Research progress in proteolysis system of lactic acid bacteria and related gene expression

The proteolytic system of lactic acid bacteria which hydrolyzes exogenous protein into free amino acid were consists of extracellular peptidases, the peptide transport systems and a variety of intracellular peptidases. That makes up of the deficiency that lactic acid bacteria can not directly use inorganic nitrogen and protein. Therefore the proteolytic system has very important significance for the normal growth of lactic acid bacteria. Currently some scientists use the modern molecular techniques to study the gene expression levels of the key proteolytic enzymes of the different strains or the strains after different treatments in order to screen out the strains in which the genes of proteinases has high expression level and obtain the high-quality starter lactic acid bacteria strains.The proteolytic system of lactic acid bacteria and the advances in the expression level of genes related to the proteolytic system of lactic acid bacteria were reviewed in this paper with the hope of providing reference materials for the further study on protein metabolism of lactic acid bacteria.