Partial Purification and Characterization of Cellulase (Ec.3.2.1.4) from Aspergillus niger Using Saw Dust as Carbon Source

Cellulase (EC.3.2.1.4) was isolated and partially purified from the submerged culture of Aspergillus niger through a simple four step purification step using homogenization to obtain crude filtrate, ammonium sulphate precipitation, carboxymethyl cellulose chromatography, and sephadex G-200 chromatography. A purification fold of 1.00 and 1.26 were gotten for crude filtrate and ammonium sulphate precipitation respectively, while 0.56 and 0.41 were gotten for carboxymethyl cellulose and sephadex G-200. The highest yield of 96.4% was recorded for (NH4)₂SO₄ precipitation. Kinetic studies gave Km and Vmax of 0.01 mg/ml and 1.02 μmole/ml/min for carboxymethyl cellulose and 0.02 mg/ml and 0.96 μmole/ml/min for sephadex G-200. Optimum temperature and pH of 40°C and 8.0 were obtained for the cellulase. Ethanol was found to inhibit the activity of the enzyme higher than other inhibitors tested. The implication of this is that given a more suitable carbon source and a longer culturing time, a very useful cellulase with commercial value could be produced.