Discovery and evaluation of novel and characterised bacteriocins for future applications

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Egan, Kevin
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University College Cork
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Bacteriocins are a heterogeneous group of small, ribosomal-synthesised, antimicrobial peptides produced by bacteria, capable of inhibiting bacteria both closely related or indeed those from other genera than the producer. These peptides are often active in the nanomolar range making them highly potent in low concentrations. This thesis expands the large body of research and knowledge that exists in the field of bacteriocins. Firstly, a literature review examines the current and potential applications of bacteriocins to control spore-forming bacteria in food manufacturing. This review was the first to examine the mechanisms that underpin the anti-spore potential of bacteriocins and their viable use. A second literature review examined the efficacy of bacteriocin antibiotics as an alternative to current antibiotics and their lowered potential to induce microbiota dysbiosis during treatment. The first research chapter used conventional bacteriocin culture-based screening approaches in combination with whole genome in silico screening and peptide characterisation to discover new antimicrobial candidates in the genus Geobacillus. This resulted in the discovery of the potentially novel bacteriocin thermocin 458, who’s amino acid sequence and molecular mass is unknown due to an interesting inability to generate enough peptide for in depth physicochemical characterisation. The second research chapter sought to identify the full potential of the genus Geobacillus as a reservoir for novel bacteriocin candidates using a bioinformatic approach. This ultimately resulted in the discovery of many potential bacteriocin gene clusters across a variety of bacteriocin classes that will likely ignite further in vitro characterisation as a result. The third and final research chapter of this thesis sought to advance bacteriocin mutagenesis towards potential applications in cheese manufacture. Using a novel developmental approach, five new cheese starter cultures were created. Although three of the starter cultures produce nisin variants, they were created in a process that certifies their classification as non-genetically modified microorganisms (GMM) for contained use. This approach and its resultant non-GMM status is critical to future application and commercialisation of this technology. This thesis seeks to drive and generate interest in bacteriocin discovery and application in both academia and industry. Furthermore, the studies contained provide direction for future development within this field and demonstrate the efficacy of bacteriocin use in both food and medicine applications.
Bacteriocin , Antimicrobial , Antimicrobial peptides
Egan, K. 2018. Discovery and evaluation of novel and characterised bacteriocins for future applications. PhD Thesis, University College Cork.