Isolation of lactic acid bacteria and their antibacterial spectrum against gram positive and gram negative bacteria

Hundred and eighteen Lactic acid bacteria were isolated from indigenous sources including milk, yogurt, vegetables, meat, fermented dough and infant feces. On screening these isolates by stab and agar well method, were found them to produce antimicrobial substances inhibitory against other LAB strains. They also exhibited a broad spectrum of antagonistic activity against gram negative i.e E. coli, S. typhi, S. dysenterae, K. pneumonia and P. vulgaris and gram positive pathogens i.e S. pyogenes, S. fecalis, S. pneumonae, S. aureus, B. subtilis, B. cereus and C. diphtherae. Only 23 amongst these elaborated bacteriocin like inhibitory substance (BLIS) while the rest showed antagonism mainly due to organic acids. One of the strongest BLIS producing strain of lactobacillus LBT-36 isolated from fermented tomatoes was partially purified by ammonium sulphate precipitation and the purified protein was subjected to SDS-PAGE which gave a single band. Therefore, these strains after further essential investigations could be selected as good candidates for commercial use as bio-presevatives and can also contribute in improving human health by using them as Probiotics in different foods.