Bio characters of lactic acid bacteria from retail yoghurt in Singapore

There are various foodborne bacteria-causing disease outbreaks such as Salmonella, Campylobacter, Listeria monocytogenes, Vibrio cholerae etc, Cases such as Salmonella mostly from raw food or poultry have occurred recently in Singapore and has taken a toll in Singapore hence consumers became more concern with the safety of imported food as we become vulnerable to the increasing trend of foodborne illnesses. The purpose of this study is to test on the antimicrobial properties of Lactobacillus casei and Streptococcus thermophilus bacteria found in yoghurt against food pathogens. The antimicrobial properties of these Gram-positive bacteria were further demonstrated by its ability to hinder growth of pathogenic bacteria in the human gut. The research work first involves isolating the lactic acid bacteria (LAB) from retail yoghurt and then confirming their genus from a pure isolate using Polymerase Chain Reaction (PCR) then Sanger Sequencing by the 16S rRNA - a genetic marker for bacterial study. Agar diffusion method is by obtaining the properties secreted by the LAB bacteria from liquid culture and will be tested against pathogens to observe its capacity for growth inhibition. Most of the isolates show presence of antimicrobial properties as they hinder growth of the pathogen in a way comparable to their sensitivity towards antibiotics such as ampicillin. In future, the result of the study on antimicrobial properties of these bacteria could work on fighting extended spectrum beta-lactamases (ESBLs) of Escherichia coli or Klelsiella which are becoming the main concern in the healthcare sector.Bachelor of Engineering (Chemical and Biomolecular Engineering