Probiotic Characterization And Safety Assessment of Lactococcus Lactis Subsp. Lactis R7 Isolated From Ricotta Cheese

Abstract

The aim of this study was to identify and characterize in vitro Lactococcus lactis R7 isolated from commercial ricotta cheese. The results from phenotypic characterization demonstrated that L. lactis R7 had growth potential in a wide temperature range (15 °C and 45 °C), ability to tolerate high osmotic concentrations (sodium chloride 4.0 %), ability to growth in acidic and alkaline condition (pH 2.0 and 9.6), and ability to sugar fermentation (glucose, maltose and ribose). The findings confirm that L. lactis R7 belong to the genus Lactococcus. The results from molecular identification by 16S RNA identified the isolate as Lactococcus lactis subsp. lactis R7. The phenotypic characteristics combined with the molecular identification, indicate that the isolate R7 belongs to the lactis subspecies. The isolate L. lactis R7 was tolerant to acidity and bile salts. In the intestinal tract, cell concentrations were higher than 7.98 log CFU.mL-1 in the presence and absence of bile salts. L. lactis R7 showed antioxidant and inhibitory capacity for lipid peroxidation. It also demonstrated capacity for self-aggregation (25.8%), coaggregation (18.3%) and hydrophobicity (11.1%). The antagonist activity of the isolate was greater against Staphylococcus aureus (12.2 mm), when compared to Escherichia coli (11.1 mm) and Salmonella enteritidis (9.5 mm). In the MTT assays, L. lactis R7 did not show cytotoxicity to VERO cells at the evaluated concentrations. In conclusion, L. lactis R7 isolated from ricotta cheese presented probiotic characteristics and compatible safety aspects for use as a food technology culture.