Abstract

In recent years, interest in the probiotic lactobacilli has been stimulated by the use of these bacteria in products that are claimed to confer health benefits on the consumer. The objective of this study is to characterize probiotic Lactobacillus sp isolated from fermented millet drink, fresh milk and raw cow milk. All isolates are screened for their probiotic potential activities, including biochemical characterization and antagonistic activity. A total of seven colonies of lactobacilli isolated from twenty samples of fermented millet drink, fresh and raw cow milk were obtained based on their colonial/ morphological and biochemical characteristics. The Lactobacillus isolates obtained from fermented millet drinks are more effective than isolates from fresh milk and cow milk as regards their antagonism or inhibition. The results indicate that microbial identification drastically improved both in quality and effectiveness through the application of molecular methods. Molecular characterization of probiotic strains in phenotypic and physiological characteristics is often with low level of discrimination, probably due to their co-evolution in the same ecological niches. Thus, the nucleotide base techniques provide an accurate basis for phylogenetic analysis and identification. The other specific aim of the study is to analyze a probiotic Lactobacillus sp isolates. The seven selected isolates were identify to species level as Lactobacillus plantarum, Lactobacillus lactis, Lactobacillus acidophilu and Lactobacillus helveticus using API 50CH Kits. Amplified ribosomal DNA restriction analysis (ARDRA) using Alu I (AGCT), Mbo I (GATC) and Msp I (CCGG) restriction enzymes and 16S rDNA gene sequencing was identified Lactobacillus isolates under study. ARDRA screening revealed unique patterns among seven isolates, with the same pattern for some of the isolates. Gene fragments of 16S rDNA of strains representing specific patterns that needed to be sequence to confirm the identification of these species. These results confirmed that ARDRA is a good tool for identification and discrimination of bacterial species isolated from complex ecosystem and between closely related groups.

Key words: Lactobacillus species, probiotic, antagonistic activity, Escherichia coli,Staphylococcus aureus, Klebsiella pneumoniae, Bacillus cereus, and Pseudomonas aeruginosa, phylogenetic.