Preliminary characterisation of bacteriocin produced by Lactobacillus acidophilus TS1 isolated from traditional dahi

Antimicrobial activity of 79 strains of Lactobacillus isolated from indigenous dahi were tested against the indicator strains of food pathogens (Escherichia coli, Streptococcus faecalis, Staphylococcus aureus, Salmonella typhi). Among these only eleven isolates produced inhibition zones of variable size against indicator microorganisms. Later on, only one strain of Lactobacillus acidophilus (TS1) was found to produce a wider zone of inhibition against all indicator microorganisms. The antimicrobial activity of this strain was inactivated by the proteolytic enzyme proteinase K and trypsin but not by alpha-amylase and lipase thus confirming its proteinaceous nature. It also showed a wide range of thermostability from 70-121 degrees C for 15 min and retained their antimicrobial activity over a wide range of pH (3-10). The addition of bacteriocin to the earlier growth phase showed pronounced inhibition against E. coli, and Streptococcus faecalis, as compared to Staphylococcus aureus, and Salmonella typhi. The molecular weight of the substance was in the range of 7.5 kDa. This result suggested that bacteriocin might be useful as a biopreservative in different food commodities.