The brewing industry has considerable economic impact worldwide; therefore, demand exists for a better understanding of the organisms that cause beer-spoilage. Low nutrient levels, depleted oxygen levels, high alcohol levels, and the presence of antimicrobial hop compounds all play a role in making beer an inhospitable environment for most microorganisms. Nonetheless, there are bacteria that are resistant to all of these selective pressures. The most common beer-spoilage bacteria are the Gram-positive lactic acid bacteria <i>Lactobacillus</i> and <i>Pediococcus</i>. It is currently believed that hop-resistance is the key factor(s) permitting <i>Lactobacillus</i> and <i>Pediococcus</i> bacteria to grow in beer. However, it is likely that in addition, ethanol-tolerance and the ability to acquire nutrients also play roles in the beer-spoilage ability of <i>Lactobacillus</i> and <i>Pediococcus</i> isolates. The ability of <i>Lactobacillus</i> and <i>Pediococcus</i> to grow in beer was assessed and correlated to the presence of previously described beer-spoilage related genes, as well as with the presence of novel genes identified in this study. Molecular and culture-based techniques for detection and differentiation between <i>Lactobacillus</i> and <i>Pediococcus</i> isolates that can and cannot grow in beer were established and described in detail. Interestingly, beer-spoilage related proteins were often found to share homology with multi-drug transporters. As such, the presence of these beer-spoilage associated genes was also compared to the ability of isolates to grow in the presence of a variety of antibiotics and, unexpectedly, beer-spoiling bacteria were found to be more susceptible to antibiotics than were non beer-spoiling isolates of the same genus. Additionally, it was found that isolates of <i>Lactobacillus</i> and <i>Pediococcus</i> that can grow in beer do not group phylogenetically. In order to fully appreciate the relationship of speciation with beer-spoilage, phylogenetic and whole genome/proteome studies were conducted to clarify the taxonomy of the <i>Lactobacillus</i> and <i>Pediococcus</i> genera. Through the research in this thesis, a greater understanding of the mechanism(s) enabling bacteria to grow in beer has been gained and taxonomy of the genera <i>Lactobacillus</i> and <i>Pediococcus</i> has been clarified.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:SSU.etd-09032009-175224 |
| Date | 16 September 2009 |
| Creators | Haakensen, Monique Chantelle |
| Contributors | Korber, Darren, Qureshi, Mabood, Qualtiere, Lou, Phister, Trevor, Ziola, Barry, Deneer, Harry, Kusalik, Tony |
| Publisher | University of Saskatchewan |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://library.usask.ca/theses/available/etd-09032009-175224/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Saskatchewan or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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