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ABSTRACT
Extracellular β-galactosidase from Aspergillus orizae H 26–10–7 has been purified by procedures including ultrafiltration, precipitation with ethyl alcohol and ion-exchange chromatography on DEAE-cellulose as a result of which specific activity of 93 units/mg protein, purification of 18.2-fold and yield of 39.6% have been obtained. Some enzyme characteristics have been determined: molecular weight - 102 kD; Km - 1,61 mM for o-nitrophenyl-β-D-galactopyranoside and 69.36 mM for lactose; temperature and pH-optimum of activity - 60°C and pH 4.75 for both substrates. The enzyme preserves 80% of its activity at pH 5 and temperature of 55°C in the course of 6 hours. On the basis of these properties β-galactosidase from A. oryzae has been recommended for lactose hydrolysis in whey.