Definition and Examples of Lantibiotics
The term lantibiotics refers to antibacterial substances synthesized by particular lactic bacteria. These microorganisms produce antibiotics to prevent pathogens from settling in the same environment and steal their nourishment.
In the past, antibiotics with a broad spectrum of action have been studied and researched, therefore active against all bacterial species. However, a type of intervention of this type has favored the development of resistant bacterial strains. Hence the association of a lantibiotic with a antibitico enhances the effect of the latter and promotes a more rapid restoration of intestinal functions.
Lactic acid bacteria are capable of producing a broad spectrum of proteins and peptides which possess antimicrobial activity. The structure of these peptides varies between the essentially linear one, for example of bacteriocins, to the complex one of peptides, which can contain various rings through the formation of bridges with lanthionine (Lan) or b-methillantionine (Me-Lan) residues.
These bacteriocins are called LANTIBIOTICS and appear as an "interesting addition to" conventional "antimicrobials in a period in which resistance to antibiotics compromises their use.
In 1991 the group of lantibiotics was divided into two subgroups:
Type A: elongated and flexible molecules, positively charged. It seems that they act by depolarizing the cytoplasmic membrane, and thus favoring the formation of pores with the loss of essential constituents of the antagonist bacterial cell. Example of such lantibiotics: nisin.
Type B: are represented by molecules with a globular structure, negatively charged or electrically neutral. They interfere with the enzymatic reactions essential for the growth and survival of the target bacterium.
Type B lantibiotics include mersacidin and actagardine.
Application of lantibiotics
Some characteristics of lantibiotics make these compounds particularly interesting for their potential applications in both the food and biomedical sectors. Many of these peptides have a broad spectrum of activity and are relatively thermostable and resistant to proteolysis.
Lantibiotics can be added to foods in various ways:
1) a lantibiotic producing strain can be used as a starter culture or added to a fermented food.
2) a producer strain could be used as a protective culture on the surface of a food, to protect it from temperature variations induced by the growth of unwanted bacteria. They can therefore increase the shelf life of the food, ie its storage time.
3) the antibiotic can be added as a purified or concentrated compound; for example, nisin (E234) is still used today in melted and spreadable cheeses, pasteurized desserts, milk.
