Effect of Gamma-Ray Induced Mutant Strains of Aspergillus niger on Citric Acid Fermentation Using Molasses and Jackfruit Based Medium

4 Abstract: Aspergillus niger is most commonly known among the various fungal strains screened for citric acid production, when cultivated in carbohydrate-rich medium of fermentation. In the present study, a number of indigenous raw materials such as molasses and jackfruits have been used for citric acid production. The previously isolated gamma-ray induced second step mutants 14/20 and 79/20 of A. niger were reradiated by Co 60 Gamma beam-650 source at a dose rate of 0.674 kGy/hr aiming to further increase the production of citric acid. In absence of Prescott salt and in mixed fermentation medium the highest production of citric acid was found by further mutated. A. niger 14/20 with gamma radiation at 20 Krad which was about 16.16 mg/ml and lowest citric acid production was found in molasses media by further mutated A. niger 14/20 with gamma radiation at 10Krad which was found 9.22 mg/ml on the day 13 but it was higher than that produced by the un irradiated strain. In absence of Prescott salt highest production of citric acid was found by further mutated A. niger 79/20 with gamma radiation at 20 Krad in mixed fermentation medium which was about 15.94 mg/ml. Lowest citric acid production was found in molasses media by further mutated A. niger 79/20 with gamma radiation at 10 Krad which was found 9.08 mg/ml on the day 13 but it was higher than that produced by the un irradiated strains.