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Low, Siew Jean (2021) Understanding the in vitro gastrointestinal transit tolerance of putative lactic acid bacteria isolated from Malaysian fermented foods. MRes thesis, University of Nottingham.

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Abstract

Probiotics are defined as living microorganisms that when consumed in adequate amounts will exhibit health benefits to the host. Probiotics are known to play important roles in relief of lactose intolerance symptoms and improving gut health. However, till today the beneficial effect of probiotic bacterium is strain-specific, no single probiotic is able to resolve all gut health issues. Hence, the search for a stronger and more potent of probiotic bacterium is essential. Hence, the current study is aimed to isolate putative lactic acid bacteria from local fermented foods, namely tempeh and tapai ubi, and investigate the ability of these LABs to tolerate the upper gastrointestinal transit in an in vitro setting prior to future use as probiotics. A total of 18 putative LABs were isolated from tempeh and tapai ubi using spread plate method with MRS selective medium. However only four isolates remained viable after frozen storage and was proceeded for subsequent studies.

Three of the putative LABs were isolated from tapai ubi and designated as SU1, SU2, and SU8, and the putative LAB isolated from tempeh was designated as ST4. The identity of these four putative isolates were determined using 16s rRNA gene sequence analysis. SU1 and SU2 were identified as Pediococcus acidilactici with 80% and 87% similarity. SU8 was identified as Pediococcus claussenii with 82% similarity while ST4 was identified as Leuconostoc mesenteroides subsp. mesenteroides with 88% similarity.

After identification, the ability of these putative LAB isolates to survive the bile, gastric and small intestinal transits were evaluated in an in vitro setting. SU8, SU1 and SU2 were able to tolerate 0.5% of bile salt condition with growth ranging from 5.70 to 7.13 Log10CFU/ml after 24h of incubation, except for ST4. ST4 was susceptible to 0.5 and 1.0% of bile salt. These putative LAB isolates were highly tolerant to the simulated gastric transit ranging from pH 2 to 4 and maintained a growth of more than 12 Log10CFU/ml after 180 min of incubation. All four putative LAB isolates were able to tolerate the simulated small intestinal transit with addition of 0.3% bile salt and maintained a growth of more than 9 Log10CFU/ml after 240 min of incubation. ST4 had the highest tolerance to the simulated small intestinal transit and therefore exhibited a putative potential as probiotics. Future study will need to be conducted to understand the health benefits exhibited by these putative LAB isolates for application as probiotics.

Item Type:	Thesis (University of Nottingham only) (MRes)
Supervisors:	Lim, Yin Sze
Keywords:	lactic acid bacteria, fermented food, probiotic bacterium, intestinal transits
Subjects:	Q Science > QR Microbiology
Faculties/Schools:	University of Nottingham, Malaysia > Faculty of Science and Engineering — Science > School of Biosciences
Item ID:	61217
Depositing User:	LOW, Siew
Date Deposited:	24 Feb 2021 04:40
Last Modified:	24 Feb 2021 04:40
URI:	https://eprints.nottingham.ac.uk/id/eprint/61217

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