Citric Acid Production by Aspergillus niger Using Molasses and Pumpkin as Substrates

3 Abstract: Two starchy substrates like pumpkin and cane molasses were selected for citric acid fermentation by using gamma ray induced mutant strains of 14/20 and 79/20 of A. niger under surface culture condition. Citric acid production was also different with various fermentation media by A. niger 14/20 and 79/20 strains. It was found to increase with the increase of fermentation period and maximum citric acid was found on day 13. In the presence of Prescott salt citric acid production was found lower than the absence of Prescott salt. Without Prescott salt highest values of citric acid production was found in mixed fermentation medium which were about 14.86 mg/ml and 14.44 mg/ml for A. niger 14/20 and 79/20 strains respectively, lowest production of citric acid was found in molasses medium for A. niger 14/20 and 79/20 strains were 7.72 and 7.57 mg/ml respectively. Whereas in the presence of Prescott salt, lowest production of citric acid in Pumpkin medium was found 2.86 mg/ml for A. niger 14/20 and 2.7 mg/ml for A. niger 79/20. Highest amount of citric acid was produced in molasses medium 4.88 mg/ml for A. niger 14/20 on day 13 with the presence of Prescott salt whereas 4.75 mg/ml for A. niger 79/20 strains respectively. Mixed substrate prepared with molasses and pumpkin media was proved to be the best and potential for citric acid production.