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Hybrid biopolymer composites for 3D printing applications
Menčík, Přemysl ; Bakoš, Dušan (referee) ; Dzik, Petr (referee) ; Jančář, Josef (advisor)
This dissertation work deals with the thermic and the mechanical behavior of plasticized bio-plastics and bio-composites for the 3D printing applications. The influence of plasticizer chemical structure on thermic and mechanical properties of plasticized polymeric blends from the poly-3-hydroxybutyrate and the poly lactic acid was investigated. Used plasticizers are based on derivative of citric acid. The influence of plasticizers on polymeric matrix and their compatibility was estimated by gear torque rate of melt mixer, respectively rate of plasticizer migration from the material during higher temperature. The plasticizer structure influence on the glass transition temperature and on the kinetics of crystallization of plasticized material was investigated by modulated differential scanning calorimetry. The behavior of material during 3D printing was also observed. Mechanical properties of printed samples, especially their elongation at break, were determined by tensile tests. The largest softening effect was observed using tributylcitrate plasticizer, where the glass temperature decreased by 35 °C and elongation at break increased by 150% compared to non-plasticized reference material. This plasticized polymeric blend showed also sufficient 3D printing properties and was used as the matrix for composites in the next part of this work. Composites were filled by kaolin, limestone, halloysit, fumed silica, talc, magnesium hydroxide and chopped flax fibers. Particle distribution in composites in dependence of used surface treatment of filler was observed by scanning electron microscopy. The influence of composite filler on rheological properties, crystallization kinetics and thermal stability of composites, was observed by viscometry and differential scanning calorimetry. Their mechanical properties and heat deflection temperature were observed on samples prepared by 3D print. Kaolin in composite material showed homogeneous particle distribution and insignificant nucleation effect and influence on thermic stability. Composite filled by kaolin also showed 18% smaller warping during 3D printing compared to non-filled reference. Consequently kaolin was evaluated as suitable inorganic filler for bioplastic composite intended for 3D print and this composite was used in the following part of this thesis. Method of mathematical prediction of Young's modulus was described for composite samples prepared by 3D print. Composites filled by one type of filler – kaolin, or limestone, resp. by combination of both fillers were investigated on the basis of the micromechanic Halpin-Tsai model modified by the semiempiric multiparametric Cerny's equation. Additive and combinational method of Young's modulus evaluation is used for composites with hybrid filling. Deflection of measured and theoretical Young's modulus value of composite filled with kaolin was decreased by established correction from 21% to 1% and for composites filled with limestone from 13% to 9%. In this manner it is possible to predict the Young's modulus of the samples prepared by 3D print.
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Ecotoxicological evaluation of selected plastics
Demová, Kristína ; Mravcová, Ludmila (referee) ; Zlámalová Gargošová, Helena (advisor)
The presented bachelor thesis deals with the issue of plastics in the environment and their ecotoxicological evaluation. This topic is currently being brought to the fore due to the development of new, more easily degradable plastics. This is intended to be a solution to the current environmental problem. That is why the aim of this work was to verify the assumption of ecological safety of such plastics. The experimental part focuses on one selected biodegradable plastic - polyhydroxybutyrate, which was evaluated using acute and chronic toxicity tests. The tests were performed in an aquatic arrangement to predict the effect on the aquatic ecosystem. Two organisms were chosen from its representatives, the crustacean Daphnia magna and the plant Lemna minor. The chronic test on the organism Daphnia magna shows the greatest results, which indicates the negative effects of the selected plastic on the tested organism.
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Photoprotective properties of PHB granules
Hesko, Ondrej ; Obruča, Stanislav (referee) ; Mravec, Filip (advisor)
The objective of this work is study and design of physical-chemical methods for verification of photoprotective properties PHB inclusions using bacteria Cupriavidus necator H16 and its mutated bacteria strain Cupriavidus necator PHB-4 which differs in production capability of polyhydroxyalkanoates. Basic information about of polymer inslusions and methods used for proving photoprotectivity are discussed in theoretical part. Methods such as nephelometry and continous fluorescence microphotolysis (CMF), which is used to characterize the mechanism of interaction of light with inclusions, were optimized. In experimental part properties of light scattering in bacteria were determined and characteristic curves were obtained. Further the photostability of fluorescence probe specific for nucleic acids were compared in bacteria strains. This method should prove bigger tolerance of bacteria H16 for UV light. It should also define possible interaction of nucleic acids with PHB inclusions.
