Fish scale, the chief waste material of fish processing industries was processed and tested for production of extracellular protease by mutant Aspergillus niger AB 100 . 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 lmol/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°C and stable at 30°C for 1 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 (Fe 2+ , Zn 2+ , Mn 2+ , Ca 2+ and Mg 2+ ) and inhibiting effect of chelating agent (EDTA) and Hg 2+ , the enzyme was found to be a metalloprotease.

No abstract

The mineral requirements of a strain of Aspergillus niger for the production of citric acid in a synthetic medium were studied. It was observed that K2HPO4 and MgSO4. 7 H2O were required at concentrations of 0.1% and 0.02% respectively. The optimum level of each of the trace elements Fe, Mn and Zn was 1.0 mug/ml. NaC1 and CaC12 at lower concentrations had no effect on citric acid production. Trace elements, Cu, Co and Mo, had an adverse effect on the production of citric acid while Ni and V were without effect.

No abstract

No abstract