In vitro evaluation of the probiotic potential of bacteriocin producer Lactobacillus sakei 1.
Lactobacillus sakei 1 is a food isolate that produces a heat-stable antimicrobial peptide (sakacin 1, a class IIa bacteriocin) inhibitory to the opportunistic pathogen Listeria monocytogenes. Bacterial isolates with antimicrobial activity may be useful for food biopreservation  and also for developing probiotics. To evaluate the probiotic potential of L. sakei 1, it was tested for (i) in vitro gastric resistance (with synthetic gastric juice adjusted to pH 2.0, 2.5, or 3.0); (ii) survival and bacteriocin production in the presence of bile salts and commercial  prebiotics (inulin and oligofructose); (iii) adhesion to Caco-2 cells; and (iv) effect on the adhesion of L. monocytogenes to Caco-2 cells and invasion of these cells by the organism. The results showed that L. sakei 1 survival in gastric environment varied according to pH, with  the maximum survival achieved at pH 3.0, despite a 4-log reduction of the population after 3 h. Regarding the bile salt tolerance and influence of prebiotics, it was observed that L. sakei 1 survival rates were similar (P > 0.05) for all de Man Rogosa Sharpe (MRS) broth formulations  when tests were done after 4 h of incubation. However, after incubation for 24 h, the survival of L. sakei 1 in MRS broth was reduced by 1.8 log (P < 0.001), when glucose was replaced by either inulin or oligofructose (without Oxgall). L. sakei 1 was unable to deconjugate  bile salts, and there was a significant decrease (1.4 log) of the L. sakei 1 population in regular MRS broth plus Oxgall (P < 0.05). In spite of this, tolerance levels of L. sakei 1 to bile salts were similar in regular MRS broth and in MRS broth with oligofructose.  Lower bacteriocin production was observed in MRS broth when inulin (3,200 AU/ml) or oligofructose (2,400 AU/ml) was used instead of glucose (6,400 AU/ml). L. sakei 1 adhered to Caco-2 cells, and its cell-free pH-neutralized supernatant containing sakacin 1 led to a significant reduction  of in vitro listerial invasion of human intestinal Caco-2 cells.
Faculdade de Ciências Farmacêuticas de Ribeirão Preto-Universidade de São Paulo, Av. do Café s/n, CEP 14040-903, Ribeirão Preto/SP, Brazil. bruna.carrer@gmail.com
Bruna C
BC
Gomes
Marina R
MR
Rodrigues
Lizziane K
LK
Winkelströter
Auro
A
Nomizo
Elaine C P
EC
de Martinis
D001422:Bacterial Adhesion; D001430:Bacteriocins / Q000096:biosynthesis*; D001647:Bile Acids and Salts / Q000378:metabolism / Q000494:pharmacology*; D018938:Caco-2 Cells / Q000382:microbiology; D015169:Colony Count, Microbial; D005516:Food Microbiology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007444:Inulin / Q000378:metabolism / Q000494:pharmacology; D007778:Lactobacillus / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D050296:Microbial Viability; D009844:Oligosaccharides / Q000378:metabolism / Q000494:pharmacology; D019936:Probiotics
D001430:Bacteriocins; D001647:Bile Acids and Salts; D009844:Oligosaccharides; C120489:oligofructose; D007444:Inulin