Effect of chemical and physical mutagens on amylase producing potentiality of Aspergillus flavus NSH9

Spergillus flavus NSH9 is a potential source of α-amylase and glucoamylases. Between two of its glucoamylases, one can digest the raw starch granules, while both being pH and thermostable. The purpose of the study was to enhance the production of amylases (α-amylase and Glucoamylase) from A. flavus NSH9 by random mutagenesis using Ultraviolet (UV) irradiation and Ethidium bromide (EtBr) treatment. Glucoamylase and α-amylase activity were evaluated by 3, 5-dinitrosalicyclic acid (DNS) method and starch-iodine method, respectively. Mutated A. flavus NSH9 by EtBr treatment (10µg/ml) in PDA plate produced highest amount of both crude glucoamylases (GA) (1.47 ± 0.087 U/mL/min) and raw starch degrading glucoamylase (RSD-GA) (0.839 ± 0.036 U/mL/Hour). The highest value was 1.6 and 1.5 times higher compared to control for GA and RSD-GA, respectively. Here as, UV induced radiation produced about 1.3 and 1.4 times more GA and RSD-GA compared to control, respectively. The activity of α-amylase was about 1.7 times higher in the treatment group with 5µg/ml EtBr in sublethal condition than without the treatment group. In conclusion, both UV and EtBr treatment increased the amylases production from A. flavus NSH9. As the single mutation process of A. flavus NSH9 enhanced all three enzymes, the strains could be used for the commercial production of amylase.