Bacteriocins, growth inhibitory substances, of lactic acid bacteria

Lactic acid bacteria have been traditionally used for the fermentation of foods and beverages because of their contribution to flavor and aroma development and to spoilage retardation. The preservative effect of lactic acid bacteria during the manufacture and subsequent storage of fermented foods is mainly due to the acidic conditions that they create in converting carbohydrates to organic acids (lactic acid and acetic acid) in the food during their development. Recently, it has become clear that lactic acid bacteria can produce and excrete inhibitory substances, such as hydrogen peroxide, diacetyl, and bacteriocins, in addition to organic acids. Bacteriocins can be biologically active proteins or protein complexes displaying a bactericidal mode of action towards Gram-positive bacteria, and particularly towards closely related species. Because bacteriocins are degraded and inactivated in the human alimentary canal and lactic acid bacteria have been used in foods since ancient times, bacteriocins are used as natural food preservatives. As such, they have been the subject of a considerable amount of research. We outline here recent studies on bacteriocins, mainly nisin produced by Lactococcus lactis subsp. lactis.