Biotechnological potential and in vitro safety assessment of Lactobacillus curvatus BCS35, a multibacteriocinogenic strain isolated from dry-salted cod (Gadus morhua)

The antimicrobial activity of Lactobacillus curvatus BCS35 is due to the production of, at least, two class Ha bacteriocins: sakacin P-H12Y (SakP-H12Y), which is a sakacin P (SakP) variant with tyrosine (Tyr) instead of histidine (His) at position 12, and sakacin X (SakX). Moreover, DNA sequence analysis revealed the presence of the genes encoding the two-peptide bacteriocin sakacin T. In order to compare the specific antimicrobial activities of SakP-H12Y and SakX with other class Ha bacteriocins (SakP from Lactobacillus sakei LTH673 and pediocin PA-1 (PedPA-1) from Pediococcus acidilactici 347), and to determine if the substitution His12/Tyr12 in SakP-H12Y/SakP exerts any effect on the bacteriocin potency and/or specificity, these four bacteriocins were purified and challenged against different indicator strains. Our results showed that (i) PedPA-1 was, in general, the most active peptide, and (ii) SakP-H12Y, which contains one less positively charged residue in the N-terminal half (His12/Tyr12), has a reduced antimicrobial potency against most of the tested indicators compared to Sale, confirming the importance of the N-terminal cationic patch of SakP-H12Y/SakP in target-cell binding, potency and specificity. The in vitro safety of Lb. curvatus BCS35 was established by antibiotic susceptibility testing concluding that it may be considered as a safe strain.