Production and characterization of extracellular protease of mutant Aspergillus niger AB100 grown on fish scale

Fish scale, the chief waste material of fish processing industries was processed and tested for production of extracellular protease by mutant Aspergillus niger AB too. Protease production by A. niger AB(100) was greatly enhanced in presence of processed fish scale powder. Where as among the three complex nutrients tested, soya bean meal shows maximum stimulatory effect over protease production (2,776 mu mol/ml/min) when used in combination with glucose (5% w/v) and urea (2.5% w/v). The protease was optimally active at pH 7.0, retaining more than 60% of its activity in the pH range of 5-9. The enzyme was found to be most active at 50 degrees C and stable at 30 degrees C for I h. Purification of enzyme by CM-Cellulose and SDS-PAGE resulted in about 26-fold increase in the specific activity of the enzyme with a molecular weight of 30.9 kDa. HPLC study shows the purity of the enzyme as 75.92%. By the activating effect of divalent cations (Fe2+, Zn2+, Mn2+, Ca2+ and Mg2+) and inhibiting effect of chelating agent (EDTA) and Hg2+, the enzyme was found to be a metalloprotease.