Nur Huda Faujan [Supervisor]Ilyanie Binti Hj Yaacob2024-05-292024-05-292023-03Ilyanie Hj Yaacob. (2023). Characterization of Probiotic Lactic Acid Bacteria Isolated From Malaysian Fermented Food And Their Cholesterol Modulation Properties [Doctoral dissertation, Universiti Sains Islam Malaysia]. USIM Research Repository.https://oarep.usim.edu.my/handle/123456789/13181Matric: 4181231(FST)-Restricted Until 2026Hypercholesterolemia is associated with the development of various cardiovascular diseases. Maintenance of serum cholesterol levels can reduce the risk of getting the disease, including dietary intake containing probiotics that are able to modulate cholesterol homeostasis. The objective of this study was to isolate potential probiotic lactic acid bacteria (LAB) strains from Malaysian fermented foods and to evaluate their potential cholesterol-modulating activities. The physicochemical and colourimetric characteristics of all samples varied depending on the ingredients and fermentation procedures. Initially, 59 LAB isolates were successfully isolated from the products. A series of experiments were performed to evaluate the probiotic characteristics of each isolate. Out of 59, 17 isolates demonstrated tolerance to pH3 with survival rates above 90%. Further analysis performed on these isolates demonstrated their abilities to survive in 0.3% bile salt environments and inhibit the growth of selected foodborne pathogens to varying degrees (5.50 mm to 14.17 mm). All strains also did not show undesirable β-haemolytic activities, as well as were susceptible to ampicillin and chloramphenicol antibiotics while resistant to nalidixic acid, streptomycin and vancomycin antibiotics. The isolates showed slightly low hydrophobicity values (3.63% to 25.62%) but moderate aggregation activity (25.15% to 42.87%). The phylogenetic analysis using 16S ribosomal ribonucleic acid (16S rRNA) gene and internal transcribed spacer (ITS) gene sequences revealed that all belacan (BE) and bosou (BO) isolates were identified as Lactiplantibacillus plantarum, while all non-cooked budu (BUM) isolates were identified as Lacticaseibacillus paracasei. The isolates were further evaluated for their cholesterol-lowering properties and interactions with the human colorectal adenocarcinoma cell line HT-29. Although all strains did not show bile salt hydrolase (BSH) activity, they were able to grow with varying abilities on the MRS agar supplemented with taurodeoxycholic acid and glycodeoxycholic acid, as well as remove cholesterol in the MRS medium quite promisingly. Through principal component analysis, L. plantarum strain BE7, L. plantarum strain BO1 and L. paracasei strain BUM6 were chosen as the potential isolates to be further explored according to their distinctive properties. The probiotic nature of these three LAB strains was strengthened by its adherence to the HT-29 cell lines. The characteristics were proved quantitatively by growing the isolates on MRS agar, with the adhesion percentages ranging from 24.7% to 39.6%, as well as qualitatively via FESEM observations. The cytotoxicity of the isolates towards HT-29 cell lines was also investigated using the MTT assay, with the findings obtained showing that all isolates could only cause cytotoxicity at exceptionally high concentrations (108 and 109 CFU/mL). In the transcriptomic profile analysis using qPCR, L. plantarum strain BE7, L. plantarum strain BO1, and L. paracasei strain BUM6 demonstrated the ability to downregulate the CD36 and NPC1L1 mRNA expression by HT-29 cell lines following 6 h exposure to the isolates, as well as upregulate the NR1H3 mRNA expression and reduce the SCARB1 mRNA expression after a longer treatment duration, which is 24 h. These data indicated that L. plantarum strain BE7, L. plantarum strain BO1 and L. paracasei strain BUM6 have probiotic characteristics with cholesterol-reduction potential, proving their prospective as probiotics for the food industry and alternative treatment in the management of hypercholesterolemia.en-USLactic acid bacteriaFermented foods -- Chemistry, AnalyticThesis