Screening, characterization, and in vitro evaluation of probiotic properties of Lactobacillus strains

Abstract

Objective: The aim of the present investigation was to isolate and identify Lactobacillus strains from dairy and cattle dung samples. Potent isolates were selected for screening by antimicrobial activity; selected lactobacilli were further tested for probiotic properties and adhesive attributes. Methods: Lactobacilli were isolated aseptically on specific de man, rogosa and sharpe medium from dairy and cattle dung samples. Isolates were identified by Gram-staining, motility, catalase, endospore, and carbohydrate fermentation tests. Further, the isolates were screened for antimicrobial activity by disk diffusion assay, and potent lactobacilli were observed for probiotic properties: Acid and bile salt tolerance, gelatinase activity, and autolytic activity. For analyzing the adhesive attributes, isolates were observed for autoaggregation, coaggregation and microbial adhesion to solvents assay. Results: About 12 Lactobacillus strains among 98 isolates exhibited maximum antimicrobial activity were further selected for identifying their probiotic and adhesive attributes. Among 12 selected isolates, cell-free supernatant (CFS) of buffalo milk BM10 and goat milk GM10 showed excellent antimicrobial activity, 20.34±0.02 mm against Staphylococcus aureus and 18.65±0.11 mm against Escherichia coli. Isolates showed survival at pH 2 and 3 and can tolerate 0.2-0.3% bile salt concentrations. The GM5 showed maximum autoaggregation (67.04±0.61%) and minimum coaggregation (11.51±0.50%) showed by GM3. The BM10 exhibited maximum adherent value 64.84±1.41% for n-hexadecane. Conclusion: The two lactobacilli, BM10 and GM10 identified as Lactobacillus fermentum and Lactobacillus pentosus on the basis of phenotypic and sugar utilization tests. The CFS of both lactobacilli can be used as antimicrobial agent. Both isolates showed significant results of probiotic and adhesive attributes, therefore, can be evaluated for clinical and therapeutic applications.