Examensarbeten för masterexamen // Master Theses
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- PostAddition of starch in an airlaid process to the cellulose-based composite DuraPulp(2016) Klein, Julia; Chalmers tekniska högskola / Institutionen för kemi och kemiteknik; Chalmers University of Technology / Department of Chemistry and Chemical Engineering
- PostCartilage repair with the use of adipose tissue and 3D bioprinting(2018) attfors, madeleine; Chalmers tekniska högskola / Institutionen för kemi och kemiteknik; Chalmers University of Technology / Department of Chemistry and Chemical Engineering
- PostCharacterization of chocolate microstructure: development and comparison of microscopy techniques to evaluate cocoa butter crystallization(2013) Balestra, Lucile; Chalmers tekniska högskola / Institutionen för kemi- och bioteknik; Chalmers University of Technology / Department of Chemical and Biological Engineering
- PostCharacterization of the 3' untranslated region for optimization of gene expression in yeast(2013) Gizaw, Nebeyu Yosef; Chalmers tekniska högskola / Institutionen för kemi- och bioteknik; Chalmers University of Technology / Department of Chemical and Biological Engineering
- PostDevelopment and validation of a small scale model for assessment of supersaturation and precipitation in simulated gastrointestinal media(2018) Larsson, Olivia; Chalmers tekniska högskola / Institutionen för kemi och kemiteknik; Chalmers University of Technology / Department of Chemistry and Chemical Engineering
- PostDevelopment of fill product with aggressive properties for accelerated storage tests in Tetra Recart(2014) Jansson, Cecilia; Chalmers tekniska högskola / Institutionen för kemi- och bioteknik; Chalmers University of Technology / Department of Chemical and Biological EngineeringTetra Recart (TRC) is a multilayer laminate paperboard package used to package foods such as tomatoes, beans, vegetables and sauces. Some “aggressive” food products interact with the inside of the package material and make it difficult to guarantee the quality of the food during the whole shelf life of the product. Products with pH below 4 and Cl− content above 1% are regarded as “aggressive” and are not packed in the TRC standard material. In this thesis work, a fill product mimicking aggressive food products has been developed. The goal was to obtain the same interaction patterns as given by aggressive food products, but eight times as fast, in order to use the fill product in accelerated storage tests in the development of new TRC materials. The work included the development of a model for corrosion development caused by aggressive products, the design of the fill product, packaging, and opening and evaluation of the packages. As well as evaluating the effects of different concentrations of acids, salts, fat and fatty acid together with an emulsifier, the influence of different storage temperatures on delamination of the inside polymer coating and corrosion of aluminium was evaluated. Delamination of the inside polymer was crucial for an accelerated development of corrosion of the aluminium foil. The presence of free fatty acids and an elevated storage temperature were necessary factors for delamination to occur. A high Cl− content seemed to be more important than a low pH in terms of aggressiveness of a product. The most well suited test product to use in accelerated storage tests of aggressive products in TRC had a pH of 2.49 and a Cl− content of 7.71 %. It was stored at 35°C and contained 40 ppm free fatty acids. This product gave accelerated corrosion, and showed good compliance with the developed model for corrosion development. The composition of the test product is well outside the range for human food, i.e. the food package interactions described in this report would not occur to the same extent with products suitable for human consumption.
