Investigation of increased production of citric acid by Aspergillus niger mutant native strains

Aspergillus niger were isolated from the soil and surface of corn seeds purified and identified according to morphological characteristics. The irradiation rate was calculated based on the duration of UV radiation received in Jules per square meter. The specific method of Marier and Boulet was used to quantitatively measure the production of citric acid. Radiation with 1200 seconds showed the greatest effect on the increase in the production of citric acid. The mean production of citric acid in the preferable mutated isolates and parents were 51.01 and 37.87 mg/l respectively, which increased by 14.14 g/l. In the study of the stability of mutated genotypes, the mean production of citric acid in 1200 seconds of radiation in the fourth consecutive culture of the first culture was not statistically significant. The performance and efficacy of mutated isolates (5uv) showed an increase in the production of citric acid by about 3 times compared to parent isolates. In isolation of 5uv and its parents, the kinetic parameters of product formation (citric acid) were twice as high and the kinetic parameters of the substrate (glucose consumption) were approximately equal, while the dry weight of the cell mass in the isolate 5uv increased relative to the parental isolate 5 with the same gradient. In this study, it was found that random mutations with UV radiation have improved the kinetic parameters of the production of citric acid versus glucose consumption as a substrate.