ABSTRACT

Lactic acid bacteria isolated from ogiri and soymilk were screened to determine their antibacterial activity against food spoilage organisms. The antimicrobial activity of these probiotic bacteria against many species or microorganisms is one useful property they possess which could be useful to prevent food spoilage caused by certain sensitive bacteria and also to control the speed of propagation of potentially pathogenic bacteria by their application. Lactic acid bacteria are probiotic bacteria that produce metabolites with broader spectrum of activity. The antagonistic properties of these isolates against Escherichia coli, Staphylococcus aureus and Salmonella typhi were examined using agar well diffusion method. Two lactic acid bacterial isolates, namely C₁ and C₂ were identified as Lactobacillus plantarium and Lactobacillus brevis were effective against all the selected indicator organisms except  Salmonella typhi. Among the isolates C₁ which has a broader spectrum of activity showed the highest antibacterial activity, against all the indicator pathogens tested, except Salmonella typhi. Its activity was maximum against Escherichia coli with a zone of inhibition 12.0 mm diameter and least activity against S. typhi as well, with the diameter or inhibition 1.6 mm. Overall, the isolated lactic acid bacteria produced bacteroicin showed the remarkable but different inhibitory effects against both Gram negative and Gram positive pathogenic strains. This therefore suggests that these probiotic isolates could be used as a natural biopreservatives in different food products.