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