Expression profiles of milk proteolysis-related genes in Lactobacillus paracasei EG9, a non-starter lactic acid bacterial strain, during Gouda-type cheese ripening

Abstract We investigated the expression profiles of proteolysis-related genes in Lactobacillus paracasei EG9, a non-starter lactic acid bacterial strain used as an adjunct starter in Gouda-type cheese production. The amino acid sequences of previously reported proteolytic enzymes in lactic acid bacteria were matched against the EG9 genome by translated BLAST search, and 31 candidate genes, including those coding for peptidases, oligopeptide transporters, and cell-envelope proteinases, were listed. The relative expression levels of these genes were evaluated at 0 and 30 days of cheese ripening. On day 0, 27 genes showed significantly up-regulated expression compared with the genes in the stationary phase of the reference cultured cells. On day 30, 25 genes were found to be significantly down-regulated. Our findings suggest that the proteolysis-related genes in EG9 play an important role in the proteolytic process from casein degradation through peptide uptake to free amino acid production during cheesemaking.