Usefulness of a set of simple in vitro tests for the screening and identification of probiotic candidate strains for dairy use

A set of simple in vitro tests (identification by species-specific PCR, genetic diversity, phage sensitivity, growth and viability in milk, resistance to salts and flavor compounds, bacterial interactions, tolerance to simulated gastric juice and bile, bile salts deconjugation, hydrophobicity and β-galactosidase and antibacterial activities), that can be carried out in almost every laboratory of microbiology, mainly in developing countries where there is often limited access to sophisticated techniques, allowed us to identify, among 19 intestinal human isolates, a potential candidate for new probiotic dairy foods for the local market. Lactobacillus gasseri LgF_37/1 performed well in the culture media used for the enumeration of probiotic bacteria in argentinian dairy products. This strain showed also high tolerance to the technological challenges assessed, bile salts resistance, the capacity to produce bacteriocin-like metabolites, to inhibit pathogenic bacteria, to deconjugate bile salts and high hydrophobicity. Further in vivo research should be carried out with this strain before claiming probiotic properties for it. However, the use of a set of simple in vitro techniques proved to be important to determine which strains should undergo future and more complex studies.