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Antimicrobial properties of lactic acid bacteria isolated from fermented foods and drink

Tyson, Kathryn (2020) Antimicrobial properties of lactic acid bacteria isolated from fermented foods and drink. Masters by Research thesis (MSc), Manchester Metropolitan University. MSc by Research.


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Lactic acid bacteria isolated from fermented food have shown to be antimicrobial in activity towards known pathogens. As resistance to standard antibiotics becomes more prevalent, there is always the need to discover new sources of effective antimicrobials. There have been numerous studies on identifying lactic acid bacteria and in most cases, the bacterocin has been extracted and used to test against the known pathogens. In this study, bacteria were isolated from fermented foods such as sour beer, kefir and kombucha using selective agars. These were then identified using the Gram stain method and API kits. The isolation procedure had limited results and only a few bacteria were isolated and identified. These were: Lactobacillus Plantarum (73.4% likelihood) and Pediococcus acidilactici (99.9% likelihood) from sour beer and Lactococcus lactis (83.15% likelihood) from kefir. The identified organisms were tested for antimicrobial activity using the disc method on agar and the pathogen Escherichia coli. Lactococcus lactis isolated from kefir was found to possibly exhibit antimicrobial activity. This was then tested against other pathogens such as Salmonella Spp and Staphylococcus aureus. The isolate of Lactococcus lactis was shown, to have some possible antimicrobial activity against Salmonella Spp and Staphylococcus aureus.

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