Abstract
Bacteriocins are ribosomally produced, proteinaceous antimicrobial biomolecules with versatile functions and are considered potential next-generation therapeutics. They are secreted by a few groups of lactic acid bacteria (LAB) that possess the ability to combat spoilage and foodborne pathogens. Given these properties, bacteriocins have generated significant interest for their potential use as natural food preservatives. This study aimed to isolate and characterize bacteriocin-producing LAB with potent antimicrobial properties and evaluate their potential use as natural food preservatives and alternative therapeutics. A total of 47 morphologically distinct LAB isolates were screened for antibacterial activity against foodborne pathogens. The isolate exhibiting the strongest antimicrobial activity, designated CW40, was selected for further study. The bacteriocin was purified from the culture supernatant using gel filtration chromatography. The isolate was identified by 16S rDNA sequencing, and optimal conditions for bacteriocin production were determined. The molecular weight of the bacteriocin was estimated, and its antimicrobial spectrum, enzyme sensitivity, bile salt tolerance, and antibiotic resistance profile were assessed. Isolate CW40 produced 8 kDa (MW) of bacteriocin from the purified supernatant of its grown culture and was identified as Lactobacillus rhamnosus through 16S rDNA sequencing. The bacteriocin production of L. rhamnosus was optimized, with maximum yield observed at 37℃ with pH 7. The bacteriocin exhibited strong antimicrobial activity against Bacillus subtilis, Bacillus cereus, and Escherichia coli. Protease treatment eliminated antimicrobial activity, confirming the proteinaceous nature of the bacteriocin. Maximum bacteriocin activity at 4,098 AU/mL was observed against E. coli. The strain tolerated up to 0.3% (w/v) ox gall and demonstrated a broad antibiotic resistance. The results highlight Lactobacillus rhamnosus CW40 as a promising source of bacteriocins with potent antimicrobial properties. These findings support the potential application of CW40-derived bacteriocins as natural biopreservatives and adjunct therapeutic agents in combating foodborne pathogens and antibiotic-resistant infections.