Date

2023-1-20

Author

Tidim, Gökçe

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In recent years, there has been intense research going on to develop new packaging technologies to improve the safety and quality of the food. Natural polymers not only reduce the consumer health risks but also provide less processed and more environment friendly food packages. Alginate and chitosan are suitable polymers for food technology due to their biocompatibility, biodegradability, and non-toxicity. In addition to the antibacterial properties of chitosan, pH responsive behaviour of alginate and chitosan makes them promising materials for encapsulation and controlled release of functional molecules from surfaces. On the other hand, due to intensive usage of antibiotic drugs, scientists are in the search of substitute strategies. Bacteriophages are strong candidates for this purpose due to being natural predators of bacteria. In this thesis study, multilayer films of alginate (ALG) and Chitosan (CHI) were prepared through layer-by-layer (LbL) self-assembly technique. Multilayers were characterized with respect to physicochemical properties such as growth profile, stability, and surface morphology. The drying process between each layer deposition during LbL assembly was found to be critical on the multilayer growth profile. Multilayers which were dried only at the end of LbL process showed exponential growth profile, whereas CHI/ALG multilayers which were prepared by applying a drying procedure after each layer deposition displayed linear growth profile. Multilayers which were not exposed to drying process between the layer depositions were preferred for phage loading studies due to higher film thickness, rough surface morphology, and practicality in preparation. Multilayers were found to be stable at both acidic and neutral pH conditions. The roughness of multilayers increased remarkably as the layer number increased. Bacteriophages, termed T4, which show infection activity towards Salmonella enterica subsp. enterica serovar Enteritidis were loaded into the films. The effects of layer number, loading pH and release pH on the antibacterial activity of bacteriophage loaded multilayers have been investigated. The pH at which phages were incorporated into multilayers was also found to be critical on the antibacterial activity of the multilayers. Zone formation was observed when phages were loaded at pH 7.0. In contrast, a clear zone was not formed when phages were incorporated at pH 5.0. The pH was also critical on the antibacterial activity. Phage loaded CHI/ALG multilayers demonstrated antibacterial activity at neutral pH. However, zone formation was not observed at moderately acidic pH conditions. Finally, several antibacterial agents such as curcumin, thymol, lactic acid, and tannic acid were loaded into ALG/CHI LbL films, and their antibacterial properties were compared with those of phage loaded multilayers . No zone formation was obtained from disc-diffusion tests with the films containing antibacterial agents, pointing out the efficacy of bacteriophages as promising antibacterial entities.

Subject Keywords

Layer-by-layer, Natural biopolymers, Bacteriophage, Food packaging, Antibacterial

URI

https://hdl.handle.net/11511/102026

Collections

Graduate School of Natural and Applied Sciences, Thesis