Purification, amino acid sequence, and characterization of bacteriocin GA15, a novel class IIa bacteriocin secreted by Lactiplantibacillus plantarum GCNRC_GA15

The bacteriocins produced by lactic acid bacteria (LAB) are attracting attention due to their promising applications in food and pharmaceuticals fields. Hence, a LAB strain, GCNRC_GA15, was isolated from Egyptian goat cheese, and molecularly identified as Lactiplantibacillus plantarum. This strain showed a wide antimicrobial spectrum, which was found to be of proteineous nature, suggesting that L. plantarum GCNRC_GA15 is a bacteriocin-producer. This bacteriocin (bacteriocin GA15) was partially purified using cation exchange, and hydrophobic interaction chromatography. Tricine SDS-PAGE analysis for the fraction showing bacteriocin activity has estimated the molecular mass to be 4369 Da. Furthermore, amino acid sequencing of this peptide has detected 34 amino acids, and comparing its amino acid sequence with those of some pediocin-like bacteriocins revealed that bacteriocin GA15 has the conserved sequence (YYGNGV/L) in its N-terminal region which identified bacteriocin GA15 as a pediocin-like bacteriocin. Bacteriocin GA15 showed good heat and pH stabilities, and its activity was enhanced after treatment with Tween 80 or Triton X-100. Bacteriocin production medium was statistically optimized using the Plackett-Burman and Central Composite designs. As a result, bacteriocin production increased from 800 to 12,800 AU/ml using the optimized medium in comparison with result recorded for the un-optimized medium.