Characterization of Streptococcus macedonicus strains isolated from artisanal Italian raw milk cheeses.

The aim of this research was to elucidate the potential technological role of Streptococcus macedonicus in cheese. For this purpose, phenotypic and randomly amplified polymorphic DNA (RAPD)-PCR subtyping as well as biochemical characterization were carried out on 37 S. macedonicus isolates collected from several artisanal, Italian raw milk cheeses. Identification was achieved by a species-specific PCR assay developed in this study. A wide phenotypic and genotypic heterogeneity between the isolates was observed. A certain variability of the acidifying and peptidase activities was observed and the comparison between some technological characteristics displayed by S. macedonicus and Streptococcus thermophilus indicated a clear distinction of these species. The presence of dairy grade characteristics, such as peptidase activities, ability to produce inhibitory compounds, absence of antibiotic resistance and haemolytic activity, may suggest the rational design of a novel starter culture for dairy application composed of strains of both S. macedonicus and S. thermophilus species, with the former used as a starter adjunct