Screening of Lactobacillus plantarum isolated from fermented idli batter for probiotic properties

Abstract

Probiotics are defined as live microorganisms which when administered in adequate amounts confer a health benefit on the host. The objective of this study was to screen eight potential probiotic Lactobacillus plantarum strains from fermented idli batter using in vitro assays such as bile tolerance, acid tolerance, transit tolerance in the upper human gastrointestinal tract, auto-aggregation, co-aggregation, hydrophobicity, susceptibility to various antibiotics, bile salt hydrolase assay, cholesterol assimilation and hemolysis. The isolates were able to tolerate up to 0.3% of bile for 4 to 6 h and pH 2.5, 3.5, 4.5, 6.5, 7.5 and 8.5. The isolates were able to resist growth against gastric and intestinal fluid. The auto-aggregation of the different L. plantarum strains ranged from 65 to 80% in all the isolates. The co-aggregation with pathogens like Listeria monocytogenes (MTCC 657) and Escherichia coli (MTCC 728) ranged from 51 to 64%, however, low levels of co-aggregation were observed in L. plantarum (MTCC 6161) and L. rhamnosus (MTCC 1408) ranging from 32 to 46% and hydrophobicity from 49 to 77%. The isolates showed resistance towards antibiotics like gentamycin, ciprofloxacin, nalidixic acid and norfloxacin. All the isolates showed bile salt hydrolase activity with cholesterol lowering capacity, the highest being 73% by L. plantarum JJ 18. The isolates possessed â-galactosidase activity exhibiting 322 to 1000 MU of enzyme activity. No isolates showed hemolysis activity. Thus, the different L. plantarum isolates exhibited probiotic potential which would attribute beneficial effect to mankind.

Key words: Lactobacillus plantarum, probiotics, cholesterol, β-galactosidase.