Examensarbeten för masterexamen // Master Theses
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- PostDevelopment of a growth-sensitive malonyl-CoA platform strain(2019) Hedin, Alex; Chalmers tekniska högskola / Institutionen för biologi och bioteknik; Chalmers University of Technology / Department of Biology and Biological EngineeringThe transition from a fossil reliance society towards full reliance on sustainable alternatives is a difficult challenge. The development of high-performant microbial cell factories, which efficiency convert renewable carbon sources to generate industrially relevant compounds, are to date not economically compatible with the current less sustainable alternatives. Through metabolic reprogramming, the production of compounds at industrial levels could be obtained by increasing cofactors and substrates levels. In this thesis, we developed a growth-sensitive malonyl-CoA platform strain, able to select for an enrichment of the highly relevant precursor, malonyl-CoA. Through coupling it with a CRISPR-dCas9 gRNA library we performed a biosensor assisted laboratory evolution (BALE). Three targets, previously described to significantly increase the downstream product of malonylCoA, 3-Hydroxypropionic acid, were selected after 24 hours and more targets will be characterized.
- PostEvaluation of pre-concentration techniques for gas chromatographic determination of low amounts of volatile contaminants and degradation products(2018) Nylander, Erik; Chalmers tekniska högskola / Institutionen för biologi och bioteknik; Chalmers University of Technology / Department of Biology and Biological EngineeringThe project investigated the compared two pre-concentration methods, Thermal Desorption System (TDS) coupled to a Thermal Extractor (TE) and Multiple Headspace Injection (MHI) using a Multiple Purpose Sampler (MPS) for detecting volatile amines in solid pharmaceutical products and synthesis precursor chemicals samples. The TDS-TE and MHI extractions are directly injected into a Cold Injection System (CIS). The CIS captures the analytes using cold temperatures to condense the vapours. The sample is then injected into a gas chromatograph-mass spectrometer system. The resulting mass spectrum extracted from the chromatogram can then be used in coordination with a mass spectral library with search program to identify amines present in the samples. The two pre-concentration methods were compared based on sensitivity to detect odorous amines, overall analyses time and general ease of use. The TE-TDS method was more labour intensive and required longer analyses times but resulted in higher sensitivity, ability to detect most amines and ability to adapt to smaller sample sizes and lower concentrations in the sample. MHI by contrast is easier to use as the MPS is largely automated and faster but the sensitivity might not be sufficient for detecting volatile amines in solid pharmaceutical products. The TDS-TE method is preferable due to greater sensitivity, and further work should be done to increase the automation of this pre-concentration method.
- PostMetabolic Engineering of S. cerevisiae for Production of a Flavour and Fragrance Compound(2018) tolgo, Monika; Chalmers tekniska högskola / Institutionen för biologi och bioteknik; Chalmers University of Technology / Department of Biology and Biological EngineeringThe market of flavours and fragrances in 2016 was estimated to be around 30 billion USD. Due to several reasons, of which the main one is consumers’ growing interest in natural products, the industry has been turning to more sustainable and natural methods such as biotechnology. The aim of this Master’s thesis was to metabolically engineer the fatty acid metabolism of S. cerevisiae for production of a high-value flavour and fragrance compound X using a novel pathway. For this, several enzymes from various organisms belonging to the same enzyme class were screened. Two different background strains were tested from which one most probably produced the compound of interest but in concentrations too low to be detected by the undeveloped capturing and extraction method for compound X. Using a different extraction method, on the other hand, a close precursor Y was detected. Several different fatty acid feedings were also tested in order to increase the production of compounds X and Y but did not seem to have the expected effect. On the other hand, it was shown that one specific fatty acid suitable as an ideal precursor for compound X was taken up intracellularly, even though it did not cause an increase in the precursor Y.
- PostStorage stability of the dried seaweed species Ulva lactuca and Porphyra umbilicalis subjected to different pre-treatments prior to drying(2018) Liberg Krook, Johanna; Chalmers tekniska högskola / Institutionen för biologi och bioteknik; Chalmers University of Technology / Department of Biology and Biological EngineeringSeaweeds has large potential as a promising biomass, not least in the production of food and food ingredients. In order to have a large-scale production of seaweed-based ingredients and products, cost effective and functioning preservation and storage solutions have to be developed. The production and utilization of seaweed in Sweden is under development and in the Sweaweed project, techniques for cultivation of seaweed species Ulva lactuca and Porphyra umbilicalis are developed and the use of the species for high value products evaluated. In this master thesis project, the storage stability of oven dried Ulva lactuca and Porphyra umbilicalis subjected to different pre-treatments was investigated. To evaluate the storage stability, ascorbic acid content, formation of lipid oxidation products and colour was monitored during a period of 230 days. Additionally, the crude composition was analyzed. Prior to drying the seaweed had been either coated with whey coating or soaked in freshwater. Subsequent storage was performed in either light or darkness in ambient temperature. To evaluate the effect of oven drying per se, samples where freeze dried without any pretreatment and stored under the same conditions. Throughout the storage study there was a loss of ascorbic acid in all samples. Porphyra samples had a higher initial ascorbic acid content than Ulva samples but exhibited a greater loss throughout the storage. Storage under light conditions to some extent increased the loss of ascorbic acid in both Ulva and Porphyra. Coated samples had initially lower ascorbic acid content than non-coated samples but lost less ascorbic acid during storage.Lipid oxidation was analyzed as formation of free aldehydes; malondialdehyde!(MDA), 47hydroxy727hexenal (HHE) and 47hydroxy727nonenal!(HNE). All three aldehydes were detected in all samples in the order of magnitude MDA>HHE>HNE. Light storage increased the formation of aldehydes in oth lva nd Porphyra and after 230 days lowest levels were found in samples stored in darkness. Freeze dried Ulva and Porphyra had higher concentrations of MDA, HHE and HNE than oven dried samples, and were subjected to the largest aldehyde increase in light storage. During storage, samples also lost their green and yellow pigments, especially in light storage, which was visible to the eye especially for freeze dried samples. Overall, the whey coating did not seem to protect the seaweed during drying or storage and freeze drying was not better than oven drying at 40°C in preserving nutritional value based on the parameters analyzed.