Role of 3-Nitropropanoic Acid in Nitrate Formation by Aspergillus flavus

Abstract

Aspergillus flavus formed nitrate, 3-nitropropanoic acid (3-NPA), Kojic acid, and a substance tentatively identified as N-formyl-N-hydroxyglycine during growth in a medium with ammonium as sole nitrogen source. The concentration of the nitro compound reached a maximum prior to the appearance of nitrate; the 3-NPA level subsequently decreased with a concomitant increase in nitrate concentration. Replacement cultures of A. flavus produced nitrate from culture filtrates containing 3-NPA or from synthetic 3-NPA but not when supplied with fresh ammonium-sucrose medium, the nitrate-nitrogen formed being equivalent to 50% of the quantity of the 3-NPA-nitrogen initially present. Neither nitrate nor 3-NPA was synthesized by the fungus during growth in media with low pH or low ammonium concentrations. It is proposed that 3-NPA is either an intermediate or is in equilibrium with an intermediate in nitrification by the fungus.