Putative antibacterial activity of lactic acid bacteria isolated from local goat milk / Nur Shahdina Hani Mohd Zaki

Nur Shahdina Hani , Mohd Zaki (2022) Putative antibacterial activity of lactic acid bacteria isolated from local goat milk / Nur Shahdina Hani Mohd Zaki. Masters thesis, Universiti Malaya.

	PDF (The Candidate's Agreement) Restricted to Repository staff only Download (232Kb)
	PDF (Thesis M.A.) Download (753Kb)

Abstract

Antimicrobial compounds excreted by microorganisms have attracted lots of attention among researchers in the field of food microbiology as an alternative for natural preservatives and antibiotics. To compete for nutrients and space in a particular habitat, bacteria often produce natural antimicrobial compounds such as organic acids, antifungal, siderophores and bacteriocins. Hence, the aim of this study is to identify the bioactive antimicrobial compounds deriving from lactic acid bacteria (LAB) isolated from local goat milk. The screening of antimicrobial activity from 24 bacteria isolated from goat milk led to the isolation of Enterococcus faecium FGa, Enterococcus faecium RGB, Bacillus cereus FG1 and Serratia marcescens FG3. These strains show good inhibition zones against varying types of foodborne pathogens such as Staphylococcus aureus SA7001, Shigella boydii SB1003, Shigella dysenteriae SD1007 and Salmonella typhimurium SM4001. The antimicrobial substances in cell-free culture supernatant of all four isolates were stable against S. aureus at different temperatures, pH and also when exposed to proteolytic enzymes except pepsin for E. faecium FGa and E. faecium RGB. The mode of action for isolates was determined as bactericidal where they lysed the cells of S. aureus which induced the unbalanced growth of its cell cycle. Since LAB are our main aim, both E. faecium FGa and RGB have undergone further safety evaluation. Both strains show good probiotic properties since they can survive well under conditions simulating the human GI tract and do not show any potential virulence characteristics. Enterocin A has been detected through PCR amplification in one of our E. faecium strains which is E. faecium FGa. This indicates it as one of the possible compounds that is responsible for antimicrobial activity. E. faecium FGa has also undergone Q-TOF LC/MS analysis and several metabolites that may also contribute to antimicrobial activity have been detected which are netilmicin, maleic acid and 2-furonic acid. Hence, E. faecium FGa can be used as a potential bio-preservative or protective culture in our food industry.

Actions (For repository staff only : Login required)