Genotypic and probiotic characterisation of lactobacilli strains isolated from traditional Algerian products

Twelve bacterial strains isolated from two different traditional Algerian products, cow butter and fermented wheat, were genetically identified using PCR and 16S rRNA sequencing. The growth kinetics of these strains were studied with two different carbon sources, lactose and glucose, each at a concentration of 2 %, alongside evaluations of their probiotic properties and safety. Genotypic identification revealed the presence of three species: Levilactobacillus brevis (4 strains), Lactiplantibacillus plantarum (2 strains), and Lacticaseibacillus paracasei (6 strains). Lp. plantarum and L. paracasei strains showed robust growth on both carbon sources, with similar performance, while L. brevis strains exhibited reduced growth in MRS broth containing lactose compared to MRS broth with glucose. Additionally, all strains demonstrated excellent tolerance to simulated gastric conditions and bile salts, with survival rates above 90 %. However, the L. brevis 64 strain was the most affected by bile salts compared to the other strains, showing a significant decrease in survival rate. Safety evaluations revealed no DNase or β-hemolytic activity, and the strains were generally sensitive to most antibiotics tested. These strains, particularly Lp. plantarum and L. paracasei, isolated from lesser-studied Algerian fermented foods, exhibit promising in vitro probiotic traits and contribute to diversifying available functional microbial resources.