Papers by Tatjana Krivorotova
2 Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky Sq.... more 2 Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky Sq. 2, 162 06 Prague 6, Czech Republic Reversible addition-fragmentation chain transfer (RAFT) polymerization of lauryl methacrylate (LMA) in the presence of S-methoxycarbonyl phenylmethyl dithiobenzoate (MCPDB) as a RAFT chain transfer agent (CTA) and subsequent RAFT polymerization of poly(ethylene oxide) monomethyl ether methacrylate (PEO5MEMA or PEO45MEMA) was done with the aim to prepare amphiphilic diblock copolymer brushes of controlled structure. The molecular weight of PLMA and PLMA-b-PPEO5MEMA copolymers was evaluated by several methods including SEC calibrated using polystyrene standards, and end-group analysis by 1H NMR and UV-Vis. The kinetics of LMA polymerization was followed by 1H NMR spectroscopy by comparing the signals attributed to the monomer and corresponding monomeric units in PLMA. RAFT polymerization of LMA at the ratio [MCPDP] : [AIBN] = 4 demonstrated the “living” ...
Journal of Biotechnology, 2016
Eating disorders (EDs) like anorexia nervosa (AN) and bulimia nervosa (BN) are complex neuropsych... more Eating disorders (EDs) like anorexia nervosa (AN) and bulimia nervosa (BN) are complex neuropsychiatric conditions characterized by a multifactorial etiopathogenesis. The clinical diagnosis of EDs
New Biotechnology, 2018
S99 tumor targeting and accumulation of IONP were achieved by using the chitosan nanocarrier, thu... more S99 tumor targeting and accumulation of IONP were achieved by using the chitosan nanocarrier, thus, this could serve as an enhanced MRI contrast agent. On the other hand, the different loading contents of IONP clearly affected the accumulations in the tumor and the liver, thus the quality of MR imaging was also affected by the loading contents of IONP in the nanocarrier. A high loading content (40 wt.%) with rigid properties significantly reduced the accumulation and MR imaging signal in the tumor and increased the liver uptake.
New Biotechnology, 2018
S99 tumor targeting and accumulation of IONP were achieved by using the chitosan nanocarrier, thu... more S99 tumor targeting and accumulation of IONP were achieved by using the chitosan nanocarrier, thus, this could serve as an enhanced MRI contrast agent. On the other hand, the different loading contents of IONP clearly affected the accumulations in the tumor and the liver, thus the quality of MR imaging was also affected by the loading contents of IONP in the nanocarrier. A high loading content (40 wt.%) with rigid properties significantly reduced the accumulation and MR imaging signal in the tumor and increased the liver uptake.
Journal of Biotechnology, 2018
only be revealed through histopathological examination. Animal tissue and plant structures compli... more only be revealed through histopathological examination. Animal tissue and plant structures compliant with the recipe were also found. Histological examination reveals the morphological structure of the tissues and organs used in meat products. We consider the histopathological examination to be a simple and effective tool for assessing and highlighting structural nonconformity when the product meets the physicochemical and microbiological standards.
Agronomy, 2018
Jerusalem artichoke tubers have diverse applications in the food industry as well as in biotechno... more Jerusalem artichoke tubers have diverse applications in the food industry as well as in biotechnology. Their suitability depends mostly on the inulin content. Seasonal fluctuations of fructan exohydrolase activity responsible for inulin degradation was investigated in the tubers of three Jerusalem artichoke cultivars. The changes of fructan exohydrolase activity positively correlated with the changes of the content of total and short fructooligosaccharides. Therefore, to extract inulin with higher degree of polymerization for biotechnological purposes, the tubers of Jerusalem artichoke should be uprooted in autumn before the level of fructan exohydrolase reaches its maximum. If short fructooligosaccharides are desirable, the tubers in late autumn or spring tubers overwintered in soil are suitable.
Frontiers in Microbiology, 2018
Nisin is a recognized bacteriocin widely used in food processing, however, being ineffective agai... more Nisin is a recognized bacteriocin widely used in food processing, however, being ineffective against gram-negative bacteria and in complex food systems. As a result, the research of methods that have cell wall-permeabilizing activity is required. In this study, electroporation to trigger sensitization of gram-negative bacteria to nisin-loaded pectin nanoparticles was used. As a model microorganism, bioluminescent strain of E. coli was introduced. Inactivation kinetics using nanosecond pulsed electric fields (PEFs) and nisin nanoparticles have been studied in a broad range (100-900 ns, 10-30 kV/cm) of pulse parameters. As a reference, the microsecond range protocols (100 μs × 8) have been applied. It was determined that the 20-30 kV/cm electric field with pulse duration ranging from 500 to 900 ns was sufficient to cause significant permeabilization of E. coli to trigger a synergistic response with the nisin treatment. The kinetics of the inactivation was studied with a time resolution of 2.5 min, which provided experimental evidence that the efficacy of nisinbased treatment can be effectively controlled in time using PEF. The results and the proposed methodology for rapid detection of bacteria inactivation rate based on bioluminescence may be useful in the development and optimization of protocols for PEF-based treatments.
