Citric acid production with mixed strains of Aspergillus niger in submerged culture.

Citric acid yield of 8 different strains of Aspergillus niger in pure and mixed cultures was investigated. The yield varied remarkably with the strain and combination of strains. Generally, the yield of citric acid for a given strain was higher in pure than in mixed culture. However, low yielding strains in combination often augmented the yield under mixed culture. The possibility of an additive genic effect is discussed.