Identification and in vitro evaluation of probiotic attributes of lactic acid bacteria isolated from fermented food sources.

Consumer's vigilance towards health-promoting foods beyond only taste and nutrition has increased the recognition for probiotic products. In the present study, various parameters have been studied to define the probiotic properties of cultures isolated from different fermented products. Around 118 samples were selectively screened for antimicrobial compound (AMC) producing isolates by overlay-plate assay using Micrococcus luteus ATCC9341. Among 134 zone producing isolates, 48 cultures showing Gram-positive, catalase negative, non-spore forming and non-motile rods and cocci were selected. Subsequently, 18 strains were chosen based on non-hemolytic, absence of biogenic amine production, gelatinase and lecithinase negative trait for safer isolates. These were identified by biochemical assays and then subjected to RAPD-PCR. The selected cultures DB-1aa, DB-b2-15b, Cu2-PM7, Cu3-PM8 and IB-pM15 were identified by 16S rDNA sequencing as Enterococcus durans, Enterococcus faecium, Lactobacillus plantarum, and two Lactobacillus fermentum, respectively. Several in vitro experiments were carried out including acid and bile tolerance, survival under simulated gastrointestinal condition, adhesion assay to evaluate the probiotic potential of the isolates. In addition, the isolates were studied for competent properties such as antibacterial, antioxidant activity, and enzyme production for their functional application. The results of the study prove the efficiency of selected isolates as potential probiotic cultures and hence can be recommended for application in any functional food formulations.