- PostDifferentiation of induced pluripotent stem cells to chondrocytes in 3D porous bacterial nanocellulose scaffolds(2014) le Comte, Evelina; Chalmers tekniska högskola / Institutionen för kemi- och bioteknik; Chalmers University of Technology / Department of Chemical and Biological Engineering
- PostEffect of agitation on antimicrobial activity and release during in-vitro testing of antimicrobial wound care dressings(2014) Åkerman, Julia; Chalmers tekniska högskola / Institutionen för kemi- och bioteknik; Chalmers University of Technology / Department of Chemical and Biological EngineeringThe use of antimicrobial substances to combat microorganisms has been in practice for centuries. Louis Pasteur’s germ theory published in 1865 was the first scientific evidence of the link between microorganisms and infectious disease and brought the implementation of antisepsis into hospital routines. The interest in antiseptics diminished with the discovery and introduction of antibiotics in clinical treatment in the 1940s, but the emergence of antibiotic resistance during the past decades has revived the interest in antiseptic agents as treatment of infectious diseases. The aim of this thesis was to evaluate the antimicrobial effect and release kinetics of two commonly used antimicrobial substances (silver and PHMB) during in-vitro testing of antimicrobial wound dressings. Experiments with the active substance in solution as well as experiments with the active substance in the form of antimicrobial wound care dressings were performed. The antimicrobial effect was evaluated using a two-compartment model by determining the number of viable cell counts by standard plate count method. The silver release from wound care dressings was determined by ICP-OES analysis. The PHMB release was assessed with spectrophotometric measurements and a colorimetric method involving the anionic dye Eosin Y. The influence of agitation was evaluated at static conditions and at agitation rates of 50 and 100 rpm respectively. Experiments with active substance in solution against P. aeruginosa showed no influence of agitation on antimicrobial effect. Higher PHMB susceptibility was observed for S. aureus compared to P. aeruginosa, this could be coupled to the outer cell membrane present in gram-negative bacteria which may act as permeability barrier against the polymeric PHMB. In contrast, experiments involving wound care dressings showed a clear correlation between increased antimicrobial effect and increased agitation rates for P. aeruginosa. The contradictive results of the two types of experiments may be explained by the initial mixing of inoculated medium and antimicrobial agent for the experiments with active substance in solution. In the experiments involving wound care dressings no such mixing occurred and hence, the effect of agitation is likely to be greater. The silver release during incubation was similar in experiments performed at static conditions and agitation at 50 rpm, but a significantly higher silver release was detected when agitation at 100 rpm was employed. As no proper control sample was accessible, the amount PHMB released during incubation was not possible to determine with analytical methods available at MHC. Although the presence of interfering substances was indicated in performed measurements of PHMB concentration it could be concluded that agitation does not seem to greatly influence the amount PHMB released, even at higher agitation rates.
- PostEffects of Environmental Educations for Organisations(2017) Strand, Lisa; Mleczkovicz, Rickey; Chalmers tekniska högskola / Institutionen för kemi och kemiteknik; Chalmers University of Technology / Department of Chemistry and Chemical EngineeringThis study investigate what influence an basic environmental education has on an organisation as well as what conditions promotes change. The evaluation focuses on the basic environmental education by Ekocentrum. The main collection of data was done with a survey that was sent to previous participants of Ekocentrum’s education. The survey was completed with seven interviews. The analysis was performed in SPSS and the method which gave best result was comparing mean values. The most important effect of the education found was the change of mindset and the awareness of the environment at the work places. Furthermore, built-on approach of changes were common, instead of more profound changes. Of the different causes investigated, none correlate substantial with the effects of the environmental education. The biggest influence comes from the participants position in the organisation and their level of anticipation towards the education. Besides the investigated factors the setup of the education and the environmental awareness of the management was mentioned in the survey as big influences on the changes made. As this is to be considered as a pilot study there are many possible ways to go through with future studies.
