Production,Purification and Properties of Ribonuclease from Aspergillus niger

Aspergillus niger NRC–A–1–233 was cultivated by the shaking method. The optimal cultural conditions for ribonuclease (RNase) production were: composition of medium: sucrose, 15%; NH₄NO₃, 0.2%; KH₂PO₄, 0.1%; MgSO₄·7 aq., 0.025%; initial pH, 2.2; shaking conditions: 50 ml of medium /500 ml flask; cultivation time, 120 hr. The RNase was purified by acid clay treatment and chromatography on DEAE-cellulose and Sephadex G–75 columns. The purified RNase was homogeneous by ultracentrifuge and disc electrophoresis.

The molecular weight of the RNase was estimated to be 28,500 on SDS-polyacrylamide gel and its isoelectric point was 2.8 by Ampholine electrofocusing method. Digestion rate of RNA by the RNase was 100%. The RNase did not have an exact base specificity and produced four kinds of 3′-nucleotides from yeast RNA.