Probiotic characterization and in vitro functional properties of lactic acid bacteria isolated in Thailand

Fourteen lactic acid bacteria isolated from fermented foods and healthy animal feces in Thailand were characterized for their potential as probiotics. The 16S rRNA gene sequence analyses identified them as Lactiplantibacillus, Levilactobacillus, Limosilactobacillus, Lacticaseibacillus, Campanilactobacillus, Pediococcus, and Enterococcus genera. All strains survived in simulated gastrointestinal fluid (pH 2) and bile salt solution (pH 8) at over 70% and 63%, compared with initial cell concentration, respectively. In vitro adhesion testing showed their adhesive property of over 70%, while the results of antibiotic susceptibility indicated that all strains were susceptible to amoxicillin, ampicillin, erythromycin, chloramphenicol, clindamycin, imipenem, kanamycin, norfloxacin, penicillin, tetracycline, and vancomycin. All strains exhibited antimicrobial ability against Staphylococcus aureus TISTR 1466, Listeria monocytogenes TISTR 2196, Escherichia coli TISTR 780, Salmonella Enteritidis TISTR 2202, and Salmonella Typhimurium TISTR 292. Moreover, Limosilactobacillus reuteri MF67.1 and Companilactobacillus farciminis R7-1 showed bile salt hydrolase activity. Cellfree culture supernatants of all 14 strains were screened for immunomodulating effects on Tumor Necrosis Factor alpha (TNF-alpha) production. Lactiplantibacillus paraplantarum R26-3 and Lacticaseibacillus zeae M2/5 showed high inhibition of TNF-alpha production at 34% and 29% reduction, respectively; while the other 12 strains decreased TNF-alpha production at various lower levels. Results suggested that all 14 strains met the general criteria of probiotics. Lac. zeae M2/5, Lac. paraplantarum R26-3, Lim. reuteri MF67.1, and Com. farciminis R7-1 were interesting candidates for further studies as anti-inflammatory (M2/5, R26-3) or cholesterol-reducing agents (MF67.1, R7-1) in in vivo animal models.