magistrsko delo
Eva Pavliha (Author), Lorena Butinar (Reviewer), Neža Čadež (Mentor), Miha Tome (Co-mentor)

Abstract

V magistrski nalogi smo želeli prilagoditi lokalna izolata kvasovk Saccharomyces cerevisiae in Lachancea thermotolerans na pivovarsko okolje z metodo usmerjene evolucije. Namen poskusa je bila izboljšava sevov za fermentacijo pivine preko odprave katabolne represije z glukozo in izboljšanje privzema maltoze in maltotrioze. V prvem delu naloge smo optimizirali parametre mutageneze za obe kvasovki, na podlagi katerih smo potem izvedli mutagenezo z etilmetansulfonatom in z UV svetlobo. Sledilo je nacepljanje na trdno gojišča z inhibitorjem katabone poti glukoze, 2-deoksiglukozo, s katero smo ustvarili selekcijski pritisk. Z obema mutagenoma smo uspešno pridobili mutante, ki so bile odpornejše na inhibitor in so domnevno preferenčno sprejemale maltozo. Drugi del naloge je obsegal selekcijo mutant divjih sevov, potrjevanje njihovega spremenjenega fenotipa kinetike privzema glukoze in maltoze glede na divji sev med fermentacijo pivine, ter kemijsko analizo piv z visokotlačno tekočinsko kromatografijo. Pri ovrednotenju fermentativnih in tehnoloških lastnosti dobljenih mutant smo dobili mutante obeh vrst kvasovk, ki so bile odporne na inhibitor 2-deoksiglukozo, ter so s tem imele odstranjeno represijo z glukozo, in so zato hitreje privzemale maltozo.

Keywords

kvasovke;Saccharomyces cerevisiae;Lachancea thermotolerans;proizvodnja piva;fermentacija pivine;poraba sladkorjev;glukoza;maltoza;usmerjena evolucija;mutageneza;selekcijski pritisk;

Data

Language: Slovenian
Year of publishing:
Typology: 2.09 - Master's Thesis
Organization: UL BF - Biotechnical Faculty
Publisher: [E. Pavliha]
UDC: 663.45:579.25:582.282.23
COBISS: 114790659 Link will open in a new window
Views: 79
Downloads: 20
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Other data

Secondary language: English
Secondary title: Adaptation of yeast isolates from Vipava valley for wort fermentation with directed evolution
Secondary abstract: In this master thesis, we aimed to adapt local isolates of the yeasts Saccharomyces cerevisiae and Lachancea thermotolerans for wort fermentation using directed evolution. The aim of the experiment was to improve the yeasts by eliminating catabolite repression with glucose in order to improve the consumption of maltose and maltotriose. Firstly, we optimised the parameters of mutagenesis for both yeast isolates. Based on these results, we performed mutagenesis with two mutagens, ethyl methanesulfonate and UV light. Then we cultivated these yeasts on the solid growth medium with the inhibitor of glucose catabolic pathway, 2-deoxyglucose, with which we established selective pressure. With both mutagens we successfully obtained mutants that were more resistant to the inhibitor and which presumably had preference for maltose. The second part of the experiment involved the selection and confirmation of the changed phenotype regarding maltose consumption of the mutants during wort fermentations and the chemical analyses of the beer samples with the high-performance liquid chromatography. We succeeded to obtain mutants that showed resistance to the inhibitor 2-deoxyglucose, abolished repression with glucose, and therefore also utilized maltose faster than the wild strains.
Secondary keywords: yeasts;Saccharomyces cerevisiae;Lachancea thermotolerans;beer production;wort fermentation;carbohydrates;glucose;maltose;directed evolution;mutagenesis;selection pressure;
Type (COBISS): Master's thesis/paper
Study programme: 0
Embargo end date (OpenAIRE): 1970-01-01
Thesis comment: Univ. v Ljubljani, Biotehniška fak., Oddelek za mikrobiologijo
Pages: XII, 57 f., [20] f. pril.
ID: 15866058