The isolation and mutagenic improvement of Aspergillus niger for production of Citric Acid

Aspergillus niger is used in the production of citric acid. The aim of this study was to isolate A. niger and to subject random mutagenesis by UV radiations, ethidium bromide and sodium azide for producing mutant A. niger strain capable of overproducing citric acid. A. niger strains were isolated from seventy-five mud samples. They were subjected to random mutagenesis by UV radiations, ethidium bromide and sodium azide to improve the citric acid production capacity. Their citric acid production capacity was tested in shake flask and fermenter studies. Mutant and wild strain were compared for their citric acid production ability, glucose utilization and yield. Some mutants produced more citric acid with higher consumption of glucose compared to parental strains. The mean glucose consumption and citric acid production among five A. niger strains during fermentation period are significantly different (P<0.05). Of all mutant generated by UV exposure for 70 min produced higher concentration of citric acid. This study proved that citric acid production was increased with UV and chemicals mutated A. niger strains compared with wild strains. This mutational work has a potent A. niger strain for production of citric acid.