Isolation and Screening of Aspergillus niger Mutant for Improved Gluconic Acid Production

Gluconic acid (GA, C6H12O7, or 2, 3, 4, 5, 6-pentahydroxyhexanoic acid) is a mild organic acid resulting from the oxidation of D-glucose. Gluconic acid has low toxicity, low corrosion and form complexes with metal ions giving it wide application in several industries. This study aimed to isolate and screen for Aspergillus niger mutant for improved gluconic acid production. A total of 204 A. niger were isolated from different fruit and soil samples. Ninety-two (45%) out of the 204 isolates showed organic acid production potentials using bromocresol purple plate and gluconic acid production potentials using calcium carbonate agar plate. Ten out of the ninety-two (92) isolates were selected for strain improvement using UV mutation technique. After exposure to ultraviolet (UV) light of 254 nm at different time intervals of 2, 4, 6, 8, 10, 12 minutes respectively, A. niger AEAJP-2.110(PX939154) had the highest strain improvement for gluconic acid than A. niger AEAJP-2(PX954262), its wild type was exposed to a two- step UV light for 2 minutes with a yield increase from 54.1g/ml to 259.7g/ml (4.8-fold increase over the wild strain). In conclusion, this study established that UV light is a potent tool for enhancing gluconic acid production in A. niger.