Purification and characterization of antimicrobial peptides from fish isolate Carnobacterium maltaromaticum C2: Carnobacteriocin X and carnolysins A1 and A2

• Carnobacteriocins BM1, B1, and a B2 variant are produced by Carnobacterium maltaromaticum C2.
• We herein report the first isolation of the previously predicted carnobacteriocin X.
• C. maltaromaticum C2 also produces a novel two-component lantibiotic homologous to enterococcal cytolysin.

Carnobacterium maltaromaticum C2, isolated from Brazilian smoked fish (Surubim, Pseudoplatystoma sp.), was found to exert antimicrobial activity against Listeria monocytogenes, an important foodborne pathogen. In this study, the bacteriocins produced by C. maltaromaticum C2 were purified via an extraction with XAD-16 resin, a C18 solid phase extraction, followed by reversed-phase fast protein liquid chromatography. The purified active fractions were characterized using tandem mass spectrometry, permitting the identification of multiple bacteriocins. Carnobacteriocins BM1, B1, and a variant of carnobacteriocin B2 were all found, providing much of the antilisterial activity. Additionally, we herein report the first isolation of the previously predicted antimicrobial peptide carnobacteriocin X. Moreover, C. maltaromaticum C2 produces a novel two-component lantibiotic, termed carnolysin, homologous to enterococcal cytolysin. This lantibiotic is antimicrobially inactive when tested against the non-bacteriocinogenic strain C. maltaromaticum A9b −, likely requiring an additional proteolytic cleavage to reach maturity.