Production of Endo-Polygalacturonase of a Mutant of Aspergillus niger

Aspergillus niger의 변이주(變異株)에 의(依)한 Endo-polygalacturonase의 생산(生産)

Aspergillus niger B-15 with strong Endo-polygalacturonase (Endo-PG) activities was selected out from a total of 1,573 fungal strains isolated from various testing materials. A mutant strain, U-46, was obtained from the Aspergillus niger B-15 by repeated irradition of ultra-violet light. The objectives of the study were to investigate the fungal properties of the parental and mutant strains obtained and to study the condition of enzyme production and reaction. The results obtained are summarized as follows: 1. The size of conidial head of the U-46 mutant was smaller than that of the parental strains, B-15 and the length of the conidiophore was also shorter than that of the parental strains. 2. The optimum conditions for the Endo-PG production of the parental B-15 strain in the wheat bran Koji were obtained when 40% of water was added to the wheat bran and the temperature was 30 to $35^{\circ}C$. However, the best condition for the mutant U-46 strain was attained when 60 to 70% of water was added and the temperature was $35^{\circ}C$. The optimum growing periods were two to three days for both parental and mutant strains. 3. Under the optimum producing conditions of each strains, the enzymatic activity of the mutant U-46 was 20 times higher than the Endo-PG of the parental strain, B-15. 4. When both strains were cultured in the wheat bran Koji containing 60% of water at $35^{\circ}C$ for three days, the mutant strain. U-46, was about 46 times higher in the Endo-PG activity and about 18 times greater in Exo-PG activity than the parental strain, B-15. The activities of cellulase, $\alpha$-amylase, and glucoamylase were also highly increased in the mutant strain. 5. The mutant strain, U-46, increased its Endo-PG activity up to 20% over that of ordinary case when 1.2 to 1.5% of ammonium sulphate was added to the wheat bran. 6. The optimum condition for Endo-PG activity of crude enzyme of the mutant strain, U-46, was attained when pH of reaction solution was 4.0 to 4.5 and the temperature was $50^{\circ}C$.

각종(各種) 시료(試料)로부터 1,573주(株)의 균주(菌株)를 분리(分離)하고 그 중에서 endo-polygalacturonase (Endo-PG) 활성이 강한 Aspergillus niger B-15를 선발하였다. 이어서 선정균주(選定菌株)에 자외선을 연차적(連次的)으로 조사(照射)하여 변이주(變異株) U-46을 얻었으며 친주(親株)와 변이주(變異株)의 균학적성질(菌學的性質)을 조사(調査)하고 변이주(變異株)의 효소생산조건(酵素生産條件)과 반응조건(反應條件)을 검토(檢討)하여 아래와 같은 결과를 얻었다. 1. 변이주(變異株) U-46은 친주(親株)보다 분생자두(分生子頭)의 크기가 작아지고 분생자병(分生子柄)의 길이가 짧아졌다. 2. 밀기울배지에서의 배양(培養)에 있어서 Endo-PG생산(生産)을 위한 최적조건(最適條件)은 친주(親株) B-15의 경우 밀기울에 대한 첨수량(添水量) 40%, 배양온도(培養溫度) $30{\sim}35^{\circ}C$였으나 변이주(變異株) U-46의 경우는 밀기울에 대한 첨수량(添水量) 60~70%, 배양온도(培養溫度) $35^{\circ}C$였다. 배양일수는 어느 것이나 2~3일간이 적당하였다. 3. 친주(親株)와 변이주(變異株)를 각각의 최적조건(最適條件)에서 배양(培養)할 경우 친주(親株) B-15의 Endo-PG에 비하여 변이주 U-46의 효소활성은 약 20배 높았다. 4. 밀기울배지(밀기울에 대한 첨수량(添水量) 60%)에 $35^{\circ}C$, 3일간 배양할 경우 변이주 U-46 은 친주(親株)에 비하여 Endo-PG 활성이 약 47배(倍)로, Exo-PG 활성은 약 18배로 증가되었으며 cellulase, ${\alpha}$-amylase 및 glucoamylase 활성도 증가되었다. 5. 밀기울에 $(NH_4)_2SO_4$을 1.2~1.5% 첨가(添加)한 배지에서 변이주(變異株) U-46의 Endo-PG 활성(活性)은 약 20% 증가되었다. 6. 변이주(變異株) U-46의 조효소액(粗酵素液)의 Endo-PG 반응(反應) 최적조건은 pH 4.0~4.5, $50^{\circ}C$이었다.