RESUMO
In the course of mutation studies of Aspergillus niger strain AB with ethylene imine (1:4000), a mutant A. niger AB 501, produced greater amount of calcium gluconate in the culture broth (88.0 g/lit) as against the parent strain (36.0 g/lit) by the surface culture method of fermentation. This mutant was then exposed to UV-rays and a mutant, A.niger AB 1801, was found to produce high calcium gluconate in the culture broth (120 g/lit). The optimum cultural conditions for the production of calcium gluconate by A.niger AB 1801 were pH, 6.5; period of incubation, 9 days; volume of medium in 1 litre flask, 150 ml; temperature, 30 degrees C, volume of inoculum, 7.5 ml of cell suspension containing 2.6 x 10(7) spores and age of inoculum, 6 days old spores of A. niger AB 1801. The maximum yield of calcium gluconate to the above conditions was 168 g/lit. The cultural conditions that support maximum cultural growth did not, however, give optimal yield of calcium gluconate because after having yielded the maximum of calcium gluconate the growth of organism continued to increase further.