Basal Screening Fermentation Medium: The isolate Aspergillus spp were screened quantitatively for
the production of citric acid in liquid culture medium containing soluble starch – 10 gm/L; (NH 4 ) 2 SO 4 – 2.2
gm/L; K 2 HPO 4 – 1 gm/L; MgSO 4 .7H 2 O – 0.05 gm/L; CaCl 2 – 0.05 gm/L. The basal screening media was
autoclaved at 121°C for 15 minutes. The basal medium was inoculated with 1ml of the spore suspension of the
concentration 2 x 10
8
spores/ml prepared from 5 days old cultures of the isolated Aspergillus strains. A total of 8
Aspergillus strains were screened for citric acid production. Based on the screening results for citric acid yield,
only Aspergillus niger S-6 was selected for further study.