No abstract

This study evaluated the probiotic properties (stability at different pH values and bile salt concentration, auto-aggregation and co-aggregation, survival in the presence of antibiotics and commercial drugs, study of β-galactosidase production, evaluation of the presence of genes encoding MapA and Mub adhesion proteins and EF-Tu elongation factor, and the presence of genes encoding virulence factor) of four LAB strains (Lactobacillus casei SJRP35, Leuconostoc citreum SJRP44, Lactobacillus delbrueckii subsp. bulgaricus SJRP57 and Leuconostoc mesenteroides subsp. mesenteroides SJRP58) which produced antimicrobial substances (antimicrobial peptides). The strains survived the simulated GIT modeled in MRS broth, whole and skim milk. In addition, auto-aggregation and the cell surface hydrophobicity of all strains were high, and various degrees of co-aggregation were observed with indicator strains. All strains presented low resistance to several antibiotics and survived in the presence of commercial drugs. Only the strain SJRP44 did not produce the β-galactosidase enzyme. Moreover, the strain SJRP57 did not show the presence of any genes encoding virulence factors; however, the strain SJRP35 presented vancomycin resistance and adhesion of collagen genes, the strain SJRP44 harbored the ornithine decarboxylase gene and the strain SJRP58 generated positive results for aggregation substance and histidine decarboxylase genes. In conclusion, the strain SJRP57 was considered the best candidate as probiotic cultures for further in vivo studies and functional food products development.

The probiotic potential of Leuconostoc mesenteroides subsp. mesenteroides SJRP55, isolated from water buffalo mozzarella cheese was evaluated. The microorganism presented resistance to stressful conditions that simulated the gastrointestinal tract, and to the best of our knowledge, Leuconostoc mesenteroides subsp. mesenteroides SJRP55 was the first of this species with the ability to deconjugate bile salts. Tolerance to NaCl was temperature dependent, as well the results obtained by aggregation capacity. The strain presented good adhesion properties, β-galactosidase activity, viability in fermented milk during storage, inactive against Streptococcus thermophilus and sensitive to most of the tested antibiotics. Some analgesic medications inhibited the growth of the strain. Leuconostoc mesenteroides subsp. mesenteroides SJRP55 exhibited in vitro probiotic potential, and it can be better characterized through future in vivo tests. This bacterium presents higher functional properties compared to other studied strains, and therefore, it is a potential candidate for the application as a probiotic strain, which could be used by industries in the manufacture of functional milk-based products.