Caratterizzazione Genotipica e Fenotipica di Ceppi di L. rhamnosus di Origine Umana e Alimentare

The aim of the present study was to investigate the dual role of Lactic Acid Bacteria in food fermentation processes and in health-promoting effects on human host. In the first part of this PhD thesis will be described the role of spontaneous lactic acid microflora developed during fermentation of two traditional fermented foods: Pecorino Crotonese cheese and Table Olives, cultivar Nocellara Etnea and Geracese . The employment of culture-independent methods such as Denaturing Gradient Gel Electrophoresis (DGGE), gives the opportunity to trace the evolution of lactic acid microflora during the ripening of these traditional foods. Next to this, physical and chemical analyses have been integrated in order to highlight the main changes in food matrix and relate them as a consequence of microbial fermentation. The second part of this study will focus on the analysis of probiotic factors of L. rhamnosus, a well-known and documented beneficial microorganism. Considering that L. rhamnosus is a multi niche species, several strains have been recovered from different sources such as fermented foods (Pecorino Crotonese cheese) and clinical samples and compared at genotypic and phenotypic level with the further aim to understand the evolution and the ecological versatility of this species. Moreover L. rhamnosus strain GG and L. casei are two species widely marketed as probiotics, and a comparative analysis of some health-promoting traits will be provided in order to highlight differences in their claimed beneficial effects.