Mutants of Aspergillus niger N402, induced by UV mutagenesis, were selected and tested for resistance or sensitivity to 5-fluorocytosine. Some mutants showed increased citric acid production, which did not correlate with the intracellular amount of protein or ammonium ion. The resistance to 5-fluorocytosine proved to be a rational approach for isolation of new mutants with improved production of citric acid. The best mutant (FR13) accumulated double the amount of citric acid produced by the parental strain.
Aspergillus niger; citric acid; 5-fluorocytosine
