| Bacteriocins, ribosomally synthesized proteinaceous antibacterial substances produced by bacteria, represent an alternative against the rapid increase in bacterial antibiotic resistance. Lantibiotics, a class of bacteriocin, are antibiotic peptides which contain modified amino acids obtained by posttranslationnal modifications. Bacteriocins produces by Streptococcus mutans are called mutacins. The strain S. mutans 29B produces mutacin H-29B. Production of mutacin H-29B was obtained in supplemented wey permeate. Production rate, evaluated by critical dilution method, was partially improved by adding lactose or sucrose as carbon source to the medium. Crude mutacin H-29B showed resistance to heat (100°C, 1 h) and autoclaving (121°C, 15 min). Its activity was preserved at acid pH but inhibited by basic pH. Mutacin H-29B was purified by succesive hydrophobic chromatographies. Molecular mass of the peptide was determined by mass spectrometry and evaluated at 3246.08 +/- 0.1 Da. Amino acids sequence was obtained by Edman degradation after derivatization of the peptide with alkaline ethanethiol. Twenty-four amino acids were identified, four of which were modified. Amino acids sequence of mutacin H-29B is similar to that of mutacin II produced by S. mutans T8. Efficiency of mutacin H-29B was compared to the ]antibiotics mutacin B-Ny266 and nisin A, and to the antibiotics oxacillin and vancomycin, against food and clinical pathogenic strains of Listeria monocytogenes and Staphylococcus aureus. Mutacin H-29B was more active than nisin A and oxacillin, as active as mutacin B-Ny266 but less active than vancomycin against the pathogenic strains tested. |
