Isolation and Enzyme Production of a Mannanase-producing Strain, Bacillus sp. WL-3.

A bacterium producing the extracellular mannanase was isolated from Korean formented food and has been identified as a member of the genus Bacillus from the result of the phylogenic analysis based on partial 165 rRNA sequences. The isolate, named Bacillus sp. WL-3, was shown to be similar to B. subtilis strain on the basis of its biochemical properties. The mannanase of culture supematant was the most active at $55^{\circ}C$ and pH 6.0. The additional carbohydrates including u-cellulose, avicel, oat spelt xylan, guar gum and locust bean gum (LBG) increased the mannanase productivity. Especially, the maximum mannanase productivity was reached 65.5 U/ml in LB medium supplemented with 0.5% (w/v) LBG, which was 131-folds more than that in LB medium. It was sug-gested that the increase of mannanase production was owing to induction of mannanase biosynthesis by LBG hydrolysates transported following initial hydrolysis by extracellular mannanase during the cell growth. The molec-ular weight of WL-3 mannanase was estimated to approximately 38.0 kDa by zymogram on SDS-PAGE.

Mannanase를 생산하는 Bacillus sp. WL-3 균주의 분리와 효소 생산성

전통 발효식품인 장류로부터 분리된 균으로 manna의 분해능이 우수한 Bacillus sp. WL-3는 형태적 특성, 생화학적 성질과 165 rRNA의 염기서열 등이 Bacillus subtilis와 유사성이 높은 것으로 확인되었다. 분리균이 생산하는 mannanase는 $55^{\circ}C$와 pH 6.0에서 최대활성을 보였으며 중성 pH에서 활성도가 높았다. 배지내에 $\alpha$-cellulose, avicel, oat spelt xylan, guar gum 및 locust bean gum(LBG)과 같은 고분자성 탄수화물을 첨가할 경우 mannanase생산성이 증가되었으며, 특히 LBC 0.5%함유한 LB배지에서 9시간 배양하였을 때 배양상등액내의 효소 활성이 65.5 U/ml로 최대 효소 생산성을 나타내 LBC 첨가하지 않은 배지에서 보다 효소 생산성이 131배 이상이 증가하였다. 균이 성장하는 동안 생성된 LBG가수분해 산물이 mannanas리 생합성을 유도하는 것으로 판단된다. 활성 염색을 통하여 Bacillus sp. WL-3의 mannanase를 분석한 결과 배양상등액에는 분자량이 약 38.0 kDa으로 추정되는 한 종류의 mannanase만이 존재하였다