Frontiers in Microbiology, 2018
Nisin is a known bacteriocin, which exhibits a wide spectrum of antimicrobial activity, while com... more Nisin is a known bacteriocin, which exhibits a wide spectrum of antimicrobial activity, while commonly being inefficient against Gram-negative bacteria. In this work, we present a proof of concept of novel antimicrobial methodology using targeted magnetic nisin-loaded nano-carriers [iron oxide nanoparticles (NPs) (11-13 nm) capped with citric, ascorbic, and gallic acids], which are activated by high pulsed electric and electromagnetic fields allowing to overcome the nisin-resistance of bacteria. As a cell model the Gram-positive bacteria Bacillus subtilis and Gram-negative Escherichia coli were used. We have applied 10 and 30 kV cm −1 electric field pulses (100 µs × 8) separately and in combination with two pulsed magnetic field protocols: (1) high dB/dt 3.3 T × 50 and (2) 10 mT, 100 kHz, 2 min protocol to induce additional permeabilization and local magnetic hyperthermia. We have shown that the high dB/dt pulsed magnetic fields increase the antimicrobial efficiency of nisin NPs similar to electroporation or magnetic hyperthermia methods and a synergistic treatment is also possible. The results of our work are promising for the development of new methods for treatment of the drug-resistant foodborne pathogens to minimize the risks of invasive infections.
European Polymer Journal, 2017
and properties of amphiphilic pentablock copolymers with repeating blocks of poly(2-hydroxyethyl ... more and properties of amphiphilic pentablock copolymers with repeating blocks of poly(2-hydroxyethyl methacrylate) and poly(butyl methacrylate),
Czech Journal of Food Sciences, 2017
Rheological and textural properties of whole milk yogurt enriched with the flour from tubers of t... more Rheological and textural properties of whole milk yogurt enriched with the flour from tubers of two Jerusalem artichoke cultivars were investigated. They were compared with the properties of yogurts enriched with the extracts containing fructooligosaccharides and other carbohydrates isolated by different methods from tuber flour. Chemical analysis of extracts was also performed. All yogurts enriched with tuber flour or other carbohydrates exhibited viscoelastic behaviour.
Biotechnology Progress, 2016
The relationship between pectin structure and the antimicrobial activity of nisin‐loaded pectin p... more The relationship between pectin structure and the antimicrobial activity of nisin‐loaded pectin particles was examined. The antimicrobial activity of five different nisin‐loaded pectin particles, i.e., nisin‐loaded high methoxyl pectin, low methoxyl pectin, pectic acid, dodecyl pectin with 5.4 and 25% degree of substitution were tested in the pH range of 4.0–7.0 by agar‐diffusion assay and agar plate count methods. It was found that the degree of esterification of carboxyl group of galacturonic acid in pectin molecule is important for the antimicrobial activity of nisin‐loaded pectin particles. Nisin‐loaded particles prepared using pectic acid or the pectin with low degree of esterification exhibit higher antimicrobial activity than nisin‐loaded high methoxyl pectin particles. Pectins with free carboxyl groups or of low degree of esterification are the most suitable for particles preparation. Moreover, nisin‐loaded pectin particles were active at close to neutral or neutral pH values. Therefore, they could be effectively applied for food preservation. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 33:245–251, 2017
Innovative Food Science & Emerging Technologies, 2016
Pulsed electric fields (PEF) trigger the electroporation phenomenon in cell membranes, which has ... more Pulsed electric fields (PEF) trigger the electroporation phenomenon in cell membranes, which has found many biotechnological applications including food processing. Nisin is a prominent lantibiotic widely used as a food preservative due to its high potency against many bacteria; its efficacy depends on various environmental factors and nisin resistance is a common problem. In this work we have applied novel nisin-loaded pectin nanoparticles in combination with sub-microsecond and microsecond range electroporation for inactivation of nisin-resistant Escherichia coli. The 5-30 kVcm −1 square wave 1 kHz pulse bursts of 250 ns, 500 ns, and 100 μs were used. The PEF treatment combined with nisin nanoparticles further improved the inactivation efficacy (up to 3.7 log reduction) compared to separate procedures (up to 1.5 log reduction); this effect is scalable and does not depend on the cell concentration. Industrial relevance: We have designed experiments and provided data that has direct application in food preservation and processing. Nisin is a prominent lantibiotic that is widely used as a food preservative due to its high potency against many bacteria. Nevertheless, its efficacy depends on various environmental factors and the nisin resistance is a common problem. We have used the pectin encapsulation that allowed addressing the susceptibility of nisin to environmental factors such as pH or food composition, while the PEF technology enabled a non-thermal increase of the membrane permeabilization and overcoming the nisin-resistance of the bacteria. We have also shown that the only reason to use submicrosecond pulses instead of the microsecond ones for eradication of the bacteria is the possible minimization of energy costs for generation of PEF. If the total energy of the pulse burst is the same the inactivation efficacy is also identical.
