Isolation and identification of lactobacillus and bifidbacteria in probiotic foods avaliable in the brazilian market. / Isolamento e identificação de lactobacilos e bifidobacterias em alimentos probioticos disponiveis no mercado brasileiro.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

In the period between March and May 2001, a series of lactic cultures were isolated from 11 different brand products purchased from regular retail outlets located in Campinas (SP, Brazil). The sample types collected included 3 yogurts, 5 fermented milks, 2 dairy beverages and 1 symbiotic dry mix. The strains were identified by phenotypic and genotypic characteristics, in addition to being submitted to tests to investigate whether they fulfill the minimum prerequisites for microorganisms to be considered probiotic, i.e. resistance to pH, resistance to bile and bacteriocin production. Phenotypic identification (36 strains) using the API 50CHL Identification Kit (BioMérieux) evidenced the presence of the following species: 1o) Lactobacillus paracasei subsp. paracasei - isolated from 6 products, 2o) Streptococcus thermophilus - isolated from 4 products, 3o) Leuconostoc mesenteroides subsp.cremoris - isolated from 3 products, 4o) Lactobacillus rhamnosus, Lactobacillus acidophilus and Lactococcus lactis subsp.lactis - isolated from 2 products each, 5o) Lactobacillus delbrueckii subsp.bulgaricus, Lactobacillus delbrueckii subsp. lactis, Leuconostoc lactis and Lactobacillus curvatus subsp. curvatus - isolated from 1 product each. Identification on the basis of genotypic characteristics (41 strains, 36 of which isolated from products and 5 standard strains from a culture collection) using an automated ribotyping method RiboPrinter® microbial characterization system, (Dupont/Qualicon) produced the following results: two strains could not be typed by the Riboprinter method (identified as Leuconostoc mesenteroides subsp. cremoris by API 50CHL). Five strains were typed but not identified by the Riboprinter system (identified as Leuconostoc mesenteroides subsp. cremoris and Lactobacillus acidophilus by API 50CHL). Three strains were identified as Lactobacillus only to the genus level (identified as Lactobacillus delbrueckii subsp. lactis and Lactobacillus acidophilus by API 50CHL). The remaining strains were identified to the species level, 63% with the same results as those obtained with API 50CHL and 37% with discordant results. Most of the discordant results between the two identification methods were generated by the strains identified by API 50CHL as Leuconostoc mesenteroides (subsp. cremoris and lactis), Streptococcus thermophilus, Lactobacillus acidophilus and Lactobacillus delbrueckii subsp. bulgaricus. The strains with concordant results were predominantly those identified by API 50CHL as Lactobacillus rhamnosus and Lactobacillus paracasei subsp. paracasei, while the strains producing discordant results were mainly those identified by API 50CHL as Leuconostoc, Streptococcus thermophilus, Lactobacillus acidophilus and Lactobacillus delbrueckii subsp. lactis. One strain of Bifidobacterium bifidum (KCTC 3440) was correctly identified by the Riboprinter system, whereas 1 strain of Bifidobacterium subtile (ATCC 27537) was incorrectly identified as Enterococcus faecium. Most of the 36 strains evaluated for resistance to pH showed complete loss of viability after 1 to 3 hours at pH 1,0 or 2,0. At pH 3,0 the survival rate was considerably greater. Two criteria were used for drawing conclusions relative to the probiotic potential of the strains. According to the first criterion, strains exhibiting an 80% survival rate (reduction factor smaller than 0.1 log) after exposure for 3 hours to pH 3 or 1% bile. Based on this criterion, none of the strains isolated could be considered probiotic. According to the second criterion, resistance to pH 3 for 90 minutes and in the presence of 0,1% bile (24h), without reduction in viable counts, indicates potentially probiotic strains. Based on this latter criterion, two strains were found to exhibit probiotic potential, one strain of Lactobacillus rhamnosus and another of Lactobacillus acidophilus. A total of 29 strains were evaluated for bile resistance and the conclusions of the test results produced were based on two different criteria. According to the first, strains presenting an 80% survival rate (reduction factor smaller than 0,1 log) after 3 hours exposure to 1,0% w/v bile and pH 3,0 are considered resistant. Based on this criterion, none of the 29 strains isolated was found to be resistant to bile. According to the second criterion, cultures presenting growth in the presence of 1% Oxgall, equal or greater than 20% of that produced by the control, are considered resistant (reduction factor smaller than 0,7 log). Based on this criterion, 7 (24%) of the 29 strains isolated from products were found to be resistant: one strain of L.acidophilus, one of L.rhamnosus, one of L.paracasei subsp. paracasei, one of Streptococcus thermophilus, one of Lactococcus lactis subsp. lactis and two strains of Leuconostoc mesenteroides subsp cremoris. Thirty-two strains were tested for bacteriocin production, all of which gave negative results. The results of the test performed to evaluate antagonism against some species of Gram-negative and Gram-positive pathogenic bacteria showed that one strain of L.rhamnosus inhibited Listeria, while another strain of L.rhamnosus inhibited both Listeria and S. aureus. No inhibition of Gram-negative bacteria (E. coli e Salmonella) was found.

ASSUNTO(S)

ribotipagem probiotics bifidbacteria riboprinter bifidobacterias lactobacilo lactobacillus riboprinter probioticos ribotyping

ACESSO AO ARTIGO

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