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Isolation of PHA from bacterial biomass and their subsequent purification
Zlochová, Barbora ; Kouřilová, Xenie (referee) ; Obruča, Stanislav (advisor)
This bachelor thesis deals with the isolation and characterization of the bacterial polymer PHA isolated from the bacterial strain Halomonas halophila (CCM 3662) by osmotic stress in distilled water, ie hypo shock, when the cells crack and release PHA. The addition of biosurfactants simultaneously solubilizes the proteins and lipids of the residual biomass, theoretically achieving a purer PHB product without the use of toxic substances such as chloroform. The theoretical part of the work focuses on PHA in terms of their general properties and use, the mechanism of synthesis of PHA microorganisms and their subsequent degradation and the existing strategy for isolating PHA from bacterial biomass. The experimental part describes the production of PHB bacteria Halomonas halophila and the subsequent process of isolation of PHB by hypo shock of halophilic bacteria in distilled water with the addition of selected biosurfactants. Biosurfactants used in the work are coconut soap, lecithin, rhamnolipids, sophorolipids, coco glucoside, lauryl glucoside and cocoamidopropyl betaine. The properties of the isolated PHB material were analyzed by gas chromatography with FID detection and SEC-MALS and FTIR methods. Based on the results, we chose the pair of coco glucoside and lauryl glucoside as the most suitable biosurfactants that can be used to isolate PHB from bacterial biomass. In combination with washing the material in ethanol, at concentration of biosurfactant 5 g/l and isolation in 70 ° C, it was possible to achieve a purity of 90 % of material using cocot glucoside and 89 % purity of material using lauryl glucoside.
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Detoxification of lignocellulose hydrolyzates
Vašíčková, Monika ; Pořízka, Jaromír (referee) ; Obruča, Stanislav (advisor)
The aim of this work was study of the detoxification of lignocellulose material hydrolysates and to investigate sawdust suitability as a substrate for microbial production of PHA by bacteria Burkholderia cepacia and Burkholderia sacchari. In the experimental part of the work the most suitable way of detoxification of model and real hydrolysate was studied. After that, detoxification methods used were evaluated. Criteria for evaluation were concentration of polyphenols as the most important microbial inhibitors and reduction saccharides as the main carbon substrate. Furthermore, fermentability of the hydrolysates was also tested by cultivation of two bacteria capable of PHA accumulation. Burkholderia sacchari demonstrated higher ability to accumulate PHA then Burkholderia cepacia. Then in the summary – most effective way for detoxification was ‚overliming‘. Major increase of PHB in biomass was obtained when Burkholderia sacchari was cultivated on media gained by application of overliming of real lignocellulose hydrolysate. However, total gains of PHB were more likely low and then sawdust can not be considered as a substrate for PHB production at industrial scale.
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Preparation and characterization of enzyme-containing wound dressings
Jurová, Bronislava ; Szotkowski, Martin (referee) ; Skoumalová, Petra (advisor)
This diploma thesis is focused on the study and characterization of nanofiber wound dressings from natural biopolymers. Proteolytic enzymes, specifically collagenase and bromelain, were incorporated into these nanofiber covers. The theoretical part deals with a brief description of skin wounds, their healing and skin covers. There are also methods for preparing these covers and the methods used to characterize them. The practical part deals with the optimization of the preparation of nanofiber coatings based on polyhydroxybutyrate, gelatin, alginate and chitosan. These nanofibers were then enriched with active substances and their gradual release into the model environment was monitored. Finally, their proteolytic activity was determined for these substances.
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Development and preparation of antimcrobial nanostructure biomaterials
Drabíková, Nela ; Skoumalová, Petra (referee) ; Márová, Ivana (advisor)
The presented diploma thesis deals with the optimalisation of preparation and the preparation of combined nanostructured antimicrobial biomaterials itself. In the theoretical part, a review focused on used materials and consequently preparation of nanoparticles and nanofibers was elaborated. Furthermore, the used antimicrobial substances – curcumin and ampicillin, and the principle of cytotoxicity assay were described.In practical part the optimalisation process is described. Furthermore the safety of prepared materials and used antimicrobial substances on HaCaT cell line was tested, in order to confirm their possible further use in cosmetic and pharmaceutical industry. Great part of the thesis deals with evaluation of the antimicrobial activity of used substances and prepared combined nanomaterials on multiple microorganisms from grampositive bacteria, gramnegative bacteria and yeasts. Also the release speed of antimicrobial substances from prepared nanomaterials was determined by spectrophotometer. The amount of released ampicillin from prepared nanomaterials was determined by liquid chromatography.
