NITRIFICATION BY GROWING AND REPLACEMENT CULTURES OF ASPERGILLUS

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Abstract
Growing cultures of Aspergillus Jiuvus converted a variety of amino acids, propionamide, malonylmonohydroxamate, 3-nitropropionate (3-NPA), and nitrite to nitrate. Nitrate production was particularly high with L-asparagine and 3-NPA, half the nitrogen of the latter being recovered as nitrate. Many other compounds either failed to enhance or inhibited nitrification. Replacement cultures of the fungus oxidized half the nitrogen of β-alanine or aspartate to nitrate, but ammonium, hydruxylamine, nitrite, or a variety of organic nitrogenous compounds were not nitrified by the hyphal mats. The ability of the fungus to nitrify β-alanine and aspartate but not 3-NPA was lost if the organism was maintained on artificial media. A number of aspergilli excreted nitrate during growth in media containing ammonium or β-alanine. Replacement cultures of the aspergilli did not oxidize ammonium, but most of the fungi produced nitrate from 3-NPA and some oxidized nitrite as well. Hyphal extracts of several of the nitrifying strains formed nitrite but not nitrate from 3-NPA; however, the extracts did not generate nitrate, nitrite, or 3-NPA from ammonium, hydroxylamine, β-alanine, aspartate, asparagine, malonylmonohydroxamate, 3-hydroxyaminopropionic acid, or N-hydroxyaspartate.

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