Résumé
Lactobacillus bulgaricus is one of the predominant lactic acid bacteria of dahi, conferring technological and functional attributes. In the present study thirty dahi samples were investigated for bacteriocin producing L. bulgaricus. Fourteen different isolates were obtained and five were scrutinized for antibacterial activities against food born pathogens. Amongst, a strain TLB06FT was found to have a wide array of antibacterial activities against Gram positive and negative bacteria was selected for further characterization. Growth media optimization for this strain revealed maximum bacteriocin production on MRS media supplemented with glucose [2%], sodium chloride [1%], Tween-80 [0.5%] and yeast extract [1%]. In addition, optimization of growth conditions revealed maximum bacteriocin production at pH 5.5 and temperature of 30-37[degree]C. Bacteriocin showed thermo stability at 90[degree]C and remained highly active in the pH range of 3.5-7.5, inactive by protein catalyzing enzymes and showed no change in activity [800AUmL[-1]] when treated with organic solvents and surfactants. The obtained bacteriocin was purified to 1600AU mL[-1] by ammonium sulfate precipitation [80%] by using dialyzing tubing. In the same way, a single peak was obtained by RP-HPLC having antibacterial activity of 6400AU mL[-1]. Thus, wild strains of L. bulgaricus have great potential for the production new and novel type of bacteriocins