Mutant breeding of Aspergillus niger irradiated by t2C6＋ for hyper citric acid

In this study, strains of Aspergillus niger 4# for hyper citric acid were irradiated to different doses by 80 MeV/u 12C6＋ ion beams. Seven mutant strains showed marked citric acid over-production records and faster productivity than initial Aspergillus niger 4# by shaking flash fermentation. The maximum product yield was 132.8 g L-I（ the H4002 strain） being a 8.8% increase to the initial strain. The scale-up experiment was carried out in a 100 L bioreactor. The mutant H4002 can accumulate 187 g L 1 product yield of citric acid from starch liquefying supernatant. The productivity of citric acid was 2.75 g L-1 h-1. So, the mutant H4002 possesses rapid sugar katabolism for producing citric acid. Meanwhile, the pellet morphology kept compact and round during the whole submerged fermentation, which was suited to produce citric acid. The results indicate that mutant H4002 has potential ability to produce citric acid rapidly.