Thongaram T.
Silpakorn University, Bangkok, Thailand

Probiotics are proposed to have a wide range of health benefits. Their benefits have been proven effective in supporting immune function and digestive system. Currently, much attention is paid to the role of probiotics in human health improvement and treatment of human disease. Researches effort allowed to obtain sufficient numbers of well-characterized probiotic strains available for application in functional foods and health-associated products. However, the isolation and characterization of new strains are still needed. The aim of this study was to characterize the probiotic characteristics of lactic acid bacteria from traditional fermented vegetable.

Isolation of lactic acid bacteria
Sixteen samples of Thai traditional fermented vegetable products were obtained from the local markets of Thailand central region. 10 g of sample were weighed aseptically and homogenized for 2 min in stomacher containing 90 ml of peptone water. The homogenized samples were serially diluted and pour-plated on MRS (de Man, Rogosa and Sharpe) agar and were incubated at 37°C for 48-72 h.
Resistance to low pH
Cultures of all lactic acid bacteria strains were cultivated for 24 h in MRS medium, centrifuged, washed twice with PBS buffer and re-suspended to a final concentration 10ˆ7-10ˆ8 CFU/ml in PBS. Bacteria were incubated in 0.85% NaCl at pH 2.5 for 4 h at 37°C.
Antimicrobial activity
Inhibition of pathogens of the selected lactic acid bacteria strains was analyzed in the cell-free supernatant (CFS), obtained from cultures of the isolates in MRS broth. After 24 h of incubation at 37°C, the CFS were recovered by centrifugation (10,000 rpm for 10 min). The nutrient agar plates were inoculated with pathogenic bacteria, air-dried and 6 mm diameter wells were punctured in each plate and 50 μl of cell free supernatant (CFS) were placed in each well and incubated for 24 h at 37°C.

A total thirty-two lactic acid bacteria strains were isolated from fermented vegetable products and twelve isolates were evaluated for probiotic potential with the resistance to low pH and antimicrobial activity. The studies on resistance to gastrointestinal condition
showed that isolate MCSU4 exhibited high tolerance to the simulated gastric juice (pH 2.5) and high concentration of NaCl (10 and 15%). Interestingly, while in the simulated gastric condition isolate MCSU4 could survive 4 h at pH 2.5. All of the selected lactic acid bacteria strains showed various antibacterial activities against five pathogens; Bacillus subtilis ATCC 6633, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853,Salmonella typhimurium ATCC 13311, and Staphylococcus aureus ATCC 25953, however only isolate MCSU4 possessed the highest activity of inhibiting pathogens.

Among the selected strains, isolate MCSU4 showed the best probiotic potential with the high tolerance to simulated gastrointestinal juice and high concentration of NaCl and also broad antimicrobial activity. Results revealed that isolate MCSU4 is ideal probiotic candidate and requires further in vitro and in vivo safety studies.

Keywords: Probiotics, Lactic acid bacteria, Gastrointestinal condition, Low pH, Antimicrobial activity

Thongaram T. (2016). In vitro evaluation of selected probiotic properties of lactic acid bacteria isolated from thai traditional fermented vegetable. Conference Proceedings of IPC2016. Paper presented at the International Scientific Conference on Probiotics and Prebiotics, Budapest (p. 120.). IPC2016

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