CHARACTERIZATION OF BACTERIOCIN PRODUCED BY Lactobacillus sp. ISOLATED FROM NUNU AND ITS ANTIMICROBIAL PROPERTIES ON Escherichia coli

This Research focused on the isolation and characterization of bacteriocin produced by Lactobacillus sp. isolated from nunu, a traditionally fermented milk beverage, and its antimicrobial effect against Escherichia coli. Samples of nunu were collected from local markets in Oredo Local Government Area, Edo State, and analyzed in the Department of Science Laboratory Technology Microbiology Laboratory. The isolate was cultured on de Man, Rogosa, and Sharpe (MRS) agar and identified through morphological and biochemical characterization. The isolates were Gram-positive, catalase-negative, and capable of fermenting lactose, galactose, and fructose, confirming them as Lactobacillus sp.. Bacteriocin production was screened using the agar well diffusion method, with E. coli as the test organism. Clear zones of inhibition (ZOI) were observed, indicating the production of antimicrobial compounds. The bacteriocin extract was neutralized to pH 7.41 to eliminate the effects of organic acids and partially purified using ammonium sulfate precipitation (60% saturation) followed by dialysis. The purified extract was further characterized using High- Performance Liquid Chromatography (HPLC), which revealed distinct peaks corresponding to bacteriocin fractions. The antimicrobial assay showed that the bacteriocin exhibited inhibitory activity against E. coli, suggesting its potential as a natural bio preservative in perishable food products such as tomato. The findings indicate that bacteriocin from Lactobacillus sp. in nunu can serve as safe and effective alternatives to chemical preservatives and synthetic antibiotics, thereby contributing to improved food safety and public health.