- PostEstablishment and characterization of antibodies against Ciz1b for detection of early-stage lungcancer(2013) Fransson, Emelie; Chalmers tekniska högskola / Institutionen för kemi- och bioteknik; Chalmers University of Technology / Department of Chemical and Biological EngineeringIn Sweden lung cancer is the fifth most common cancer form. One problem with lung cancer is that it often is diagnosed late when the patient already suffers from symptoms, leading to low survival compared to other cancer forms. New and improved screening methods for risk groups could lead to earlier detection of lung cancer and increased survival. Higgins et al. 2012 presented in the article “Variant Ciz1 is a circulating biomarker for early-stage lung cancer” Ciz1b as a new marker for lung cancer. Ciz1b is an alternative splice variant of the normally occurring Ciz1 protein and has been shown to be a promising biomarker for early-stage lung cancer detection being able to distinguish lung cancer patients from healthy individuals. Higgins et al.2012 has done this study using Western blot which is a method not suitable for diagnostic purposes. Therefore they suggest that a method generating simplified quantitative data, such as an ELISA, should be established. The problem to be solved is that there are no Ciz1b specific reagents to be used in ELISA format (Higgins et al., 2012) and therefore this master thesis project was done. The aim of this project was to establish, characterize and evaluate antibodies specific for detection of Ciz1b to be used in ELISA format. Ciz1b is an alternative splicing of Ciz1 where eight amino acids have been spliced. To be able to generate antibodies directed toward this small splice site site-specific immunization was used with phage particles. Filamentous phages were used to express Ciz1/Ciz1b specific peptides on the phage surface by phage display to generate an immune response against specific regions of the Ciz1/Ciz1b proteins, such as the Ciz1b-specific splice site. Phage particles used for immunization were analyzed to verify that the recombinant peptides were located in desired reading frame and that the recombinant pVIII molecules were expressed on the phage surface. The phage particles were immunized in Balb/c female mice several times and blood samples were collected from tail vein. An ELISA was established to analyze anti-Ciz1/Ciz1b titer in blood samples to verify which mice raised an immune response against Ciz1/Ciz1b. Mice with anti-Ciz1/Ciz1b titer were used for hybridoma technology. Five mice had anti-Ciz1/Ciz1b titer; two were used for hybridoma technology. From the hybridoma technology 15 hybridomas show selectivity towards Ciz1b. Those hybridomas produce antibodies with promising specificity against Ciz1b but further analysis has to be done to verify the specificity.
- PostEvaluating the Freeform Reversible Embedding of Suspended Hydrogels bioprinting method(2018) Olsson, Wictor; Chalmers tekniska högskola / Institutionen för kemi och kemiteknik; Chalmers University of Technology / Department of Chemistry and Chemical Engineering
- PostEvaluation of reversed phase liquid chromatography columns ion pair reagents and separation conditions - for stability studies of modified RNA(2016) Sjöstrand Dahlberg, Jacob; Chalmers tekniska högskola / Institutionen för kemi och kemiteknik; Chalmers University of Technology / Department of Chemistry and Chemical Engineering
- PostHydrogels as scaffolds for stem cell therapy with focus on cartilage(2023) Forsell, Oliver; Chalmers tekniska högskola / Institutionen för kemi och kemiteknik; Chalmers University of Technology / Department of Chemistry and Chemical Engineering; Ström, Anna; Ström, AnnaOsteoarthritis, a disease arising from degradation of articular cartilage in joints, presents a major cost for the healthcare system and is a leading reason behind work disability. Conventional therapies are temporary fixes with limited applications and an inability to fully restore the damaged tissue. In recent years, cell therapy has emerged as an alternative and regenerative cartilage therapy. Challenges remain in developing proper scaffolds which serve the purpose of protecting the cells and preventing migration while providing the right mechanical and biochemical signals ensuring high cell viability, proper differentiation and phenotype maintenance. In this study, hydrogel scaffolds were formulated with the objective to achieve both sufficient biochemical and mechanical properties by attempting to create an interpenetrating network (IPN) of polymers forming physical and covalent crosslinks. To determine whether an IPN could be obtained, gels with a variety of crosslinking degrees and polymer concentrations were formulated using a Box-Behnken design of experiments. The gelation kinetics were investigated using a rheometer and molded gels were mechanically tested with a universal testing machine as well as structurally characterized by fluorescent microscopy. A positive synergistic effect was observed with respect to the torsional elasticity but not for unconfined axial compression. Microstructure analysis revealed impact of polymer type and concentration on dispersion quality.
