Sara Santarelli

Investigation of the microbial ecology of Ciauscolo, a traditional Italian salami, by culture-dependent techniques and PCR-DGGE

The microbial ecology of 22 samples of commercially available Ciauscolo salami were investigated using a polyphasic approach, based on culture-dependent and -independent techniques. The viable counts of pathogen and hygiene indicator microorganisms highlighted the adequate application of good manufacturing practices, while the viable counts of the lactic acid bacteria, coagulase negative cocci, and yeasts showed dominance of the first of these microbial groups. Bacterial and fungal DNA were extracted directly from the salami and amplified by PCR, using two primer sets targeting the 16S and 28S rRNA genes, respectively. Denaturing gradient gel electrophoresis (DGGE) and sequencing of selected bands were used to investigate the microbial ecology of these Ciauscolo salami. The most frequently found bacterial species were Lactobacillus sakei and Lb. curvatus, while Debaryomyces hansenii was the prevalent yeast species detected. Cluster analysis of the DGGE profiles and calculation of biodiversity indices allowed the degree of microbial similarity across these salami to be determined.

Bacterial dynamics in a raw cow's milk Caciotta cheese manufactured with aqueous extract of Cynara cardunculus dried flowers.

Aims:  To investigate the bacterial dynamics of a Caciotta cheese traditionally manufactured in the Montefeltro area (Central Italy) with raw cow’s milk and an aqueous extract of dried flowers from Cynara cardunculus as a coagulating agent.

Characterisation of Lactobacillus helveticus strains producing antihypertensive peptides by RAPD and inverse-PCR of IS elements

Lactobacillus helveticus is used for the manufacture of cheeses and milk-based products. Although it is not considered a probiotic microorganism, some strains demonstrated beneficial effects through the production of antihypertensive peptides from the hydrolysis of casein during milk fermentation. Strain-specificity of bioactive peptide production by L. helveticus makes the availability of reliable typing methods essential for both legal and good manufacturing processes. Accordingly, RAPD and inverse-PCR of five insertion sequence elements were comparatively evaluated for the molecular characterisation of four L. helveticus dairy cultures producing antihypertensive peptides and fourteen reference strains. Calculation of discriminatory indices and cluster analysis of the DNA fingerprints confirmed the suitability of both approaches for acceptable strain differentiation. Although RAPD was more discriminating, for a few test strains a neat discrimination was only achieved through multiplex inverse-PCR, thus suggesting the suitability of a combined analytical approach for a finer strain discrimination.