artificial neural networks
  • process control
  • continuous stirred tank reactor
access type Open Access

Corrigendum to: Thermal inactivation kinetics of Aspergillus oryzae β-galactosidase in concentrated lactose solution

Published Online: 21 Jan 2020
Page range: 224 - 224

Abstract

access type Open Access

DFT and ab initio calculations of ionization potentials, proton affinities and bond dissociation enthalpies of aromatic compounds

Published Online: 21 Jan 2020
Page range: 225 - 240

Abstract

Abstract

Theoretical study of phenol, thiophenol, benzeneselenol, aniline and their para-amino and paranitro derivatives is presented. Neutral molecules, their deprotonated forms, neutral radicals, and radical cations were studied using three Density Functional Theory (DFT) functionals as well as combined DFT and ab initio G4 method in order to calculate the N—H, O—H, S—H, and Se—H bond dissociation enthalpies (BDE), proton affinities of corresponding anions (PA) and ionization potentials (IP) of studied compounds. These quantities represent fundamental reaction enthalpies related to the radical scavenging action of primary antioxidants. Calculated values were compared with available experimental data to assess applicability of the computational approaches employed. M06-2X/6-311++G(d,p) and G4 methods showed the best agreement with the available experimental gas-phase reaction enthalpies.

Keywords

  • Antioxidant
  • radical
  • anion
  • electron-donating group
  • electron-withdrawing group

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