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Growth responses of Brevibadterium ammoniagenes BA 17-2, which had been obtained by the treatment of several mutagens in our previous report, were investigated to select the preliminary optimal concentrations of phosphate, Mg^(++), Mn^(++) and thiamine for the production of 5´-XMP aminase. In this experiment it was shown that the concentration of phosphate in the medium has an important effect on the growth of microorganism. Using the medium containing 0.2% of MgSO₄·7H₂O, 3㎎/ℓ of MnSO₄·H₂O, and 1㎎/ℓ of thiamine-HCl, the maximum cell mass was obtained at the concentration of 0.4% of KH₂PO₄ and KH₂PO₄, respectively. Above the concentration of these phosphates, cell growth was inhibited as the phosphate concentration increased to 1?0, but the inhibition was overcome by the addition of 1% of MgSO₄·7H₂O and 3㎎/ℓ of thiamine-HCl. The 5´-XMP aminase activity was also influenced by the concentration of phosphate, Mg^(++), Mn^(++), and thiamine. In addition, the optimal culture pH and temperature for the enzyme activity were found to be 6.8 and 32℃, respectively.
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