INFLUENCE OF DIFFERENT VITAMIN-NITROGEN SOURCES ON CELL-GROWTH AND PROPIONIC-ACID PRODUCTION FROM SUCROSE BY PROPIONIBACTERIUM-SHERMANII

Cell growth and organic acid production by Propionibacteria are depend ent on the vitamin-nitrogen source in the culture medium. Final cell a nd propionic acid concentrations produced by Propionibacterium sherman ii, using corn-steep liquor, were higher than those obtained utilizing yeast extracts. Since corn-steep liquor is much cheaper than yeast ex tract, the process becomes more attractive. By calculating the specifi c growth rates, it was observed that the critical propionic acid conce ntration, that prevents all growth (mu(X) = 0), is different depending on the vitamin-nitrogen source used and its concentration. For exampl e, for 5.0 and 15.0 g/l Oxoid yeast extract, those critical propionic acid concentrations were 16.0 and 27.0 g/l, respectively. Such propion ic acid concentrations inhibit the cell growth, but not the formation of acid. The specific propionic acid production rate also indicates th at the critical concentration for metabolic activity, when propionic a cid is no longer produced (mu(P) = 0), varies according to the vitamin -nitrogen source and its concentration in the medium. For 5.0 and 15.0 g/l Oxoid yeast extract, those concentrations were 22.1 and 30.1 g/l, respectively.