Diversity in the antibacterial potential of probiotic cultures Bacillus licheniformis MCC2514 and Bacillus licheniformis MCC2512

The aim of the present study was to investigate the characteristic diversity and stability of antimicrobial compounds produced by two
probiotic strains of Bacillus licheniformis (MCC2514 and MCC2512). Antimicrobial compounds from the two strains notably varied, related to
stability and potency. The inhibitory spectrum of B. licheniformis MCC2512 was higher than MCC2514, but, related to the effect on Micro-
coccus luteus ATCC9341, MCC2514 (LD50 ¼ 450 AU ml�1) was more potent than MCC2512 (LD50 ¼ 750 AU ml�1). The compounds were
thermo-resistant and stable at a wide range of pH and exhibited considerable resistance to digestive enzymes and bile salts (anionic biological
detergents), contributing to their appropriate application in various food systems. The isolate B. licheniformis MCC2512 gave a positive response
to Bacillus subtilis-based biosensors BSF2470 and BS168.BS2, confirming the mode of action on the cell wall and subtilin-type, respectively.
For B. licheniformis MCC2514, the mode of action was characterized by constructing B. subtilis reporters that interfered in five major
biosynthetic pathways, i.e., biosynthesis of DNA, RNA, protein, the cell wall and fatty acids. B. licheniformis MCC2514 responded to the yvgS
reporter, indicating it as an RNA synthesis inhibitor. Overall, the investigation reveals variability of the antimicrobial compounds from B.
licheniformis of different origins and for their possible application as biopreservative agents.