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Preparation and characterization of lignin modified by laccase enzyme
Hrušková, Lucie ; Obruča, Stanislav (referee) ; Kalina, Michal (advisor)
This master’s thesis focuses on the enzymatic modification of commercially available lignin using laccase enzyme and monitoring its impact on selected physical and chemical properties. Lignin is an attractive material for the production of renewable chemicals, materials, and energy, but its complex chemical structure poses a major obstacle to its effective utilization. Enzymatic modification appears to be a promising solution for its processing. Experiments were conducted under various conditions, such as pH, enzyme dosage, and reaction time. In the subsequent part of the experiment, the modified lignins were characterized and their results compared with those of the raw kraft lignin before modification. Molecular weight was determined using SEC-MALS, and the concentration of phenolic groups and antioxidant activity were measured. Structural changes were also monitored using FTIR. The results indicate that the enzymatic modification of lignin using laccase led to an increase in the molecular weight of the modified lignins, along with a decrease in the content of phenolic groups and a reduction in antioxidant activity. Based on the obtained results, it can be concluded that the action of the laccase enzyme resulted in lignin polymerization and the formation of new chemical bonds, leading to further aggregation.
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Synthesis of Mineral Oils by Oligomeration of 1-alkenes
Porubský, Tomáš ; Kučera, František (referee) ; Petrůj, Jaroslav (advisor)
The theoretical part presents a summary of existing information and procedures for the oligomerization of 1 alkenes. It also introduces suggestion of the new method for preparing poly(1-hexene) by controlled or living polymerization with nitroxyl radicals. In the experimental part was synthesized oligomer of 1-hexene with DBP or AIBN radical initiators and coordination Ziegler-Natta catalysts, which consisted of TiCl4 and organometallic compounds TIBA or TNHA. GC/MS analysis of the radical polymerization reaction mixture, showed no oligomer formation even after 6 hours. Effect of Ti/Al ratio, temperature and type of organoaluminium compund on conversion and molecular weight were investigated. Reaction products were analyzed by 1H NMR and GC/MS spectrometry. Results showed that the obtained oligomer was a mixture of oligomers with a degree of polymerization 2-9 and average molecular weight of 220-270 g/mol. Monomer conversion reached values of 72 98 %.
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Study of the adheisve affinity into the wood cell wall at the sub-microstructural level
Mitrenga, Ondřej ; Rovnaník, Pavel (referee) ; Vaněrek, Jan (advisor)
This thesis focuses on the problematic of adhesive affinity into wood cell wall at the sub-microstructural level. The main subject of this thesis is research work of scholarly articles focused on the penetration of resins and polymers into the cell wall of the wood. In contains a description of the principles on which the used methods are based, and a summary of the results achieved. In the experiment, several method were used to investigate the possible penetration of selected methods adhesives into the structure of the cell wall. These are fluorescence microscopy, confocal microscopy, scannin electron microscopy (SEM) and transmission electron microscopy (TEM).
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Automatic improvements of images from 1D gel electrophoresis
Kovář, Martin ; Vítek, Martin (referee) ; Škutková, Helena (advisor)
In this bachelor’s thesis are explained the basic principles of electrophoresis and its modalities with focusing on 1D gel electrophoresis. It describes analysis of an electrophoreogram and causes of its possible distortion, and states specifications of applications of the method in microbiology, genomics and proteomics. The practical part presents development, optimization and outputs of a programme for automatic electrophoreogram analysis, which was created in Matlab environment. The analysis contains lane and band detection and computation of samples’ molecular weight. The ending of the thesis is constituted by evaluating efficiency of detection and accuracy of weight computation.
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interaction of adhesive with structural wood
Janová, Petra ; Rovnaník, Pavel (referee) ; Vaněrek, Jan (advisor)
This labor is based on penetration of adhesives into a wood cell walls. It focuses mainly on adhesives that are currently used for construction purposes. It also contains a methodics of selecting adhesives and wood, which will be used for glued joints and summarizes the methods used for detect these adhesives in the wood cell wall. It experimentally verifies the appropriate selection of the dye-solvent combination used in the adhesive.
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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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Influencing of molecular mass of hyaluronic acid by fermentation process
Wikarská, Monika ; Jílková, Jana (referee) ; Velebný, Vladimír (advisor)
The biological function of hyaluronic acid (HA) – the polysaccharide, which consists of repeating units of N-actylglucosamine and glucuronic acid – is extremely broad and often contradictory, depending on its molecular weight (MW). The bacterial production provides HA of high molecular weight and purity. The objective of this thesis is to control the molecular weight of produced HA by the addition of hyaluronidases during the process of fermentation, resulting in reduction of viscosity of the medium followed by increase of yield. Hyaluronic acid was prepared by batch fermentation of the microorganism Streptococcus equi subsp. zooepidemicus. During the process of fermentation, the enzyme hyaluronate 4-glycanohydrolase (BTH) at various concentrations and different times of cultivation was added to bioreactors. The HA yield, the molecular weight and the polydispersity by the SEC-MALLS were monitored, together with the residual glucose concentration and the dynamic viscosity of the production medium. The formation of low and medium molecular weight HA was achieved. The addition of 10 U (BTH) / g (HA) had no significant effect on the molecular weight and therefore the HA function, but the corresponding drop of viscosity was noteworthy for the simplification of the product purification. Potential increase in HA yield was not confirmed because of the very low concentration of residual glucose and the method of precipitating low and medium MW HA.
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Physical ageing of polypropylene
Weiss, Jiří ; Kučera, Jaroslav (referee) ; Tocháček, Jiří (advisor)
Physical aging of commercially produced polypropylene homopolymers Mosten was studied. The work is focused on monitoring the changes in physical properties of polymer in the time period 90 days from the date of preparation of the test specimen. The aging of polymers was realized at storage temperatures of 23 and 80 °C. The changes in crystallinity, yield strength, modulus, elongation and impact strength using DSC method, tensile tests and impact tests according to Charpy were monitored. Molecular weight distribution was determined by means of GPC at each polymer. Relationships between the changes in physical properties and polymer molecular weight were sought.
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Study of adhesive penetration into the wood cell wall
Janová, Petra ; Krbila, Jaromír (referee) ; Vaněrek, Jan (advisor)
This labor is based on penetration of adhesive into a wood cell walls. It focuse on adhesives basicly used for construction purposes, especially on epoxy resins. The labor contains the use of methods for precise detection adhesive in wood and methodics for choice of adhesive and wood basically used for bonding. It describes the experimentally detected dependence of contact angle on viscosity epoxy resins.
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