Optimization of Citric Acid Production Using Aspergillus niger Isolated from the Leaf Litter Soil of Sathuragiri Hills

Soil samples were collected from the different locations in Sathuragiri Hills (Western Ghats, Tamilnadu). The Total Fungal Counts in the soil samples of the different locations were analyzed. The percentage frequencies of occurrence of fungal isolates are identified. The fungal isolates were identified based on the morphological and cultural characteristics they were identified as Cladosporium sp, Aspergillus niger, Penicillium sp, Alternaria sp, Curvularia sp, Helminthosporium sp and Aspergillus flavus. Among the isolates maximum amount of citric acid levels was produced by Aspergillus niger (2.2 ± 0.001 g/l). The effect of different pH, temperature, carbon source, nitrogen source, incubation time and agricultural residues on citric acid production by Aspergillus niger was analysed. The maximum amount of citric acid production was recorded in pH 6.0 (2.32 ± 0.09 g/l), temperature 30°C (2.85 ± 0.06 g/l), carbon source Glucose (6.08 ± 0.10 g/l). Nitrogen source ammonium chloride (10.22 ± 0.05g/l), incubation time 72 hours (13.56 ± 0.04 g/l) and agricultural residue corn ears (17.2 ± 0.14 g/l).