P-Factor,a New Peptidic Growth Factor for Pediococcus soyae

The P-factor a new growth factor for Ped. soyae, is found in partial acid and enzymic hydrolysates of Hammersten’s milk casein, and is therefore, supposed to be a kind of peptide. The well-known peptidic growth promoting substance for Lact. casei, strepogenin and its relating substances, are quite ineffective to the author’s organism. P-factor exists along with the S-factor which is another growth promoting-factor for this lactic acid bacterium, in soy mash juice and in the water extract of Aspergillus sojae mycelium. The former substance is also found in various kinds of commercial peptones. The factor was not substitutable with all of the 19 synthetic peptides tested. S-factor is effective, only in the presence of the P-factor.