Lactic acid bacteria are known probiotics that produce bacteriocin peptide compounds during their primary growth phase as natural antimicrobial agents against closely or distantly related microorganisms in their natural environment. The purpose of this study was to ascertain the inhibitory effect of bacteriocin compounds extracted from lactic acid bacteria in fermented rice water-milk extract using chloroform solvent, against the test pathogenic bacteria used (Staphylococcus aureus, Klebsiella pneumonia and Escherichia coli). From the rice water samples, two morphologically and biochemically confirmed Lactobacillus plantarum strains were isolated utilizing the de Mann, Rogosa and Sharpe (MRS) agar. Chloroform precipitation was used to extract the bacteriocin from the M.R.S culture broth. The bacteriocin extracted from Lactobacillus plantarum strain 1 (RW1) displayed a broad spectrum of activity against the Grampositive and Gramnegative bacteria within a 9-13mm range, whereas the Lactobacillus plantarum strain 2 (RW2) showed a narrow spectrum of activity against both bacteria types at 5-14mm for the Gramnegative bacteria and at 10mm for the Grampositive bacteria, and in addition, had the most growth inhibition against the Gramnegative bacteria at 14mm respectively. The NCBI nucleotide BLAST sequence and phylogenetic tree analysis revealed the bacteria strains as Lactobacillus plantarum strain LL441 and Lactobacillus plantarum strain C11. In conclusion, the study demonstrates the potential of bacteriocin extracts in inhibiting the growth of pathogenic bacteria from environmental samples.

Keywords: Lactic acid bacteria, Bacteriocin, Rice water extract, Chloroform precipitation, Grampositive bacetria, Gramnegative bacteria, broad spectrum, narrow spectrum.