Purification and characterization of an acid protease produced by a mutant strain of Aspergillus niger

Aspergillus niger, isolated from the soil, secretes an acidic protease into the medium on exposure to UV-irradiation for 1, 2; 3, h, the organism was Mutated and the mutants thus obtained were screened for maximum protease production. This extracellular protease was purified to apparent homogeneity by chromatography on DEAE-cellulose. Homogeneity was ascribed by electrophoresis. The molecular weight, as determined by SDS-PAGE was 39800 daltons. This protease has an optimum activity at a pH of 6.0 and temperature of 37 C. It is inhibited by metal ions like Cu2+ but is active in the presence of metal ions like Mn2+ and Mg2+.