LWT - Food Science and Technology, 2016
Food Hydrocolloids, 2016
Nisin is a small cationic peptide composed of 34 amino acid residues. It exhibits a wide spectrum... more Nisin is a small cationic peptide composed of 34 amino acid residues. It exhibits a wide spectrum antimicrobial activity against Gram-positive bacteria and is suitable for food preservation. In order to protect nisin from the interaction with food components and to ensure the stability of antimicrobial peptide during food processing and storage period, the preparation of nisin-loaded pectin nanoparticles in the simple and low cost way based on the complexation method is presented. Three types of pectin biopolymer were tested and found that the methoxylation degree of pectin influenced on the nisin loading efficiency and particle size. For the complex formation, both electrostatic and hydrophobic interactions were important. Nisin-loaded pectin nanoparticles exhibited antimicrobial activity dependent on the type of biopolymer. In view of particle size and antimicrobial activity, nisin-loaded pectic acid nanoparticles were identified as the most suitable and perspective to be used in food industry as an antimicrobial system.
Electronic Journal of Biotechnology, 2014
Background: The roots of chicory and the tubers of Jerusalem artichoke are used for the productio... more Background: The roots of chicory and the tubers of Jerusalem artichoke are used for the production of inulin. However, a quality of tubers and roots, i.e. the content of inulin, monosaccarides and disaccharides, depends on the activity of enzymes implicated in the metabolism of inulin. The knowledge on the changes of activities of inulin synthesizing and degrading enzymes is limited during plant sprouting, growth and dormancy. It happens due to complicated measurements of the product of enzymatic reaction in the presence of crude plant extract. Fructan exohydrolase (β-D-fructan fructohydrolase, FEH, EC 3.2.1.80) is an enzyme responsible for the hydrolysis of fructans in plants. For fructose as the reaction product measurement, a high-performance liquid chromatography is usually used. The aim of the study was to choose a simple and suitable method for FEH activity determination and the measurement of fructose in the presence of plant extracts. Results: Two chemical methods, i.e. copper(II)-neocuproine and 3,5-dinitrosalicylic acid, and the enzymatic one based on the reactions catalyzed by hexokinase, phosphoglucose isomerase and glucose-6-phosphate dehydrogenase were used. Enzymatic method was found to be suitable for FEH activity determination in plant extracts, and on the contrary to chemical methods no interference effects of compounds from crude plant extracts were observed. Conclusion: Enzymatic method is applicable for the routine analysis and will allow performing the investigations without special equipment on the inulin degrading enzyme in biotechnologically important crops.
European Polymer Journal, 2015
Abstract One-pot successive three-step RAFT polymerization of 2-hydroxyethyl methacrylate (HEMA) ... more Abstract One-pot successive three-step RAFT polymerization of 2-hydroxyethyl methacrylate (HEMA) and butyl methacrylate (BMA) in the presence of difunctional RAFT CTA is reported demonstrating successful synthesis of pentablock copolymers containing hydrophilic blocks of pHEMA separated by hydrophobic blocks of pBMA. Dispersity of pentablock copolymers was lower than that of pHEMA and triblock copolymers, down to 1.11. pHEMA blocks of the pentablock copolymer were decorated by pendent butylthiocarbonothioylthio moieties, which served as multiple RAFT CTA for grafting of acrylic acid (AA). The resulting anionic pentablock brush copolymers consisting of three brush blocks separated by linear blocks were characterized by SEC with triple detection and 1 H NMR spectroscopy. Pentablock brush copolymers with short pAA side chains produced aggregates at low pH and showed conformational changes during titration with alkaline solution, while those with medium-length pAA side chains showed ionization behavior typical for anionic molecular brushes. Anionic pentablock brush copolymers are mimicking naturally occurring molecular brushes and deserve attention as potential surface modifiers and lubricants.
