CMV - laboratoř biokoloidů
Browse
Recent Submissions
- ItemEdible films from carrageenan/orange essential oil/trehalose—structure, optical properties, and antimicrobial activity(MDPI, 2021-02-01) Jančíková, Simona; Dordevič, Dani; Sedláček, Petr; Nejezchlebová, Marcela; Treml, Jakub; Tremlová, BohuslavaThe research aim was to use orange essential oil and trehalose in a carrageenan matrix to form edible packaging. The edible packaging experimentally produced by casting from an aqueous solution were evaluated by the following analysis: UV-Vis spectrum, transparency value, transmittance, attenuated total reflectance Fourier-Transform spectroscopy (FTIR), scanning electron microscopy (SEM) and antimicrobial activity. The obtained results showed that the combination of orange essential oil with trehalose decreases the transmittance value in the UV and Vis regions (up to 0.14% +/- 0.02% at 356 nm), meaning that produced films can act as a UV protector. Most produced films in the research were resistant to Gram-positive bacteria (Staphylococcus aureus subsp. aureus), though most films did not show antibacterial properties against Gram-negative bacteria and yeasts. FTIR and SEM confirmed that both the amount of carrageenan used and the combination with orange essential oil influenced the compatibility of trehalose with the film matrix. The research showed how different combinations of trehalose, orange essential oils and carrageenan can affect edible film properties. These changes represent important information for further research and the possible practical application of these edible matrices.
- ItemAccumulation of Poly(3-hydroxybutyrate) Helps Bacterial Cells to Survive Freezing(PLoS, 2016-06-17) Obruča, Stanislav; Sedláček, Petr; Mravec, Filip; Kučera, Dan; Benešová, Pavla; Márová, IvanaAccumulation of polyhydroxybutyrate (PHB) seems to be a common metabolic strategy adopted by many bacteria to cope with cold environments. This work aimed at evaluating and understanding the cryoprotective effect of PHB. At first a monomer of PHB, 3-hydroxybutyrate, was identified as a potent cryoprotectant capable of protecting model enzyme (lipase), yeast (Saccharomyces cerevisiae) and bacterial cells (Cupriavidus necator) against the adverse effects of freezing-thawing cycles. Further, the viability of the frozen-thawed PHB accumulating strain of C. necator was compared to that of the PHB non-accumulating mutant. The presence of PHB granules in cells was revealed to be a significant advantage during freezing. This might be attributed to the higher intracellular level of 3-hydroxybutyrate in PHB accumulating cells (due to the action of parallel PHB synthesis and degradation, the so-called PHB cycle), but the cryoprotective effect of PHB granules seems to be more complex. Since intracellular PHB granules retain highly flexible properties even at extremely low temperatures (observed by cryo-SEM), it can be expected that PHB granules protect cells against injury from extracellular ice. Finally, thermal analysis indicates that PHB-containing cells exhibit a higher rate of transmembrane water transport, which protects cells against the formation of intracellular ice which usually has fatal consequences.
- ItemThe Role of Concentration and Solvent Character in the Molecular Organization of Humic Acids(MDPI AG, 2016-10-21) Klučáková, Martina; Věžníková, KateřinaThe molecular organization of humic acids in different aqueous solutions was studied over a wide concentration range (0.01–10 g/dm3). Solutions of humic acids were prepared in three different media: NaOH, NaCl, and NaOH neutralized by HCl after dissolution of the humic sample. Potentiometry, conductometry, densitometry, and high resolution ultrasound spectrometry were used in order to investigate conformational changes in the humic systems. The molecular organization of humic acids in the studied systems could be divided into three concentration ranges. The rearrangements were observed at concentrations of ~0.02 g/dm3 and ~1 g/dm3. The first “switch-over point” was connected with changes in the hydration shells of humic particles resulting in changes in their elasticity. The compressibility of water in the hydration shells is less than the compressibility of bulk water. The transfer of hydration water into bulk water increased the total compressibility of the solution, reducing the ultrasonic velocity. The aggregation of humic particles and the formation of rigid structures in systems with concentrations higher than 1 g/dm3 was detected.
- ItemQuantitative Raman Spectroscopy Analysis of Polyhydroxyalkanoates Produced by Cupriavidus necator H16(MDPI, 2016-10-28) Obruča, Stanislav; Sedláček, Petr; Benešová, Pavla; Kučera, Dan; Márová, IvanaWe report herein on the application of Raman spectroscopy to the rapid quantitative analysis of polyhydroxyalkanoates (PHAs), biodegradable polyesters accumulated by various bacteria. This theme was exemplified for quantitative detection of the most common member of PHAs, poly(3-hydroxybutyrate) (PHB) in Cupriavidus necator H16. We have identified the relevant spectral region (800-1800 cm(-1)) incorporating the Raman emission lines exploited for the calibration of PHB (PHB line at 1736 cm-1) and for the selection of the two internal standards (DNA at 786 cm(-1) and Amide I at 1662 cm(-1)). In order to obtain quantitative data for calibration of intracellular content of PHB in bacterial cells reference samples containing PHB amounts determined by gas chromatography from 12% to 90% (w/w) were used. Consequently, analytical results based on this calibration can be used for fast and reliable determination of intracellular PHB content during biotechnological production of PHB since the whole procedure from bacteria sampling, centrifugation, and sample preparation to Raman analysis can take about 12 min. In contrast, gas chromatography analysis takes approximately 8 h.
- ItemDetermination of Critical Parameters of Drug Substance Influencing Dissolution: A Case Study(Hindawi Publishing Corporation, 2014-09-15) Bojňanská, Erika; Kalina, Michal; Pařízek, Ladislav; Bartoníčková, Eva; Opravil, Tomáš; Veselý, Michal; Pekař, Miloslav; Jampílek, JosefThe purpose of this study was to specify critical parameters (physicochemical characteristics) of drug substance that can affect dissolution profile/dissolution rate of the final drug product manufactured by validated procedure from various batches of the same drug substance received from different suppliers.The target was to design a sufficiently robust drug substance specification allowing to obtain a satisfactory drug product. For this reason, five batches of the drug substance and five samples of the final peroral drug products were analysed with the use of solid state analysis methods on the bulk level. Besides polymorphism, particle size distribution, surface area, zeta potential, and water content were identified as important parameters, and the zeta potential and the particle size distribution of the drug substance seem to be critical quality attributes affecting the dissolution rate of the drug substance released from the final peroral drug formulation.