International Journal of Fermented Foods

In the present study, out of 14 strains, only four strains were found to harbour plasmid. They were of more than 7kb in size. Plasmid loss in strains i.e. Lactobacillus paracasei ND11, Lactobacillus rhamnosusNS4, Lactobacillus bulgaricus 009 & Lactobacillus rhamnosus I4 was obtained by curing experiments (growth) in the presence of curing agent novobiocin. Plasmid curing resulted in loss of their ability to produce bacteriocin as established by the absence of the inhibitory activity against indicator organisms. Partially purified bacteriocin from Lactobacillus paracasei ND11 was found to be a protein entity through SDS-PAGE with an approximate molecular weight of 4.3kDa. The bacteriocin was found sensitive to proteolytic enzymes and stable over wide range of temperatures (25 to 55^°C) and pH (5–8). Crude bacteriocin was used for biopreservation of paneer (acid coagulated dairy product) samples stored at 25°C for 7 days and found to reduce total counts, coliforms as well as yeast and molds counts significantly. However, these are novel bacteriocin producing cultures and could be utilized for biopreservation of dairy foods.