Yegin, Yagmur (2020-11). Mechanistic Investigation of Inactivating Bacterial Food Pathogens with Nanoparticles. Doctoral Dissertation. Thesis uri icon


  • This research aimed to investigate the inactivation of foodborne pathogens with essential oil containing nanoparticles. Foodborne microbial pathogens continue to impose significant public health and financial burden in the U.S. despite the advent of numerous food processing technologies and food safety oversight systems designed to prevent pathogen transmission to consumers. Antimicrobial nanoparticles (NPs) were synthesized with geraniol essential oil component using the triblock copolymer Pluronic(R) F-127. Physico-chemical properties and antimicrobial effects were tested. Different sizes of NPs from 26 to 412 nm were obtained by adjusting concentrations of Pluronic(R) F-127 and geraniol. NPs displayed sustained release with a time constant of 24 hr. NPs showed better stability at neutral pH and room temperature compared to their stability at acidic and alkaline pH conditions (pH 4.0, 10.0) and decreased and elevated temperatures (4, 37, 50 ?C). Antimicrobial NPs inhibited S. Typhimurium and E. coli O157:H7 growth at 0.4 and 0.2 wt.%, respectively. Nanoencapsulation of geraniol enhanced antimicrobial activity of geraniol by lowering the required amount of essential oil component (EOC) for inhibition through improved transport of EOC to pathogen membranes. The interactions between Salmonella Typhimurium, Escherichia coli O157:H7, Listeria innocua, and Staphylococcus aureus and geraniol-loaded polymeric nanoparticles/nonencapsulated geraniol were investigated to gain new insight into their mechanisms of action against bacteria cells. Bacteria cells were treated with different concentrations of geraniol-loaded polymeric nanoparticles and non-encapsulated geraniol. Zeta (?) potential of bacteria cells increased from negative towards less negative in an antimicrobial concentration-dependent increase due to adsorption of cationic amine groups onto the negatively charged surface lipids. After the bacteria cells were treated with antimicrobial, cell membrane was disrupted and caused the death of the cells. Non-encapsulated geraniol also caused the aggregation of the cells and increased mean size value. Nanoencapsulation of geraniol enhanced its interaction with bacteria cells and increased its adsorption into internal compartments of the cells resulting breaking of the cells. Size measurements for NP-treated cells also showed that the size of the cells was smaller than untreated cells. Based on the present work it has been reported that 1) the use of antimicrobial nanoparticles can significantly increase the efficiency of encapsulated essential oil components by penetrating cell membrane, 2) encapsulated geraniol shows significantly better efficacy against pathogenic bacteria than non-encapsulated geraniol, 3) greater alteration on the surface charges of the cells were measured for the NP-treatment having stronger antimicrobial properties than free geraniol-treatment, 4) mean size value decreased for NP-treated bacteria cells due to break down of the cells while mean size value increased for non-encapsulated geraniol-treated cells due to aggregation of the cells. Overall, results of this research will be utilized to provide helpful information to the food industry for a better understanding of inactivating bacterial food pathogens with nanoparticles.

publication date

  • November 2020