ABSTRACT
Ripened sheep sausages are widely consumed in Italy, particularly in Sardinia. Despite their driving role in flavor and color development, coagulase-negative staphylococci in these products have been rarely investigated. A total of 70 CoNS cultures isolated from Sardinian sheep sausages were characterized by rep-PCR and M13-RAPD typing and identified by 16S rDNA sequencing. S. xylosus and S. equorum accounted for more than 70% of the total isolates, whilst S. pasteuri (8.5%), S. succinus (2.8%), and S. haemolyticus (2.8%) were less represented. The genes encoding the synthesis of putrescine, tyramine, cadaverine, and histamine were evaluated by PCR. None of the strains hosted genes for decarboxylases, except one S. pasteuri strain that was potentially a tyramine-producer. Antibiotic resistance was evaluated, along with nitrate reductase, lipolytic, and proteolytic activity, in a pool of selected cultures. Resistance to the primary antibiotics was rather widespread. S. xylosus, S. equorum, and S. pasteuri strains were all resistant to amoxicillin and kanamycin. S. equorum strains were sensitive to all tested antibiotics. S. xylosus strains were all resistant to penicillin B. Conversely, all S. pasteuri strains were resistant to both ampicillin and penicillin B, and four out of five strains exhibited tetracycline resistance. The high variability in the production of sheep sausages makes the search for adjunct cultures of crucial relevance. According to this perspective, the characterization of the autochthonous CSN population represents the first step to approach a starter selection.
ABSTRACT
The aim of this work was to identify and characterize, from a technological and safety point of view, the lactic acid bacteria (LAB) isolated from traditional sheep-fermented sausage. First, LABs were identified then were screened for some technological parameters such as acidifying and growth ability, proteolytic and lipolytic activity and for antimicrobial activity. Finally, biogenic amine production and degradation abilities were also evaluated. This research reveals the predominance of Lactiplantibacillus (L.) plantarum on LAB community. Almost all L. plantarum strains were active against Listeria monocytogenes strains (inhibition zone diameters > 1 cm). None of the tested strains were positive in histidine (hdcA), lysine (ldc) and tyrosine (tyrdc) decarboxylase genes and only one (L. plantarum PT9-2) was positive to the agmatine deiminase (agdi) gene. Furthermore, given the positive results of the sufl (multi-copper oxidase) gene detection, all strains showed a potential degradation ability of biogenic amines.
