Antibacterial activity of bacteriocin extracted from Lactobacillus plantarum isolated from fermented rice-water milk extract against selected pathogenic bacteria

Abstract

Bacteriocin are produced by lactic acid bacteria during their primary growth phase as natural antimicrobial agents against closely or distantly related microorganisms in their natural environment. This study aimed at ascertaining the inhibitory effect of bacteriocin extracted from Lactobacillus strains, against Staphylococcus aureus, Klebsiella pneumoniae and Escherichia coli. Lactobacillus sp. was isolated from rice water samples utilizing the de Mann, Rogosa and Sharpe (MRS) agar, and subsequently, the MRS broth. The isolates were morphologically and biochemically identified, then further confirmed to be Lactobacillus plantarum strains using the 16S rRNA gene sequence analysis. Chloroform solvent precipitation was carried out to extract the bacteriocin from the MRS broth culture. The bacteriocin from Lactobacillus plantarum 1 (RW1) displayed high inhibitory activity against the Gram-negative bacteria at 5-13mm, as compared to 9mm for the Gram-positive bacteria. The Lactobacillus plantarum 2 (RW2) bacteriocin displayed the highest activity against both the Gram-negative bacteria and the Gram-positive bacteria at 14mm and 10mm respectively. Characterization of the bacterial isolates using the 16SrRNA gene sequence analysis revealed the isolates to be Lactobacillus plantarum strain LL441 and Lactobacillus plantarum strain C11. In conclusion, the chloroform extracted bacteriocin produced from Lactobacillus plantarum isolated from new sources, displayed antibacterial activity and could serve as bio-preservatives against pathogens in food and the food industries.