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Development of contamination resistance strategies for bioindustrial applications Open Access


Other title
saccharomyces cerevisaie
lactic acid bacteria
Type of item
Degree grantor
University of Alberta
Author or creator
Dul, Erin L
Supervisor and department
Bressler, David (Agricultural, Food, and Nutritional Science)
Examining committee member and department
Sauvageau, Dominic (Chemical Engineering)
McCormick, John (Microbiology and Immunology, University of Western Ontario)
Gaenzle, Michael (Agricultural, Food, and Nutritional Science)
McMullen, Lynn (Agricultural, Food, and Nutritional Science)
Department of Agricultural, Food, and Nutritional Science
Bioresource Technology
Date accepted
Graduation date
Doctor of Philosophy
Degree level
Contamination by lactic acid bacteria is a major source of inefficiency in the bioethanol industry. Contaminated fermentations exhibit lowered ethanol yields and contamination events often require shutdown of the entire process for cleaning and decontamination. The first objective of this study was to develop fermentation yeast that secrete bacteriocins, proteins that kill lactic acid bacteria, to counteract this contamination. A strain that secretes leucocin A was successfully developed; however, the strain did not exhibit secretion levels that were industrially relevant. Two reasons for poor secretion: the interaction of the bacteriocin with the cell membrane and the prevention of diffusion by the cell wall, were established. The second objective of this study was to produce the circular bacteriocin, carnocyclin A, heterologous in E. coli, with the ultimate goal of producing industrial levels of the bacteriocin for use in the food and biorefining industries. The bacteriocin was produced but was not cyclized at detectable levels. The third objective of the study was to screen for additive and synergistic properties of antimicrobials used in the bioethanol industry against lactic acid bacteria isolated from industrial ethanol production facilities. The antimicrobials screened included a conventional antibiotic, a hop compound, and two bacteriocins. The antimicrobials exhibited additive properties, with leucocin A potentially showing synergistic properties with other inhibitors including nisin. The development of new biological fermentation pathways for yeast, as well as engineering yeast to produce proteins like bacteriocins, could be expedited by improving cloning processes. The fourth objective of this study was to develop a ligation independent cloning methodology to improve the workflow of the cloning process and the percentage of positive clones produced. This methodology had similar percentage positive clones to other cloning processes.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
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