토양에서 분리한 여러가지 곰팡이류 가운데 beta-galactosidase 생성력이 가장 좋은 Aspergillus niger CAD 1을 효소 생산 균주로 선정 하였다. 이 균주의 효소 생산 최적 배양조건은 밀기울에 0.5% 탈지 분유를 첨가한 배지를 $30{circ}C$에서 72시간 정치배양하는 것이었다. 아세톤으로 침전시킨 조효소(crude enzyme)는 일차로 DEAE-cellulose, 2차로 Sephadex G-100 gel filtration에 의하여 1,387배로 정제되었고 이때의 수율은 6.2%이였다. 정제된 효소의 최적 온도는 $45{circ}C$ 최적 pH는 4.5이었으며, 기질로서 ONPG와 유당에 대한 Km값은 각각 $3.57{ imes}10^3M$과 $83.3{ imes}10^3M$, Vmax값은 각각 33.0 unit/mg protein과 15.38unit/mg protein이었다. 활성화 에너지는 9,900cal/mol이었으며 효소활성 및 안정제로 금속이온을 필요로 하지 않았다. 50ml의 탈지유, 4.8%유당 용액, 유청용액에 효소 5ml(182 unit/ml)를 침가하여 $45^{circ}C$에서 10시간 반응시켰을 때의 유당 분해율은 각각 65%, 70%, 78%를 나타내었다.
A strain of Aspergillus niger CAD 1 which produces considerable amount of beta-galactosidase was selected from extracellular beta-galctaosidase producing fungi isolated from soil. Optimal conditions for the enzyme from Aspergillus niger CAD 1 were the growth in wheat bran supplemented with 0.5% skim milk powder at $30^{circ}C$ for 72 hrs. The crude enzyme was purified 1,387 fold through DEAE-cellulosc and Sephadex G-100 chromatographr and its recovery was 6.2%, The optimal pH and temperature for the purified enzyme were pH 4.5 ana $45^{circ}C$, respectively. The Km and Vmax on ONPG were $3.57{ imes}10^3M$ and 33.0 unit/mg protein, whereas those on lacose were $83.3{ imes}10^3M$and 15.33 unit/mg protein, respectively, The activation energy for the enzyme was 9,900 cal/mol and the enzyme had no metal ion requirement for its activity and stability. The hydrolysis of lactose in skim milk, 4.8% lactose solution and acidic whey were 65%, 70% and 78% after 10 hrs incubation at $45^{circ}C$, when 182 units of the enzyme were used 50ml of the substrate solutions.
