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