Stimulation of Lactic Acid Bacteria by Substances Concomitant to Certain Proteolytic Enzymes

The addition of certain protein hydrolytic products to semi-synthetic and synthetic media has led to observations of enhanced growth and/or metabolic activity of a number of bacterial genera. A classic study in this phase of bacterial nutrition was that of Woolley and his associates, who used the term "strepogenin" to denote the growth-stimulatory effect of various peptides. They observed that trypsinized casein (8) and acid hydrolyzed casein (9) contained hydrolytic cleavage products (presumably peptides) that markedly increased the growth response of several genera of lactic acid bacteria. Subsequent investigations failed to elucidate the structure of the active peptides in casein hydrolyzates; however, certain synthetic peptides containing glutamic acid exhibited activity, although this activity was much less than that of hydrolyzed casein (11).