Citric acid fermentation by mutant strain of Aspergillus niger GCMC-7using molasses based medium
Citric acid fermentation of cane-molasses by submerged fermentation in 15 L stirred fermentor (working volume 9 L) was carried out. A hyper mutant strain of Aspergillus niger GCMC-7 was used in the present study which was obtained from the culture collection of our own labs. Ferrocyanide treated molasses [K4Fe(CN)6 200 ppm] medium containing sugar 150 g/l was employed as the basal fermentation medium. Different cultural conditions such as incubation temperature (30ºC), initial pH (6.0), air supply (1.0 l-1l-1min), agitation intensity (200 rpm) and time profile (144 h after inoculation) were optimised for enhanced citric acid production. Maximum amount of anhydrous citric acid obtained during the course of study was 106.65 g/l, with a sugar consumption of 107 g/l. Final pH, ferrocyanide concentration and dry cell mass were 2.1, 60 ppm and 16.5 g/l, respectively.