Examensarbeten för kandidatexamen // Bachelor Theses
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- PostCRISPR/Cas9 för introduktion av metaboliska vägar som möjliggör konsumtion av ättiksyra och xylos i Saccharomyces cerevisiae(2019) Björck, Henrik; Blick, Elin; Fredríksson, Johanna; Hammer úr Skúoy, Pauline; Ytterberg, Karin; Dehlén, Linnéa; Chalmers tekniska högskola / Institutionen för biologi och bioteknik; Chalmers University of Technology / Department of Biology and Biological EngineeringAbstract CRISPR/Cas9 for introduction of metabolic pathways to enable the consumption of acetic acid and xylose in Saccharomyces cerevisiae An alternative to fossil fuel is the usage of Saccharomyces cerevisiae in the process of producing bioethanol from lignocellulosic biomass. However, S. cerevisiae can only utilise around 70% of the sugars from lignocellulose to produce ethanol, rendering the process inefficient. In order to increase the use of the sugars present in lignocellulosic biomass, this study aimed to introduce metabolic pathways for both acetic acid and xylose consumption in S. cerevisiae and analyse the effects of the modifications. For the acetic acid consumption the adhE-gene was introduced whereas for the xylose consumption three genes were introduced encoding xylose reductase (XR), xylitole dehydrogenase (XDH), and xylulokinase (XK). The CRISPR/Cas9 genome editing system was transformed into the cells to introduce the two metabolic pathways seperately in 12 strains of S. cerevisiae. The 12 strains included both laboratory strains as well as industrial and wild type strains. To analyse the results the three methods colony PCR, growth on solid selective media, and growth on liquid selective media were used. All studied strains had successful transformations for both pathways. On the other hand, the number of colonies varied between the different strains. For both pathways, the laboratory strains generally had more transformed colonies than the industrial and wild type strains. The lack of an integrated selection marker when using CRISPR/Cas9 as the genome editing tool made the selection of successfully engineered strains difficult. However, the results from growth in liquid media and colony PCR indicated that the integration of the metabolic pathway was successful for some of the strains. These results show that CRISPR/Cas9 is an useful method for integrating new metabolic pathways in S. cerevisiae and with further investigations the strains could provide important information in the development of bioethanol production.
- PostEtanolbildande acetogener för syngasfermentering –en jämförande studie(2018) Mårtenson, Sara; Stavås, Emma; Hadi, Fahim; Landström, Carl-Johan; Frithiofson, Emil; Chalmers tekniska högskola / Institutionen för biologi och bioteknik; Chalmers University of Technology / Department of Biology and Biological EngineeringThe use of fossil fuels contributes to global warming, which is one of the biggest pro-blems in today’s society. An alternative to reduce the use of fossil fuels is to instead use renewable fuels, such as bioethanol. One way to produce bioethanol is to allow anaerobic microorganisms to ferment syngas, a mixture of carbon monoxide, carbon dioxide and hydrogen gas. The purpose of the work was to evaluate and rank microorganisms, which by fermentation of syngas, have the greatest potential for high ethanol production. A literature review gathered information of around 100 microorganisms to find the orga-nisms with the greatest potential for ethanol production. The results showed that Clostri-dium autoethanogenum, Clostridium carboxidivorans, Clostridium coskatii, Clostridium ljungdahlii and Clostridium ragsdalei were the microorganisms with the greatest poten-tial. In addition to the literature study, an experiment was performed where inhibitor tolerance was examined. The inhibitor ammonia was added to C. ljungdahlii, C. autoethanogenum and C. carboxidivorans. These three organisms were deemed to have high potential in the literature review and were available at the institution. The result showed that no organism grew at 100 mM of ammonia. C. ljungdahlii showed the highest tolerance as neither ethanol formation nor growth decreased significantly at 50 mM and below. The ethanol production of C. autoethanogenum decreased already at 35 mM. The ethanol production C. carboxidivorans decreased at 50 mM ammonia. The work was carried out at Chalmers University of Technology.
- PostNew products from seafood side streams to stimulate a circular economy(2019) Haldén, Cecilia; Lidfeldt, Matilda; Haxhijaj, Drilon; Jiresten, Erik; Johansson, Sofia; Björkner, Malin; Chalmers tekniska högskola / Institutionen för biologi och bioteknik; Chalmers University of Technology / Department of Biology and Biological EngineeringThe Paris Agreement implicates that society will take necessary action to prevent the global mean temperature to rise more than 1.5°C. Since 80% of greenhouse gas emissions from agriculture originate from livestock, a protein shift is needed. This project has investigated the possibilities to implement proteins recovered from solid and liquid seafood processing side streams in different types of food products including fish ball, fish sausage, fish soup and mayonnaise. The proteins were recovered from fish processing by-products using the pH-shift method and shrimp processing water using flocculation. Effect of using the alternative proteins on proximate composition (protein, moisture, fat and mineral content), color, texture and sensorial properties of the products were evaluated. The fish soups were found as the least promising products, due to the low protein content and low scores in the sensory analysis. The results showed that 50% substitution of salmon protein isolate in fish balls and fish sausages with fish mince had no negative impact on the products quality but problems with a complete replacement may arise, especially regarding texture and color of the products. The mayonnaises containing both fish and shrimp proteins showed promising properties compared to the samples with egg protein. It was concluded that more studies of products with isolate are needed. Taste tests, different ratios, of mince and isolate, and repeats of already performed tests and products would provide useful future knowledge.
- PostVärmestabila enzym från svampen Scytalidium thermophilum(2017) Bergklint, Sofia; Bergman, Sebastian; Larsson, Elise; Nydahl, Karin; Persson, Frida; Åström, Marianne; Chalmers tekniska högskola / Institutionen för biologi och bioteknik; Chalmers University of Technology / Department of Biology and Biological EngineeringDe miljöproblem som världen idag står inför beror till stor del på förbränning av fossila råvaror. En av de största utmaningarna för att minska den negativa miljöpåverkan är att hitta sätt att använda förnybart kol, till exempel i form av växtbiomassa, istället för fossilt. I detta kandidatarbete, som genomförts på Chalmers tekniska högskola år 2017, har den sedan tidigare okända stammen FCH 6.2 av den termofila filamentösa svampen Scytalidium thermophilum undersökts som källa till enzym för omvandling av växtbiomassa. Målet med projektet var att hitta så effektiva och värmestabila enzym som möjligt. Därför har svampen odlats på flera olika odlingssubstrat (kolkällor), samt enligt två olika odlingsmetoder, flytande kultur och en kultur där endast en liten mängd vätska tillsätts till kolkällan. Målet var sedan att jämföra resultaten mellan olika odlingar för att se vilken kolkälla och odlingsmetod som genererat mest enzym med så hög enzymatisk aktivitet som möjligt. För att kunna jämföra de olika odlingarna mättes proteinkoncentrationen i extraktionslösningarna. Därefter jämfördes enzymens aktivitet på både naturliga polysackarider och syntetiska enzymsubstrat. Resultatet visade att S. thermophilum producerade värmetåliga enzym som hade aktivitet vid både 60° C och 70° C. Därav kan enzym producerade av S. thermophilum FCH 6.2 vara av intresse för användning inom industrier. Mer forskning skulle kunna visa vilka enzym som produceras vid odling på olika kolkällor. Vidare vore det intressant att jämföra enzymen med kommersiella enzymblandningar för att få en uppfattning om enzymens effektivitet.