Application of 16S-ARDRA and RFLP-PFGE for improved genotypic characterisation of dairy propionibacteria and combination with characteristic phenotypes

Propionic acid bacteria (PAB) are important for the manufacture of Swiss-type cheeses since they are involved in the formation of eyes and are responsible for the characteristic flavour and aroma of these cheeses. Propionibacterium freudenreichii is most commonly encountered in Swiss-type cheeses and is the sole Propionibacterium species used as a cheese starter. Aspartase activity determined in PAB is strain-dependent and it is important to find a usable way to identify the specific strains involved in cheese making. In this work, 16S-amplified ribosomal DNA restriction analysis and pulsed-field gel electrophoresis (PFGE) were used to differentiate 107 PAB strains. Consequently, the presence and persistence of inoculated Propionibacterium starter strains can be monitored during cheese ripening. The studied metabolic features of lactose utilisation, nitrate reductase activity and aspartase activity could not be directly associated with particular genotypes, but principal component analysis (PCA) suggested a linkage between related PFGE patterns and aspartase activity.