Lactic acid bacteria are non pathogenic organism widely distributed in nature typically involved in a large number of spontaneous food fermentation. The purpose of this study was to characterize the bacteriocinogenic lactobacilli from fermented idli batter which can find application in biopreservation and biomedicine. Eight most promising lactobacilli were chosen from twenty two isolates based on their spectrum of activity against other lactic acid bacteria and pathogens. The eight lactobacilli were characterized based on the various classical phenotypic tests, physiological tests and biochemical tests including various carbohydrate utilization profiles. All isolates were homo fermentative, catalase, and gelatin negative. Molecular characterization was performed by RAPD, 16S rRNA analysis, 16S ARDRA, and Multiplex PCR for species identification. RAPD was carried out using the primer R2 and M13. Five different clusters were obtained based on RAPD indicating strain level variation. 16S rRNA analysis showed 99 to 100% homology towards Lactobacillus plantarum. The restriction digestion pattern was similar for all the isolates with the restriction enzyme AluI. The subspecies were identified by performing Multiplex PCR using species specific primer. Among the five clusters, three clusters were clearly identified as Lactobacillus plantarum subsp. plantarum, Lactobacillus pentosus, and Lactobacillus plantarum subsp. argentoratensis.
Lactic acid bacteria are known to produce numerous antimicrobial compounds that are active against various pathogens. Here, we have purified and characterized a novel low-molecular-weight (LMW) antimicrobial compound produced by Lactobacillus and Pediococcus isolated from fermented idly and uttapam batter. The LMW compound was extracted from cell-free supernatant using ice-cold acetone, purified by gel permeation and hydrophobic interaction chromatography. It exhibited antimicrobial activity against Gram-positive and Gram-negative pathogenic bacteria sparing the probiotic strains like Lactobacillus rhamnosus. The molecular weight of the LMW compound was identified as 204 Da using LC-MS-ESI. In addition, the structure of the compound was predicted using spectroscopic methods like FTIR and NMR and identified as 2-hydroxyl indole-3-propanamide. The LMW compound was differentiated from its related compound, tryptophan, by Salkowski reaction and thin-layer chromatography. This novel LMW compound, 2-hydroxyl indole-3-propanamide, may have an effective application as an antibiotic which can spare prevailing probiotic organisms but target only the pathogenic strains.
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