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Preparation of humic hydrogels for appliaction in cosmetics
Pavlicová, Renata ; Mravec, Filip (referee) ; Sedláček, Petr (advisor)
This bachelor´s thesis is focused on the preparation and characterization of hydrogels containing humic substances and assessment of their potential usefulness in cosmetic practice. Main objective of the work was to develop a literature review focusing on the potential use of humic substances in the cosmetics and pharmaceutical industries. Furthermore, the aim was to prepare model hydrogels addition of soluble humic substances in traditional cosmetic compositions and their characterization by basic methods of analysis parameters. The main investigated parameters were consistency resulting gels (assessed subjectively and subsequently by rheology), their internal pH and dry matter. The experimental results showed that incorporation of humic substances into hydrogels resulting gels acceptable characteristics for further use in cosmetic applications.
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New Methods of Cross-linking of Humic Substances
Lepíková, Jana ; Sedláček, Petr (referee) ; Kalina, Michal (advisor)
This bachelor thesis was focused on the study of crosslinking of humic substances. The main aim of this work was to find and optimize utilization of new crosslinking agents for humic acids. Commercial product – lignohumate – was also used in the work as comparative sample. Two groups of crosslinking agents were studied in this work – multivalent metals (CaCl2, MgCl2) and citric acid. In all cases the studied hydrogels were cross-linked by means of chemical valences. All prepared hydrogels were characterized using the determination of their inner pH, density and concent of dry matter. The process of aging of hydrogels – syneresis – was also studied. The main experimental method applied for hydrogels characterization was rheology. Prepared hydrogels represent interesting materials for following studies and also for possible future practical applications.
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Microbial production of extracellular polymers and their involvement in stress response
Müllerová, Lucie ; Sedláček, Petr (referee) ; Obruča, Stanislav (advisor)
Bachelor’s thesis is focused on the production of extracellular polysaccharide pullulan by microorganism Aureobasidium pullulans, purification of pullulan and its possible use as a cryoprotectant. As a part of this work a description of A. pullulans, pullulan and an overview of involvement in its stress response were provided. In the experimental part growth characteristics of A. pullulans (the strain CCM 8182 was used) and pullulan production during growth in optimal conditions was analyzed. Biomass production was the highest with fructose as a carbon source (3,580 g/l CCM 8182), the highest pullulan production occurred when using sucrose as a carbon source (10,300 g/l F 148). Among three organic solvents used for pullulan precipitation – ethanol, acetone, isopropylalcohol, ethanol was selected as the best for further experiments in ratio 1:2 (fermentation broth:ethanol). Pullulan purity was characterized by HPLC. As a further part of this work, cryoprotectant properties of pullulan at temperatures – 72° C, -18° C, 4° C and 60°C were studied. The presence of pullulan at temperatures – 72° C and 60° C was found to be detrimental to cell viability. At temperatures – 18° C and 4° C the cryoptotectant activity of the polysaccharide was confirmed.
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Involvement of polyhydroxyalkanoates in stress response of bacteria during late stationary phase
Šuráňová, Zuzana ; Sedláček, Petr (referee) ; Obruča, Stanislav (advisor)
The aim of this work was to study the involvement of polyhydroxyalkanoates into stress response of bacteria in the late stationary phase. Bacteria Cupriavidus necator H16 (able to produce PHA) and bacteria Cupriavidus necator H16/PHB-4 (unable to produce PHA) were used for the experiment. In the theoretical part, the polyhydroxyalkanoates and a stress response of bacteria were reviewed. In the experimental part of the work, the involvement of polyhydroxyalkanoates into stress response of bacteria in the late stationary phase against selected stress factors was studied. A resistence against various stress conditions of bacteria was studied. During long term cultivations a culture viability as well as PHA distribution among bacterial populations were assessed by using flow cytometry and the PHA content in biomass was analyzed by gas chromatography with FID detector.. Based on the results obtained in this work, it was found that the PHA acumulating bacteria Cupriavidus necator H16 is capable to survive carbon substrate limitations better than the bacteria Cupriavidus necator H16/PHB. Further, Cupriavidus necator H16 also revealed higher resistence against various stress factors such as ethanol treatment and freezing.
