Isolation and mutation of local strains of A. niger for citric acid production

Abstract EN

- Tow strains.

One from Irbid soil and the other from Al-Mafraq soil.

Were isolated and produced 10 and 13 g/L citric acid respectively under submerged condition using sucrose medium.

The identification of the two strains was confirmed by the International Mycological Institute as A.

Niger Van Tieghum and were given the international numbers IMI 376168 and IMI 176769.

Under solid-state fermentation condition.

The Irbid strain gave higher citric acid production (34g/kg) than the Mafraq isolate (22 g/kg) and than the imported strain IMI 309921 (27 g/kg) under solid-state fermentation conditions using carob as a solid medium.

The Irbid strain was exposed to twelve rounds of exposure by u.v and gamma rays and alternations of the two.

A mutant G4 was selected from gamma ray line and produced 60g/kg citric acid under solid-state fermentation conditions using carob as a solid medium.

Higher production of citric acid (54g/kg) was obtained from this strain when grown on carob as a solid substrate.

much less production was a chieved (18 g/kg) with olive pomace.

The optimum moisture content of the solid substrate (carob) for citric acid production was 71%.

At which the wild type and the mutant G4 produced the highest amount of citric acid (38 and 62 g/kg respectively).