A comparative study of the ability of the fungus Aspergillus niger on two alternative media, wheat bran and rice husk.

Citric acid is one of the important organic acids in the fields of industry, agriculture, medicine, etc., and it can be obtained in many ways, the best of which is biological methods using microorganisms. The current study aimed to prepare two cheap and environmentally friendly culture media for the purpose of producing citric acid from Aspergillus niger. The two media, one from rice husks and the other from Wheat bran, where a comparison was made between them regarding which is more efficient in supporting the fungus A. niger compared to the standard medium, the best temperature and pH for production were also assessed. Eight isolates were obtained, all of which produced acid to varying degrees. No.1 was the highest and best in terms of production 3.1 gm/l, followed by isolate No. 2 with an amount of 2.5 g/l. It was observed that the amount of acid produced increased with the increase of the biomass of the fungus. The study showed variable results regarding the production of citric acid from isolates of A. niger, where the wheat bran medium was the best result, where the resulting concentration of acid was 5.1 gm/l, compared to 4.4 g/l for the medium of rice husks. The results showed that the best temperature was 25°C, as it gave a concentration of citric acid of 3.4 g/l, while the best pH was 6 where the concentration of citric acid produced It was 3 grams per liter.the study showed that there were no significant differences with regard to the sugars adopted in this experiment, as it gave significant similar results in terms of the amount of acid produced as well as the biomass of the fungus Aspergillus niger, while ammonium nitrate was the best among the nitrate sources used, with a production quantity of 4 gm/l .