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Preparation of nanoparticles and nanofibers with antimicrobial components
Sosková, Simona ; Veselá, Mária (referee) ; Skoumalová, Petra (advisor)
The presented diploma thesis is focused on the preparation of new materials with antimicrobial effect. Liposomes and nanofibers from polyhydroxybutyrate containing clotrimazole and natural extracts with good antifungal and antioxidant effects were prepared. The theoretical part contains examples and short description of using nanoparticles and nanofibers in cosmetics and medicine and the description of plants which have positive and potential antimycotic effects. Moreover, methods for particles and fibers characterisation were shortly described. In the experimental part, natural water and lipid extracts were prepared and spectrophotometrically characterised for the content of polyphenols, flavonoids and the antioxidant activity. Liposomes and liposomes containtng PHB were prepared from selected extracts and the encapsulation effectivity, shortterm and longterm stability via determination of polyphenols were determined. Prepared particles were characterized with DLS method (size) and zeta- potential (stability). PHB nanofibers functionalised with selected lipid extracts and clotrimazole were prepared via electrospinning and forcespinning, and examined via FLIM and FTIR-ATR methods and spectrophotometry was used for antioxidant activity and release of active substances determination. Antifungal properties of prepared particles, extracts and fibers using the test system Candida glabrata were studied. Finally, cytotoxicity of selected samples was tested with MTT assay using human keratinocytes.
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Polyhydroxyalkanoates and their role in bacterial biofilms
Rucká, Markéta ; Samek,, Ota (referee) ; Obruča, Stanislav (advisor)
This master thesis deals with polyhydroxyalkanoates (PHA) and their role in bacterial biofilms. In the theoretical part the polyhydroxyalkanoates, bacterial biofilm and the relationship between them were reviewed. The experimental part focused on differences in PHA production by planktonic and biofilm cells. In order to study selected topic, bacterial strains of Burkholderia cepacia and Burkholderia sacchari were cultivated using a CDC biofilm reactor. The attention was paid to quantity and especially to the form in which PHA occurs in planktonic and biofilm cells. Results of Raman spectroscopy have shown that PHA exists exclusively in native amorphous form in planktonic bacterial cells. On the other hand, in biofilm PHA occurs also in a partially crystalline form. In addition, the resistance of planktonic and biofilm cells against various stress factors and the effect of osmotic stress on PHA production was tested too. According to the results of the experiment, when the bacteria were exposed to different stress factors (high temperature, low temperature, presence of detergent and so forth) biofilm cells showed a higher stress resistance than planktonic cells. Apart from slowing cell growth and reproduction, increased osmotic pressure in the culture medium also caused decrease of PHA production. In addition, planktonic cells responded to external stimuli more sensitively than biofilm ones.
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Modification of polyurethane by biodegradable poly(hydroxybutyrate)
Kupka, Vojtěch ; Žídek, Jan (referee) ; Vojtová, Lucy (advisor)
Cílem předložené bakalářské práce byla syntéza elastomerního polyuretanu plněného biodegradabilním polyhydroxybutyrátem. Vzorky byly podrobeny analýze morfologie pomocí rastrovací elektronové mikroskopie, mechanické vlastnosti byly testovány jednoosou tahovou zkouškou. Práce se taktéž zabývá předpovědí mechanických vlastností na základě teorií kaučukové elasticity. Bylo zjištěno, že výsledný materiál je částicový kompozit, kde se vzrůstajícím hmotnostním obsahem plniva v materiálu vzrůstá modul pružnosti. Predikce tahových křivek pomocí softwaru SEC.exe ukazovala pro reálný průběh křivky nereálné hodnoty hustot polymerních řetězců. U modelů, které vykazovaly reálné hodnoty hustot, byly naopak hodnoty napětí vyšší, než ve skutečnosti naměřené.
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