Mining, heterologous expression, purification and characterization of 14 novel bacteriocins from Lactobacillus rhamnosus LS-8.

Bacteriocins are a subclass of antibacterial peptides considered to be the most promising alternative to antibiotics. A large number of unknown bacteriocins are hidden in lactic acid bacteria. In this study, by combining the genome with LC-MS/MS, 14 novel bacteriocins produced by Lactobacillus rhamnosus LS-8 were detected. Moreover, these bacteriocins were successfully cloned via plasmid pET-28a(+) and pET-30a(+) and heterologously expressed in Escherichia coli BL21. Escherichia coli ATCC25922 and Staphylococcus aureus ATCC25923 were used to confirm their antibacterial activity. Subsequently, the four bacteriocins (pH 25, S68, S81, and S137) with the strongest antibacterial ability were selected, and their expression conditions were optimized. Purification was performed by cation exchange chromatography and high performance liquid chromatography, and the active parts were collected and analyzed by mass spectrometry. The mass spectrometry analysis revealed that peptide coverage was >71.39%. The MICs of the four bacteriocins against four pathogenic bacteria ranged from 5.38 to 19.84 μg/mL. In addition, these bacteriocins significantly inhibited the growth of four standard pathogenic bacteria. They also exhibited broad-spectrum bacteriostasis on Gram-positive and Gram-negative bacteria. Therefore, these new bacteriocins have great potential in the study of alternative antibiotics.