Abstract

A bacterial strain capable of producing high level of extracellular xylanase was isolated from soil. The characteristics of the isolated strain No.236 were identified to be Bacillus stearothermophilus. The maximal xylanase production was observed in the medium containing 0.75% xylan, 0.35% yeast extract, 1.06% $K_2$HPO$_4$and 0.05% CaCO$_3$with initial pH of 6.5 when the strain was cultured at 5$0^{\circ}C$ for 28 hrs with reciprocal shaking. Hydrolysis of xylan by the xylanase revealed that xylose was the only product of the reaction. This suggested that the enzyme produced by Bacillus stearothermophilus No. 236 was an exe-acting xylanase.

토양으로부터 세포외 xylanase를 다량 생산하는 균주를 분리하고 분리균의 형태적 내지는 생화학적인 특성을 조사하여 Bacillus stearothermophilus No.236로 동정하였다. 본 분리균은 초기 pH가 pH 6.5 인 0.75% xylan, 0.35% yeast extract, 1.06% $K_2$HPO$_4$, 0.61% NaH$_2$PO$_4$.2$H_2O$, 0.20% (NH$_4$)$_2$SO$_4$, 0.05% MnSO$_4$ 0.07% MgSO$_4$ 0.05% CaCO$_3$의 조성을 지닌 배지에서 5$0^{\circ}C$, 28시간 진탕배양했을 때 배양액 $m\ell$당 약 0.85units로서 가장 높은 효소생산량을 나타내었다. 또 본 xylanase는 xylan에 의해 유도 생산되는 세균 xylanase로서는 그 예가 극히 드문 exo-type의 효소인 것으로 판단되었다.

Keywords

• Identification;
• Bacillus stearothermophilus;
• exo-acting xylanase