- PostImproved Co-Fermentation of Xylose and Glucose by Encapsulation of Saccharomyces Cerenvisiae(2013) Coelho, Aires; Chalmers tekniska högskola / Institutionen för kemi- och bioteknik; Chalmers University of Technology / Department of Chemical and Biological EngineeringAbstract Background: Presently the consumption of biofuels is increasing substantially. Fermenting lignocellulosic materials could be a cheap, environmentally friendly and sustainable solution to obtain biofuels like bioethanol, without the controversies arising from the use of potential food and feed sources. To access the fermentable sugars of the lignocellulosic matter, pre--‐treatment and hydrolysis must be performed. After these steps inhibitory compounds are present and can interfere with the fermentation. Encapsulation of yeast is a promising technique when the goal is to improve the fermentation productivity and dealing with lignocellulosic inhibitors, like furfural and hydroxymethylfurfural (HMF). Results: The encapsulation was performed with alginate--‐chitosan--‐alginate multilayer capsules. Therefore capsules were treated with 1.5% hydrolysed (3--‐Aminopropyl) triethoxysilane. Fermenting a 40 g/L initial sugars concentration the consumption rate for encapsulated yeast using glucose and xylose was: 1.2 g/gh and 0.3 g/gh in the presence of 1 g/L furfural; with 2 g/L furfural the consumption reached 1.3 g/g h and 0.2 g/gh and without inhibitor 1.5 g/gh and 0.6 g/gh for glucose and xylose respectively. Moreover the ethanol productivity for encapsulated cells using glucose and xylose together was higher, around 50%, when compared with free cells. It was also shown that the volumetric mass transfer coefficients of glucose and xylose have similar values, 3.30 and 3.45 cm3/min respectively. Conclusion: Encapsulation revealed to be efficient in promoting the co--‐consumption of C5 and C6 carbon sugars by recombinant Saccharomyces cerevisiae. There were visible improvements in ethanol yield in encapsulated cultures with glucose and xylose. Encapsulation also showed effectiveness in the presence of furfural.
- PostImproved utilization of waste resources from the pulp and paper mill Nordic Paper Bäckhammar and isolation of local freshwater microalgae species(2014) Svensson, Mikael; Chalmers tekniska högskola / Institutionen för kemi- och bioteknik; Chalmers University of Technology / Department of Chemical and Biological EngineeringThis master thesis was performed during a full academic year and aimed at investigating the possibilities in utilizing otherwise discarded biosludge as a source of nutrients for algal cultures. This work was done as a part of a project cofounded by Vinnova and ÅF in collaboration with the Swedish pulp and paper mill Nordic Paper Bäckhammar (NPB) and SP, Technical Research Institute of Sweden (SP). Biosludge was chosen as a possible source as it is produced in situ en masse and contained a large mass fraction of nitrogen (2.8 % g/g). Biosludge was pre-treated with acids, bases and ultrasonication prior to experiments to determine an effective method for nutrient leaching. Acid pre-treatment showed promising results and was chosen as a suitable method for further development during this project. A screening was performed to evaluate the effect of heat and time versus leached nutrient concentrations from biosludge in HCl-solutions. The results indicated that a high temperature, 120 °C and a long reaction time, 24 h, reached the highest concentrations of NH4+ (19 mg/l) and PO43- (60 mg/l). The highest concentration of NO3- was 64 mg/l, reached after 170 h at 25 °C. The volume was kept constant during all leaching experiments. Water samples were collected at NPB for isolation of microalgae, which were cultivated and stored in minimal laboratory medium, 3N-BBM+V. Algae monocultures were isolated via serial dilution and plate streaking. Based on a visual examination, 7 different morphologies were found among the isolated cultures: Phormidium sp, Oscillatoria sp, Coenococcum sp, Scenedesmus dimorphus, Scenedesmus quadricauda, Chlorella vulgaris and Monoraphidium contortum. S. quadricauda and C. vulgaris could grow in treated biosludge-based medium. C. vulgaris, S. dimorphus and M. contortum showed fast growth rates in 3N-BBM+V medium and 15 % CO2, with growth rates of 0.065, 0.064 and 0.054 h-1 respectively. The total lipid content were determined for the algae strains in selected conditions and it was found that M. contortum could contain as much as 45 % lipids with a fatty acid composition suitable for biofuel production.
