Abstract
The present study aims to evaluate the probiotic potential of some lactic acid bacteria and select the candidates to be used as probiotic bacteria with some prebiotics in the functional foods. Ten of Bifidobacteria and Leuconostoc strains (8 Bifidobacteria and 2 Leuconostoc) were screened for their probiotic potential. The in vitro tests included survival in simulated gastrointestinal tract conditions (low pH, pepsin, bile salts, and phenol), resistance to 6 antibiotics and antimicrobial activity (against Escherichia coli 0157: H7 ATCC 6933, Bacillus cereus ATCC 33018, Staphylococcus aureus ATCC 20231, Pseudomonas aeruginosa ATCC 9027, Salmonella typhimurium ATCC 14028 and Listeria monocytogenes V7 serotype 1). Five selected strains were B. adolescentis a-1, B. longum BB-536, B. longum b-1, B. bifidum Bb 12 and L. mesenteroides subsp. mesenteroides B-512f demonstrated the highest final population (>= 8 log cfu/ml) after exposure to MRSc broth (pH 3) for 3 hrs or when grown in MRSc medium with 0.3% pepsin at pH 3 and after incubation for 24 hr in MRSc medium with 3% bile salts or incubation for 48 hr in MRSc medium with 0.3% phenol. All tested strains exhibited high resistance to four antibiotics (e. g. Amikacin, Norfloxacin, Cefadroxil and Cefoperazone). The other antibiotics, Rifampicin and Oxytetracycline inhibited all five selected strains. Leu. mesenteroides subsp. mesenteroides B-512f had the lowest sensitivity to both Oxytetracycline and Rifampicin compared to the other five selected strains. The cell free supernatant of B. adolescentis a-1 retarded growth of all pathogenic indicators whereas, B. longum b-1 and Leu. mesenteroides subsp. mesenteroides B-512f retarded growth of all pathogenic indicators except Staphylococcus aureus ATCC 20231 and Salmonella typhimurium ATCC 14028 respectively. B. bifidum Bb 12 retarded growths of all pathogenic indicators except Staphylococcus aureus ATCC 20231 and Salmonella typhimurium ATCC 14028 while B. longum BB-536 retarded growth Escherichia coli 0157: H7 ATCC 6933 and Listeria monocytogenes V7 serotype 1 only. The aforementioned five strains stimulated with Inulin and Fructooligosaccharide at 5% for each, while Lactulose was stimulant for B. adolescentis a-1 and Leu. subsp. mesenteroides B-512f without the others strains. Therefore, these strains could be selected for use as probiotics with Inulin or Fructooligosaccharide as prebiotics in functional foods.