European Polymer Journal, 2010
Conventional free-radical and RAFT copolymerization of poly(ethylene oxide) substituent containin... more Conventional free-radical and RAFT copolymerization of poly(ethylene oxide) substituent containing methacrylate macromonomers, PEO 5 MEMA and PEO 45 MEMA, was studied by the use of 1 H NMR spectroscopy for an analysis of residual monomers. From the monomer consumption curves, several parameters including monomer conversion, instantaneous copolymer composition and reactivity ratios of the monomers were evaluated. Reactivity ratios of PEO 5 MEMA and MAA estimated by non-linear approach of error-in-variables model and presented as joint confidence regions were constant during conventional free-radical and RAFT copolymerizations of the above monomers but were slightly affected by the RAFT process. Reactivity ratio of PEO 45 MEMA was found to be lower than that of PEO 5 MEMA and varied during copolymerization: increased with conversion in conventional free-radical copolymerization and slightly (without confidence) decreased in the RAFT process. RAFT copolymerization of PEO 45 MEMA and MAA enabled to synthesize comb copolymers with low composition distribution and more homogeneous distribution of PEO side chains along the mainchain. Under copolymerization with MAA, PEO 45 MEMA behaved like typical macromonomer with appropriate steric hindrance while the behavior of PEO 5 MEMA was similar to that of a low-molecular methacrylate.
Acta Physiologiae Plantarum, 2013
ABSTRACT The data on the composition of carbohydrates in Jerusalem artichoke tubers harvested at ... more ABSTRACT The data on the composition of carbohydrates in Jerusalem artichoke tubers harvested at the end of March after being exposed to frost during winter in soil were presented. The analysis of carbohydrates was also performed during the following period of vegetative growth and intensive photosynthetic activity in summer. Moreover, the composition of carbohydrates in spring tubers was compared with the one in autumn tubers. The tubers of three cultivars Sauliai, Albik and Rubik were applied for the analysis. The amount of fructooligosaccharides in the spring tubers of all cultivars was equal approximately to 80 % of dry matter. The similar amount of fructooligosaccharides was determined in the autumn tubers of both Sauliai and Albik. In Rubik tubers, their amount was about 10 % higher. The average degree of fructooligosaccharides polymerization differed. In the spring tubers of all cultivars, it was equal to three. In the autumn tubers of Sauliai, Albik and Rubik it was equal to 6, 9 and 10, respectively. The highest amount of sucrose equal to 14–18 % depending on the cultivar was found in the spring tubers. The autumn tubers had the low amount of sucrose (1.4–4.3 %), glucose (0.07–0.18 %) and fructose (0.35–0.5 %). The data on the composition of carbohydrates showed that the tubers of Jerusalem artichoke can be harvested in autumn or left in soil for overwintering. However, they should be used for different purposes due to different carbohydrates composition.
European Polymer Journal, 2010
Novel cationic polyelectrolytes with a brush-on-brush structure of poly(ethylene oxide) (PEO) sid... more Novel cationic polyelectrolytes with a brush-on-brush structure of poly(ethylene oxide) (PEO) side chains and a charge-containing polyacrylate backbone were synthesized. The PEO side chains were not directly attached to the backbone but via polymethacrylate spacers, thus locating the PEO chains a distance away from the charged units of the backbone. The cationic brush-on-brush polyelectrolytes with high density of PEO chains
Journal of Molecular Structure, 2021
Abstract β-Carotene is insoluble in water, and the complexation of β-carotene with chitooligosacc... more Abstract β-Carotene is insoluble in water, and the complexation of β-carotene with chitooligosaccharides or 2-hydroxypropyl-β-cyclodextrin is one of the strategies to resolve the problem. We present both experimental and theoretical studies for three type solid-state samples: β-carotene, β-carotene/chitooligosaccharides and β-carotene/2-hydroxypropyl-β-cyclodextrin. The prepared samples were analysed by using Raman spectroscopy. The Raman ν1 band shift of β-carotene molecules in cyclodextrins or chitooligosaccharides were observed. The β-ring dihedral angle analysis showed there were three major typical all-trans-β-carotene conformers (trans-trans, trans-cis, cis-cis) which have ν1 shifted by 4 cm−1 according to each other. The study is helpful for better understanding of correlations between Raman ν1 band and Cars distortions.
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Papers by Tatjana Krivorotova