A class III bacteriocin with broad-spectrum antibacterial activity from Lactobacillus acidophilus NX2-6 and its preservation in milk and cheese

A novel class III bacteriocin gene (NX371) was mined by bioinformatic analysis from Lactobacillus acidophilus NX2-6, which had 98.15% homology of helveticin J (GenBank: ARF21596.1) from Lactobacillus. helveticus R0052. Then the bacteriocin NX371 (37.1 kDa) was expressed in Escherichia coli, purified and refolded to investigate its stability and antimicrobial characteristics. It displayed dramatic antimicrobial activity against both Grampositive and Gram-negative foodborne pathogens, including Salmonella, Yersinia, Listeria, Enterobacter, Shigella, Escherichia, Staphylococcus, and Vibrio, which killed bacteria by weakening their cell wall, increasing the permeability of the membrane, and causing leakage of intracellular ATP. Furthermore, it showed a more extensive range of pH stability (3.0-8.0) than nisin and used to control the growth of pathogens in artificially contaminated milk and Mozzarella cheese (S. enteritidis, L. monocytogenes, E. coli, and S. aureus) at 25 and 35 degrees C, respectively. The number of bacteria in milk and cheese was reduced by 3.5-4.0 CFU/mL and 5.0-7.0 log CFU/g in the presence of 2.0 MIC90 NX371, respectively. Taken together, NX371 showed a broad spectrum of antimicrobial activities with significant thermal and pH stability, suggesting that it could be applied potentially in the dairy industry to control the foodborne pathogens.

Automated summary

A novel class III bacteriocin gene, NX371, was identified and expressed from Lactobacillus acidophilus with significant antimicrobial activity against various foodborne pathogens. The study demonstrated that NX371 exhibited thermal and pH stability, effectively inhibiting the growth of pathogens in milk and cheese.