Peptides utilization by lactic acid bacteria

Abstract

The conversion of peptides to free amino acids and their subsequent utilization by lactic acid bacteria (LAB) is essential to sustain an optimal growth in natural media. Peptides utilization requires the concerted action of a peptidase(s) (such as aminopeptidases, dipeptidases and carboxypeptidases) and a transport system(s). Both biochemical and genetics approaches strongly suggest an intracellular location of all peptidases characterized to date. At the present in LAB have been characterized different peptide transport systems to uptake oligopeptides, di and tri peptides. Peptides supply the essential amino acid requirements of LAB from different ecological niche as milk, wine, meat. In general bacterial growth yield is higher in the presence of nitrogen from peptides than that from free amino acids. The contribution of nitrogen source to the growth of strains of Lactococcus lactis in milk is supported about 90% by casein-derived peptides. The growth of LAB from wine occurs with higher maximal growth rate in chemically defined media containing a peptide as only source of an essential amino acid than in the presence of the corresponding free amino acid. However in some strains of LAB the growth rate values obtained in chemical defined media with dipeptides is the same as in amino acid containing media. In a strain of Oenococcus oeni the dipeptide glycyl-glycine in the synthetic medium was consumed to a greater extent than the free amino acid. The higher Gly-Gly utilization significantly increased the glycine released outside the cell and the microorganism could employ it as an exchange mechanism for the incorporation of other amino acids such as alanine favoring its growth under poor nutritional conditions.