From casein to cheese: The role of Lactococcus lactis

Lactococci have limited biosynthetic abilities. In addition to the energy sources many solutes have to be taken up. Essential and non-essential amino acids are accumulated via specific transport systems. The concentration of these solutes in milk is insufficient to support optimal growth. Cells secrete proteinases and peptidases to hydrolyse casein. During milk fermentation, the growth requirements of lactococci are satisfied by the peptides and amino acids released upon casein degradation. When present in limiting amounts. amino acids are acquired by uptake and subsequent hydrolysis of peptides. The effects of an imbalance of the supply of amino acids on the growth and metsbolic activities of these bacteria are discussed.