Cultural conditions for the production of bacteriocin by a native isolate of Lactobacillus delbruecki ssp. bulgaricus CFR 2028 in milk medium.

The effect of growth parameters and the molecular basis for antibacterial activity by a natural isolate of Lactobacillus delbruecki ssp. bulgaricus CFR 2028 was studied. The inhibition was tested against a toxigenic strain of Bacillus cereus F 4810. When grown in milk medium, the activity was highest at an incubation temperature of 37 degrees C in 48 h. The antibacterial activity appeared to be produced between late logarithmic and early stationary phases. The active principle was proteinaceous in nature (bacteriocin) and stable to low pH (3.8-5.0) and heat (75 degrees C for 30 min). There was also the possible role of hydrogen peroxide in bringing about inhibition. The strain of Lact. delbruecki ssp. bulgaricus CFR 2028 revealed the presence of plasmid DNA bands of 9.4 and 6.5 kbp, respectively, in agarose gel electrophoresis. The above strain has the potential to be used as a biopreservative in popular Indian fermented foods.