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Lactic acid bacteria (LAB) can produce antimicrobial substances with capacity to inhibit the growth
of pathogenic and spoilage microorganisms in foods. The preservative ability of LAB in foods is
attributed to the production of antimicrobial metabolites including organic acids and bacteriocins.
The present investigation was planned to isolate LAB from rhizosphere soil samples and to check the
antibacterial activity of bacteriocin at different temperature, pH and at different incubation periods
against different bacteria. 12 different isolates of Lactobacillus sp. were identified on the basis of
various morphological, cultural and biochemical characters and bacteriocins obtained from these
isolates were then checked for their antibacterial potential against different bacteria viz.,
Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. Bacteriocin produced from
isolate LB 12 showed maximum antibacterial activity against E.coli followed by S. aureus and P.
aeruginosa, thus isolate LB 12 was considered for further study. Temperature affected the
antibacterial activity of bacteriocin and it was observed that the bacteriocin showed highest zone of
inhibition at 60°C against E.coli, S.aureus and P. aeruginosa (26, 24 and 23 mm respectively) and
least activity was observed at 121°C. Antibacterial activity of bacteriocin was retained at pH 2-10
but maximum activity was observed at pH 6 against E.coli, S.aureus and P. aeruginosa (24, 22 and
18mm) and incubation period of 24 hrs at 37⁰C was observed to be the most suitable for bacteriocin
activity against test bacteria. Behavior of bacteriocin produced by isolated strains in the present
investigation was considered as bacteriocidal.
Keywords: Lactic acid bacteria, Rhizosphere soil, Antibacterial activity, Bacteriocin