RICERCA E TIPIZZAZIONE GENETICA DI BATTERI LATTICI ISOLATI DA FORMAGGI TIPICI SICILIANI E VALUTAZIONE DELLA PRODUZIONE DI BATTERIOCINE

Sicily, due to its millenarian history and radicated traditions, results one of the regions with an elevated variety of tipic cheeses. Lactic acid bacteria that are present into this variety of products play a fundamental role during the process of cheese making. This kind of lactic acid bacteria are now increasingly studied for their production of inhibitory-activity substances: the bacteriocines. The term “bacteriocine” generally indicates the proteinaceous molecules bacteria produced that are generated by both Gram-positive and Gram-negative bacterias, and with an inhibitory-activity against bacteria strains that are different from the producer one. The research in the present study aims to identificate lactic-bacteria strains that are isolated by the traditional Sicilian cheeses and that result bacteriocine-producing. The identification of the bacteria has been effectuated by mean of the sequencing of gene 16rRNA, starting from the ampliconi obtained by the primer ITS for / ITS rev. The determination of the bacteriocine production, using the agar-spot test method, has been effectuated on 100 of the isolated and identificated strains. The bacteriocine resulted has been characterized through the identification of the title (expressed in AU/ml), through the trial at different temperatures and ph values, and through the trial of sensibility to enzymes. The results shown a little heterogeneity of the Lactococcus and Enterococcus species and, by contrast, an elevated presence of different species of Lactobaccilus. The batteriocine production has been found only for one strain (n. 124) of the Lactococcus lacts subsp. Lactis specie and for the indicator bacteria Staphylococcus aureus. The characterization tests have shown that the bacteriocine produced is heat-stable, and belongs so to Group II, and that it maintains its inhibitory activity in a large range of idrogenionic concentration; it also has a proteic nature, because it is inhibited by the proteolitic enzymes by wich it has been tested. The results is the wished one, because among the analyzed strains, it had been noted that it is the Lactococcus lactis. Subsp. Lactis that fits the required characteristics. The individuated batteriocine results, infact, heath-stable and is it thus possible to use it on different temperatures of lavoration: for the productive process of row milk (e.g. caciotta) and of the stretched cheese (e.g. caciocavallo of Palermo), too. This purpose was born from the willing to analyze the possibility that the producer strain may be utilized ad an autocton starter, preserving the qualitative chataceristics of the product, and to analyze also the possibility to find an antagonist of the patogena microflora.