Isolation and Characterization of Bacteriocin Producing Lactic Acid Bacteria from Fermented Foods

Bacteriocins are proteins produced by bacteria which inhibit the growth of similar or closely related bacterial strains. Lactic acid bacteria (LAB) which are predominantly present in the fermented foods are well known for producing bacteriocins. In the present study, five different fermented food samples, viz., green gram batter, curd, idly batter, dosa batter, and paneer were used for isolation of lactic acid bacteria. The organisms isolated were identified as Lactobacillus casei, Lactobacillus delbruckii and Streptococcus spp by biochemical characterization. The bacteriocins produced by these organisms inhibited the growth of the Bacillus subtilis, Pseudomonas aeruginosa, Escherichia coli, but there was no effect on the Proteus vulgaris and Staphylococcus aureus. Bacteriocins produced by the Streptococcus spp isolated from green gram batter were stable at pH 2 and pH 8. Exposure to UV light for 4 min had no effect on bacteriocin activity. The bacteriocins produced by L. casei (from idly batter) and Streptococcus spp (from dosa batter) retained their antagonistic property even at 100 °C against B. subtilis and P. aeruginosa. All bacteriocins were stable for a period of 15 days at 27 °C. The study revealed the use of bacteriocins as an antibacterial agent and their use in biological preservation of foods. Keywords: Bacteriocin, lactic acid bacteria, fermented foods