71A-14 |
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E. P. BRICZINSKI and R. F. Roberts. Dept. of Food Science, Pennsylvania State Univ., 121 Borland Lab., University Park, PA 16802-2504 Increasing application of probiotics in food highlights the need for reliable methods to identify and differentiate probiotic microbes. Nucleic acid-based techniques are increasingly important in differentiating and typing bacteria and providing means for evaluating inter- and intra-species relatedness. PCR-based techniques and pulsed-field gel electrophoresis (PFGE) have been successfully used to characterize strains of bifidobacteria. This study employed PCR and PFGE as nucleic acid-based techniques for characterizing bifidobacteria. More traditional phenotype-based methods, including growth on various media and fermentation of carbohydrate substrates, were also used to characterize strains of bifidobacteria from culture collections and commercial culture suppliers. Twenty-two commercial strains, identified as belonging to six different species, were obtained from six different commercial suppliers. The presence of fructose-6-phosphoketolase (F6PPK) and the presence of a genus-specific sequence of 16S rDNA using PCR identified the strains as belonging to the genus Bifidobacterium. Strains were also characterized by determination of organic acid production, ability to ferment carbohydrate sources, ability to grow on various media, and PFGE. PCR with species-specific primers was used to determine species identity. Thirteen strains, representing six species of bifidobacteria, were obtained from culture collections and were also assayed as described above. Twenty of the twenty-two strains obtained from commercial suppliers were identified as Bifidobacterium lactis by PCR using species-specific primers. Phenotypic methods were not effective in differentiating among species of bifidobacteria. Within the commercial strains of B. lactis, analysis of the PFGE profiles revealed one pattern type each with XbaI and SpeI, indicating a high level of relatedness among these strains. Only four of the twenty-two commercial samples were correctly identified by their suppliers. More effective methods of identifying strains of bifidobacteria are needed for the starter culture industry. PFGE, while able to differentiate between bifidobacteria species, was not able to differentiate among commercially-used strains of B. lactis.
Session 71A, Dairy Foods: General
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |