RESUMO
One of the traditional ways of preparation of yogurt starter in Bulgaria is placing a branch of a particular plant species into boiled sheep's milk maintained at about 45 degrees C, which is further incubated until a dense coagulum is obtained. To investigate the possible origin of the yogurt starter bacteria, Lactobacillus delbrueckii ssp. bulgaricus (L. bulgaricus) and Streptococcus thermophilus (S. thermophilus), the traditional way of yogurt-starter preparation was followed. Hundreds of plant samples were collected from four regions in Bulgaria and incubated in sterile skim milk. The two target bacteria at low frequencies from the plant samples collected were successfully isolated. Phenotypic and genotypic characteristics of these bacterial isolates revealed that they were identified as L. bulgaricus and S. thermophilus. Twenty isolates of L. bulgaricus and S. thermophilus, respectively, were selected from the isolated strains and further characterized with regard to their performance in yogurt production. Organoleptic and physical properties of yogurt prepared using the isolated strains from plants were not significantly different from those prepared using commercial yogurt-starter strains. It was therefore suggested that L. bulgaricus and S. thermophilus strains widely used for commercial yogurt production could have originated from plants in Bulgaria. To our knowledge, this is the first report on the isolation and characterization of L. bulgaricus and S. thermophilus strains from plants.
Assuntos
Lactobacillus delbrueckii/isolamento & purificação , Plantas/microbiologia , Streptococcus thermophilus/isolamento & purificação , Animais , Bulgária , Eletroforese em Gel de Campo Pulsado , Genótipo , Geografia , Lactobacillus delbrueckii/classificação , Lactobacillus delbrueckii/genética , Leite/microbiologia , Fenótipo , Reação em Cadeia da Polimerase , Streptococcus thermophilus/classificação , Streptococcus thermophilus/genética , Iogurte/microbiologia , Iogurte/normasRESUMO
We have found a new growth stimulator for bifidobacteria in the culture broth of Propionibacterium freudenreichii ET-3. The bifidogenic growth stimulator (BGS) was purified by Diaion HP-20 column chromatography and preparative HPLC. Spectroscopic methods including 1H-NMR, UV, and LC-ESI-MS experiments indicated that the chemical structure of the bifidogenic growth stimulator was 1,4-dihydroxy-2-naphthoic acid (DHNA). Approximately 10 mg/L of DHNA was found to be produced in the culture broth of P. freudenreichii ET-3.
