Studies on Milk-clotting Enzyme of Dothiorella ribis -Part II. Properties of the Enzyme-

Dothiorella ribis가 생산하는 응유효소에 관한 연구 -제 2 보 응유효소로서의 일반적 성질-

The amount of the milk clotting enzyme which is produced by Dothiorella ribis in wheat bran was 950 Soxhlet units per gram of wheat bran. The milk clotting activity of this enzyme was increased by the elevation of clotting temperature and by the increase of the addition of $CaCl_2$ to milk. It was also increased when the pH of milk was lower than that of the fresh milk. When milk was diluted by distilled water, the milk clotting activity of the enzyme was decreased. And its milk clotting activity was good when milk was pasteurized at low temperature. The enzyme of Dothiorella ribis has larger proteolytic activity per Soxhlet unit than that of the milk clotting enzyme of Mucor pusillus Lindt. This enzyme was rather stable between pH 6 and pH 8 when it was conditioned for ten minutes. The heat stability of enzyme was tested by treating it under the condition for $10{\sim}60$ minutes. And the enzyme was stable under the temperature of $45^{\circ}C$. Also the recovery of protein as a form of curd was 76.2 percent to the total protein content of milk.

Dothiorella ribis에 의한 응유효소의 생산량은 밀기울 1g 당 950 S.U.이며 응유온도는 $20{\sim}62^{\circ}C$의 온도범위에서 온도상승과 더불어 응유력이 강화되었고 calcium의 농도는 짙어 질수록 탈지분유액의 pH는 보다 산성일 때 응유력이 강화되었다. 우유가 희석될 때 0.01M $CaCl_2$용액을 사용한 경우는 생우유나 탈지분유에 관계없이 희석과 더불어 응유력이 증가되었으나 증류수로 희석할 때는 희석도가 낮을 때 다소 응유력의 증가를 보이다가 희석도가 높아지면 급격히 응유력이 감퇴 됨을 알수 있었다. 또한 우유는 저온처리하는 것이 응유활성의 측면에서도 유리하다는 것을 나타내 주었으며 단백질분해력은 같은 응유력에 대하여 비교검토된 Mucor pusillus Lindt의 응유효소에 비하여 월등히 높았다. pH의 안정범위는 중성부분이며 열에 대하여는 $45^{\circ}C$에서 비교적 안정하였고 우유를 응고시킨 후 curd로서의 단백질 회수율은 76.2%이었다. 이상의 결과로서 Dothiorella ribis의 응유효소는 단백질분해력이 높다는 결함이 있으나 보다 연구할 가치가 있으며 단백질분해효소로서의 개발도 또한 기대된다.