Abstract:
Aspergillus Niger 0-2-1 was used as original strain.This strain of separation and purification of spores protoplast was treated by Ultra Violet ( UV) . The mutant with the bigger ratio of hydrolyzation circle diameter to bacterial colony diameter was screened so as to assay acid α- amylase activities. After genetic stability testing, three strains ( UV9, UV17, UV31) with an high activity of acidα-amylase were screened.Strain UV9, UV17 and UV31 were obtained with an acid α- amylase activity of 184.66, 162.73 and 167.31U /mL.The activities obtained were 54.9%, 38.1% and 42.0% higher than that of the parent strain.