Is there any still undisclosed biodiversity in Ciauscolo salami? A new glance into the microbiota of an artisan production as revealed by high-throughput sequencing.

Ciauscolo is a fermented sausage with the Protected Geographical Indication (PGI) status. To disclose the microbial ecology of a model Ciauscolo salami manufacture during its natural fermentation, viable counting, amplicon-based sequencing and real-time PCR were applied. The volatilome during fermentation was also characterized. The results allowed previously undetected species to be discovered. The core microbiota was composed by Lactobacillus algidus, Leuconostoc carnosum, Lactobacillus sakei, Debaryomyces hansenii, Glomus hyderabadensis, Tilletiopsis washingtonensis, and Kurtzmaniella zeylanoides. Salmonella spp. and Listeria monocytogenes were absent in all the samples; moreover, multiplex real-time PCR revealed the absence of the target genes bont/A, bont/B, bont/E, bont/F, and 4gyrB (CP), encoding botulinic toxins. Volatilome, deeply depending on microbiological metabolism, was characterized by spices-derived components. Limonene, sabinene, α- and ß-pinene, 3-carene, and α-thujene were the most represented monoterpene hydrocarbons, whereas ß- and α-copaene were the most represented sesquiterpene hydrocarbons. Allyl methyl sulphide and diallyl disulphide were the major aliphatic sulphur compounds, together with diallyl sulphide and allyl methyl disulphide.

The microbial ecology of a typical Italian salami during its natural fermentation.

We have investigated the bacteria and yeast ecology of the typical Italian Ciauscolo salami that is produced in Central Italy using a polyphasic approach based on culture-dependent and -independent methods. The physico-chemical analyses showed a progressive drop in pH and water activity (aw) during ripening. The viable counts revealed a dominance of lactic acid bacteria (LAB) over coagulase negative cocci (CNC) and yeasts. From the molecular identification of the isolates, the prevalence of Lactobacillus curvatus, Lb. plantarum and Staphylococcus xylosus was shown among the bacteria, while Debaryomyces hansenii was the prevalent species among the yeasts, and it was isolated throughout the whole ripening process. Minority species, namely Rhodotorula mucillaginosa and Trichosporon brassicae, were also recovered from the meat batter. The total microbial community was profiled without cultivation by analyzing the DNA that was directly extracted from the salami samples. Moreover, the cultivable community was profiled by analyzing the DNA recovered from bulk cells that were obtained by harvesting the colonies from serial-dilution agar plates. The 16S rRNA gene V1 and V3 regions were used as targets in the denaturing gradient gel electrophoresis (DGGE) profiling of the LAB and CNC communities, respectively, while the diversity and dynamics of the yeast population were assessed by analyzing a portion of the 28S rRNA gene. Our findings suggest that the microbial diversity of fermented meat products can be successfully investigated by this polyphasic approach that is based on the assessment of both the total and the cultivable community diversity.

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.