Citric Acid Production by Aspergillus niger Cultivated on Parkia biglobosa Fruit Pulp

The study was conducted to investigate the potential of Parkia biglobosa fruit pulp as substrate for citric acid production by Aspergillus niger. Reducing sugar was estimated by 3,5-dinitrosalicylic acid and citric acid was estimated spectrophotometrically using pyridine-acetic anhydride methods. The studies revealed that production parameters (pH, inoculum size, substrate concentration, incubation temperature, and fermentation period) had profound effect on the amount of citric acid produced. The maximum yield was obtained at the pH of 2 with citric acid of 1.15 g/L and reducing sugar content of 0.541 mMol(−1), 3% vegetative inoculum size with citric acid yield of 0.53 g/L and reducing sugar content of 8.87 mMol(−1), 2% of the substrate concentration with citric acid yield of 0.83 g/L and reducing sugar content of 9.36 mMol(−1), incubation temperature of 55°C with citric acid yield of 0.62 g/L and reducing sugar content of 8.37 mMol(−1), and fermentation period of 5 days with citric acid yield of 0.61 g/L and reducing sugar content of 3.70 mMol(−1). The results of this study are encouraging and suggest that Parkia biglobosa pulp can be harnessed at low concentration for large scale citric acid production.