Evaluation of the probiotic potential of lactic strains isolated from cow's milk

Abstract

The use of lactic acid bacteria (LAB) in the dairy industry has undergone an enormous evaluation in technologically advanced countries. The exploitation of this kind is however very limited in some other countries such as Algeria. This limitation concerns the diversity of products present on the market but also the number of strains introduced in dairy products, this is related to the constraints posed by LAB. To isolate new probiotic strains, samples of cow's milk were subjected to spontaneous fermentation to enrich its LAB. 21 lactic acid isolates active against four pathogenic and food spoilage bacteria were selected from sixty-one isolated LAB, and only ten strains were selected showing considerable adhesive capacities. Indeed, they have moderate to high levels of hydrophobicity. They can all auto-aggregate with percentages ≥85.86 ± 0.59%. The power to co-aggregate with 4 pathogenic strains differs from strain to strain. Thus, strains C2, H9, V5, and L7 showed different percentage levels of 56.06 ± 0.36%, 32.33 ± 0.63%, 22.60 ± 079%, and 6.55 ± 0.20% against B. cereus, S. aureus, P. aeruginosa, and E. coli respectively. They were all resistant to the acidity of the stomach environment and have a good tolerance to 0.3% and 0.5% bile salts. All isolates were able to grow at 0.4% phenols after exposure for 24 h. Only our lactic acid bacteria V1 and V8 showed resistance after exposure to pepsin at pH =2 and all strains at pH =3. The results obtained are interesting which makes our strains presumed probiotic, they can play an important role in the gastrointestinal tract (GIT).