Characteristics of ${\beta}-Galactosidase$ Produced from Lactobacillus acidophilus

Lactobacillus acidophilus가 생성하는 ${\beta}-Galactosidase$의 성질

The characteristics of endogenous and exogenous ${\beta}-galactosidase\;({\beta}-Galase)$ produced from L. acidophilus were investigated as one of the serial studies on the fermentation of Chinese cabbage kimchi using L. acidophilus. Apparent molecular weight of endogenous and exogenous of the ${\beta}-Galase$ were investigated to be 550,000 and 740,000 daltons by the method of gel filtration and Km values of the both enzymes were 1.67mg/ml, 1.33mg/ml and $V_{max}$ were $8.5\;{\mu}\;mol/mg/30min.$, $2.65\;{\mu}\;mol/ml/30min.$, respectively. The optimum pH of the enzymes were 7 and 8, respectively. The optimum temperatures and salt concentrations of the both enzyme were the same and appeared to $30^{\circ}C$and$4{\sim}5%$, respectively. The activities of the endogenous and exogenous ${\beta}-Galase$ were decreased by increasing of temperature from $60^{\circ}C$to$90^{\circ}C$ and the decreasing rate of the enzyme activities on the processing of the heating times showed high at first 2 minutes of heating.

Lactobacillus acidophilus를 이용한 배추김치 제조 연구의 일환으로 이 균이 생성하는, 김치의 연화와 밀접한 관련이 있는 효소의 하나인 ${\beta}-galactosidase\;({\beta}-Galase)$의 성질을 균체내외 효소로 구분하여 조사하였다. Gel여과법에 의하여 측정한 균체내외 ${\beta}-Galase$의 개략적인 분자량은 각각 550,000 및 740,000 dalton이었으며 $K_{m}$값은 각각 1.67mg/ml 및 1.33mg/ml $V_{max}$은 각각 $8.5{\mu}mol/mg/30min$ 및 $2.65{\mu}\;mol/ml/30min$이었다. 최적 pH는 균체내 효소의 경우는 7, 균체외 효소는 8이었으며 최적온도는 다같이 $30^{\circ}C$ 최적 소금농도는 $4{\sim}5%$이었다. ${\beta}-Galase$의 열에 대한 안정성은 $60^{\circ}C$에서 $90^{\circ}C$로 온도가 높아질수록 그리고 열처리 시간이 길어질수록 감소하였는데 최초 열처리 2분간의 감소율이 가장 높았다.