magistrsko delo
Ela Stergar (Author), Polona Jamnik (Reviewer), Neža Čadež (Mentor), Miha Tome (Co-mentor)

Abstract

Za izboljšave industrijskih sevov mikroorganizmov v živilski industriji uporabljamo različne ne-rekombinantne tehnike, kot sta mutageneza in usmerjena evolucija. Pri tem v poliploidnih sevih kvasovk pride do alelne variabilnosti in s tem do bojazni, da se bodo pozitivne mutacije izgubile s popravo s homologno rekombinacijo. Temu se lahko izognemo s sporulacijo izboljšanih mutant, ob čemer pride do haploidnega stanja spore, ki po avto-diploidizaciji izgubi alelno variabilnost. Pri tem moramo biti pazljivi, da smo obdržali želeni fenotip sporuliranih mutant. Namen magistrskega dela je bil preveriti, ali so eno-sporne kvasovke ohranile spremenjen fenotip privzema maltoze. Sporulacijo smo dosegli tako, da smo kvasovkam omejili hranila in odvzeli vir dušika. Gojili smo jih na bogatem gojišču YPD in nato na gojišču z acetatom brez vira dušika. Za razgradnjo celične stene aska smo uporabili tetradni sok z litikazo, sproščene askospore smo nato ločili z mikromanipulatorjem. Eno-spornim kulturam smo določili sposobnost fermentacije maltoze v 2-mL mikrocentrifugirkah in izbranim kulturam tudi v 50-mL centrifugirkah. Kinetiko porabe sladkorjev in tvorbo etanola med fermentacijo smo določili z analizo HPLC. Ugotovili smo, da so nekatere eno-sporne kulture ohranile spremenjeni fenotip privzema sladkorjev v večjem merilu. V zadnjem delu naloge smo na podlagi dolžine pomnožka PCR lokusa MAT določili paritveni tip eno-spornih kultur, ki nam je pokazal, da so bile kvasovke po sporulaciji v večini ponovno diploidne.

Keywords

kvasovke;Saccharomyces cerevisiae;varjenje piva;poraba sladkorjev;maltoza;katabolna represija;sporulacija;

Data

Language: Slovenian
Year of publishing:
Typology: 2.09 - Master's Thesis
Organization: UL BF - Biotechnical Faculty
Publisher: [E. Stergar]
UDC: 602.3:582.282.23:663.45
COBISS: 167599875 Link will open in a new window
Views: 16
Downloads: 7
Average score: 0 (0 votes)
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Other data

Secondary language: English
Secondary title: Fermentation capacity of monospore beer yeast mutants with improved maltose utilisation
Secondary abstract: Mutagenesis and directed evolution are non-recombinant techniques used to improve industrial strains of microorganisms in the food industry. In polyploid yeast strains, allelic variability occurs, which causes concerns that positive mutations will be lost through repair by homologous recombination. This can be avoided by sporulating the improved mutants, resulting in a haploid spore state that loses allelic variability after auto-diploidization. In doing so, we must be careful to maintain the desired phenotype in the sporulated mutants. The aim of the master 's thesis was to determine whether monosporic yeasts have preserved the altered maltose uptake phenotype. Sporulation was achieved by restricting the nutrients in the yeast cultivation medium by removing the nitrogen source. The yeasts were first, grown on nutrient-rich medium and then they were transferred onto acetate medium lacking nitrogen source, where they formed ascospores. To degradate their cell wall, we prepared tetrad juice with lyticase and separated the released ascospores with a micromanipulator. We determined the ability of monosporic cultures to ferment maltose in 2-mL microtubes and selected cultures also in 50-mL tubes. The kinetics of sugar consumption and ethanol formation during fermentation were determined by HPLC analysis. We found that some monosporic cultures retained the altered sugar uptake phenotype also in large scale. In the last part of the work, we determined the mating type based on the length of the PCR amplified MAT locus of monosporic cultures, which showed that most of the monosporic yeast cultures were auto-diploidized.
Secondary keywords: yeasts;Saccharomyces cerevisiae;beer brewing;sugar assimilation;maltose;catabolite repression;sporulation;
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: 1 spletni vir (1 datoteka PDF (XI, 56 str., [5] f. pril.))
ID: 20086262