젖갈에서 분리한 유산균 Lactobacillus(L.) casei 2주와 L. pentosus 1주의 균체내 ${eta}-galactosidase$의 최적 생성조건과 특성을 조사하였다. ${eta}-galactosidase$의 최적 생성조건 조사에서, L. cosei No.10 균주는 탄소원으로 lactose를, L. Pentosus No.63 균주는 galactose를 1.0% 함유한 초기 pH 7.5의 MRS broth에서 $30^{circ}C$로 48시간 배양하였을 때로 확인되었다. L. casei No.36 균주는 lactose를 1.0% 함유한 초기 pH 6.5의 MRS 배지에서 $30^{circ}C$로 48시간 배양하였을 때가 최적 조건으로 확인되었다. 호소의 최적 활성 반응온도는 3 균주 모두 $60^{circ}C$였으며, L. casei No.10은 $45^{circ}C$까지, L. pentosus No.63은 $55^{circ}C$까지 90% 이상의 안정성을 나타내었다. L. casei No.36은 $40^{circ}C$까지 안정성을 유지하였으나 $55^{circ}C$에서 60%로 효소활성이 감소하였으며, 따라서 $40^{circ}C$까지 3균주 모두 90% 이상의 안정성을 나타내었다. 한편 효소활성의 최적 pH는 3 균주 모두 pH 6.5이었으며, L. casei No.10은 $pH;5.0{sim}6.0$, L. casei No.36은 $pH;5.0{sim}8.0$, 그리고 L. pentosus No.63은 $pH;6.0{sim}7.0$에서 각각 90% 이상의 안정성을 보였다.
Two strains of Lactobacillus(L.) casfi and one strain of L. Pentosus, which were isolated from pickles, were used to investigate in studing their characteristics of ${eta}-galactosidase$. The preferable carbon sources and pH of the MRS media for enzyme production from L. casei No.10 was found to be 1.0% lactose and pH 7.5, from L. Pentosus No.63 was 1.0% galactose and pH 7.5, and from L. casei No.36 was 1.0% lactose and pH 6.5, respectively. The maximum enzyme production from each strain was found after 48 hours culture at $30^{circ}C$ in a medium with preferable carbon source. The optimum reaction temperature with substrate for ${eta}-galactosidase$ activity was found at $60^{circ}C$ for all three strains . The stability of enzyme from L. casei No.36 was found to be at $45^{circ}C$, from L. Pentosus No.63 was found at $55^{circ}C$. This stability from L. casei No.36 was found at $40^{circ}C$, but it was reduced to 60% at $55^{circ}C$. These stabilities of enzymes remained about 90% at $40^{circ}C$ for all three strains. The optimal pH for enzyme activities was found to be pH 6.5 for all three strains. Enzyme activity remained over 90% for L. casei No.10 at $pH;5.0{sim}6.0$, for L. casei No.36 at $pH;5.0{sim}8.0$, and for L. pentosus No.63 at $pH;6.0{sim}7.0$.
