Gillis, AnnikaMartin, LauraLauraMartin2025-07-012025-07-012025-06-0920252025-06-09https://hdl.handle.net/2078.2/43279In the food industry, the persistence presence of B. cereus group members raises public health concerns throughout the production chain. Thus, the efficient management of these bacteria is essential to mitigate public health risks. In this view, phages, which specifically infect bacteria, and phage-based solutions have shown promise as novel methods of control, but further investigations are necessary to determine their potential applications in agro-industrial fields. This study aims to deepen the understanding and explore potential applications of phages in controlling members of the B. cereus group members within the context of food safety. Three phages, Alexis, Helenis and Lasnis, were evaluated for their stability under various environmental conditions and for their antibacterial efficacy in laboratory media, with Helenis additionally assessed for its antibacterial activity in milk. The outcomes of this study showed, first, that phages Alexis, Helenis, and Lasnis exhibited notable tolerance to a broad range of NaCl concentrations. Helenis and Alexis sustained high titers exceeding 10⁸ PFU/mL even at 3000 mM NaCl, an important feature for application in diverse food matrices. Although Lasnis did not reach this benchmark, it maintained a viable titer under high-salt conditions. Besides, none of the three phages required the addition of divalent ions such as Ca²⁺ or Mg²⁺ to preserve infectivity or adsorption efficiency, which simplifies their formulation for industrial use. Then, in terms of antibacterial activity, Alexis and Helenis exhibited strong lytic effects against B. thuringiensis GSX002, with inhibition enhanced at higher MOI, allowing dose flexibility depending on the application. Lasnis showed reduced efficacy against B. thuringiensis GSX002, with bacterial regrowth observed, compared to Alexis and Helenis. Finally, Helenis also reduced the growth of the emetic B. cereus IS075 in milk at 20 °C, highlighting its potential as a biocontrol agent in real food matrices. Further characterization is necessary to confirm their full potential and optimize its use in food safety applications. Overall, this work indicates the potential of phage candidates, Helenis, Alexis, and Lasnis, as potential biocontrol tools that can be used from farm to fork. These phages exhibited promising characteristics and limitations underscores the need for further studies. More investigations are needed on resistance mechanisms, along with further genomic characterization and validation under industry-relevant conditions to be used as biocontrol agents in the food industry.Bacillus cereusBacteriophagesFood safetyPhage therapyBiocontroltext::thesis::master thesis