NEGATIVE EFFECT OF AMMONIUM-NITRATE AS NITROGEN-SOURCE ON THE PRODUCTION OF WATER-SOLUBLE RED PIGMENTS BY MONASCUS SP

Ammonium salts, especially ammonium nitrate, have been used as nitroge n sources for production of traditional water-insoluble Monascus pigme nts. However, we noted that defined media employing NH4NO3 as the sole nitrogen source in fermentations supported only poor pigment producti on by Monascus sp., and the pigments produced were mainly cell-bound. NH4NO3 was found not to (a) repress pigment synthase formation, (b) en hance synthase decay, or (c) serve as a nitrogen source for pigment pr oduction by resting cells; it had a weak inhibitory effect on the acti on of pigment synthase(s). The high level of cell-bound pigments accum ulated in NH4NO3-grown cells did not exert a feedback effect on the fu rther synthesis of pigments. These observations indicate that the reas on why NH4NO3 supports only low pigment production during fermentation s is the poor ability of NH4NO3 to donate nitrogen in the Schiff-base reaction converting-orange pigments to red ones.