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The Study of Biopolymers Stability Using Light Scattering Techniques
Kratochvíl, Zdeněk ; Sedláček, Petr (referee) ; Kalina, Michal (advisor)
The stability of chosen biopolymers (or simple carbohydrates and amino acids) was in-vestigated using light scattering methods. Samples were prepared by dissolving the sub-stance in deionised water or in diluted acetic acid. Firstly, the effect of increasing concen-tration on zeta potential was observed and the optimal concentration for the next measure-ments was determined. Afterwards, the stability and the molecular weight of used sub-stances were studied during long-time storage in different time intervals. It was found out that chitosan, CMC, hyaluronate and sodium alginate were subjected to degradation whereas increase of the molecular weight and the zeta potential was observed in case of BSA. In the end, the samples were exposed to several different external effects, namely the influence of different temperatures, UV radiation and increasing ionic strength. The results showed that rather higher temperature has a significant impact on biopolymers stability. However, used biopolymers were hardly affected by UV radiation except BSA whose molecular weight increased considerably. Decrease of the zeta potential absolute values and the molecular size usually occurred with increasing ionic strength. The change of molecular weight was not detected.
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Study on structural and thermodynamic aspects of the interactions of humic substances with organic ions.
Fryšová, Eva ; Pekař, Miloslav (referee) ; Sedláček, Petr (advisor)
This bachelor thesis deals with the study of thermodynamic and structural aspects of the interactions of humic acids with organic ions. Methylene blue (dye) was used as a model organic ion. The interactions were studied by isothermal titration calorimetry and dialysis in diffusion cells. The calorimetric experiments showed exothermic nature of the interactions. Furthermore it was proved that increasing concentration of humic acids causes increasing of reaction enthalpy. The dialysis experiments found that increasing concentration of humic acids causes increasing of apparent equilibrium constant. The value of this constant was lower for modified humic acid due to the reduced content of the binding sites.
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Microrheology with Fluorescence Correlation Spectroscopy
Kábrtová, Petra ; Sedláček, Petr (referee) ; Mondek, Jakub (advisor)
A comparison of three passive microrheological techniques was made with the emphasis on FCS. Fluorescently labelled and unlabelled polystyrene particles were used to probe a microrheological response of glycerol solutions, Mili-Q water and sodium hyaluronate solutions. In addition, for FCS technique an approximated equation for calculation of MSD values was derived and verified. It was found that FCS outmatches current microrheological techniques of DLS and video-based particle tracking by its ability to gain a broader data range including the area in which, until now, it was impossible to describe a microrheological behaviour of samples reliably.
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Interactions between hyaluronan and cetrimide
Adamcová, Zuzana ; Sedláček, Petr (referee) ; Mravec, Filip (advisor)
Interactions between hyaluronan and cationic Cetrimide were studied using fluorescence spectroscopy and turbidimetry in model physiological solution (0,15 M NaCl) and water. Results obtained in water showed strong electrostatic interactions before reaching CMC of the surfactant, which were screened in presence of salt due to high ionic strenght of the solution. Behavior of Cetrimide-hyaluronan systems was compared with the pure TTAB in equivalent system. It was found, that changes in Cetrimide-HA system occure at lower concentrations of the surfactant than in TTAB-HA system. This was probably caused by presence of small amount of CTAB in Cetrimide.
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Determination of acidic groups in humic substances.
Kabeláčová, Kateřina ; Sedláček, Petr (referee) ; Janeček, Jiří (advisor)
Within this bachelor thesis we compared three method to determine the acidity of humic substances. We employed the baryta-method (which determines the total acidity), the Ca-acetate method (determines the content of carboxylic groups only) and the technique of Ray von Wandruszka. This method should provide the content of groups dissociable at pH>12. We used four different samples of humic acids isolated from two sources (lignite and peat). While the differences between results of baryta and Ca-acetate methods were expected and can be easily explained, the values of acidity obtained by the von Wandruszka method represent roughly one half of the results of Ca-acetate method and almost only ten percent of the baryta results. In the cases of baryta as well as von Wandruszka methods we observed a dependency of the results on the time-length of the analysis. In the theoretical part the characterisation, divided, creation, structure and properties of humic substances are summarized. In the end of theoretical part are described using method for analysis of humic acids.
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