partial purification and characterization of b-galactosidase from aspergillus niger uv-5

the enzyme pgalactosidase from a mutant strain of a. niger uv-5 was partially purified using ammonium sulfate and acetone. the saturation range of 60-80% ammonium sulfate was found to yield 60.5% enzyme recovery with 2.4 fold purification. acetone precipitation at enzyme: acetone ratio of 1 : 1.5 brought about a higher yield i.e. 68% and three-fold purification. the combined procedures of 1.5 volume solvent fractionation followed by 50% ammonium sulfate precipitation brought about 8-fold purification with 40% enzyme yield. the optimum temperature of the enzyme was 65°c and the optimum ph was 4- 5. the pgalactosidase was strongly inhibited by galactose. comparative study of partially purified p-galactosidase in the present study with a commercial lactase from a. oryzae revealed comparable results