- PostIncreased folate content in bread by pre-treatment of Baker´s yeast(2014) Khuu, Hoa Van; Chalmers tekniska högskola / Institutionen för kemi- och bioteknik; Chalmers University of Technology / Department of Chemical and Biological Engineering
- PostInestigation of seedpowder technology for pre-crystallization processing of dark chocolate - Effect on fat crystal structure and storage stability(2014) Lindecrantz, Anna; Chalmers tekniska högskola / Institutionen för kemi- och bioteknik; Chalmers University of Technology / Department of Chemical and Biological EngineeringThe biggest cause of loss in the chocolate industry is the development of fat bloom in chocolate products. Resistance to fat bloom and deterioration is highly linked to the crystal structure of the cocoa fat in chocolate. A chocolate with a stable crystal structure gets properties such as increased resistance to heat and fat bloom, good moulding, a glossy surface and a good snap. In order to achieve a structure with these properties the chocolate must undergo a pre-crystallization process. The most common precrystallization process today is the conventional tempering but a novel and simpler process is the use of seedpowder. The aim of this Master of science thesis was to investigate the potential and usage of three different seedpowders (cocoa butter βVI, cocoa butter βV and chocolate βV) for optimal pre-crystallization of chocolate. Evaluation of the powders was done with respect to reproducibility and robustness of the process, generated crystal structure of the chocolate as well as fat bloom development and fat migration during storage. The results showed that all seedpowders can be used for pre-crystallization of chocolate and depending on the production and what the chocolate will be used for different seedpowder is preferred. The cocoa butter βVI offer a less temperature sensitive production resulting in less powder needed and easier moulding. The cocoa butter βV showed slightly better resistance to fat migration, which is a desired property in chocolate pralines. The chocolate βV powder on the other hand does not change the composition of the chocolate.
- PostInfrared surface pasteurization of packaged food products(2014) Linde, Mia; Chalmers tekniska högskola / Institutionen för kemi- och bioteknik; Chalmers University of Technology / Department of Chemical and Biological Engineering
- PostInvestigation of interactions between nanobodies and their antigens using SPR detection methods(2014) Mariotti, Michele; Chalmers tekniska högskola / Institutionen för kemi- och bioteknik; Chalmers University of Technology / Department of Chemical and Biological EngineeringNanobodies, or single domain antibodies, have gained a lot of attention recently in nanoscience because of their attractive properties such as small size, high stability, high flexibility, hydophilicity and ease of manufacture, which make them ideal candidates for a lot of application areas, including biotechnology, therapeutics and diagnostics. The aim of this Master Thesis is to evaluate the interactions between nanobodies and their binding partners by Surface Plasmon Resonance techniques. The goal of the first part of the thesis is to overexpress, purify and characterize three different proteins: His-eGFP, GFP and nanobody. The results indicated a succesfull overexpression and purification of His-eGPP and GFP, with a high level of purity achieved for both proteins. Nanobody was overexpressed but its purification led to many challenges, as the final purified protein had a very low density. The second part of the thesis investigates the experiments aimed at evaluating the interactions between a nanobody against GFP and a GFP protein, previously purified, on two biosensor surfaces: a Ni:NTA chip and an anti-his antibody immobilized on a CM5 chip. Furthermore, the interaction of a single nanobody on the two surfaces is compared with His-eGFP interaction on both surfaces. Results showed that the interaction between nanobodies and their binding partner can be investigated by SPR. In particular, nanobody showed a higher affinity for both biosensor surfaces compared to His-eGFP. Kinetics measurements indicated higher association rate constants and lower dissociation rate constants for nanobody binding to the anti-his-antibody surface compared to His-eGFP binding to same surface, confirming the high affinity of the nanobody for the anti-his-antibody surface. Results of the experiments involving the interaction between GFP binding to nanobody immobilized on the two surfaces indicated a very similar affinity at equilibrium of GFP for the immobilized Nb on both surface. On the other hand, kinetics measurements showed that GFP had a higher affinity for nanobody immobilized on the anti-his surface, as slower dissociation rate constants and slightly higher association rate values were obtained. In conclusion, the interaction between nanobody and its antigen was succesfully characterized and evaluated by SPR, but care must be taken while choosing the experimental parameters in order to minimize mass transport problems typical of SPR experiments.
- PostInvestigation of ultra high pressure size exclusion columns and chromatographic parameters for polymer characterization(2015) Västernäs, Amanda; Chalmers tekniska högskola / Institutionen för kemi och kemiteknik; Chalmers University of Technology / Department of Chemistry and Chemical Engineering