Abstract

In the acidic LB plate, a bacterial strain was isolated from homemade soybean paste as a producer of the extracellular mannanase. The isolate YB-1402, which was a Gram-positive rod-shaped bacterium with spore, has been identified as Bacillus amyloliquefaciens on the basis of its 16S rDNA sequence and biochemical properties. Maximum mannanase productivity of the isolate YB-1402 was reached approximately 150 U/ml in LB broth supplemented with konjac (3.0%). The molecular mass of YB-1402 mannanase was estimated to approximately 38.0 kDa by zymogram of the culture filtrate on SDS-PAGE. The mannanase of culture filtrate was the most active at $55^{\circ}C$ and pH 5.5. The mannanase activity was completely maintained after pre-incubation at pH 3.0 to 10.0 for 1 h. The predominant products resulting from the mannanase hydrolysis were mannose, mannobiose and mannotriose for LBG or mannooligosaccharides. The enzyme could hydrolyze mannooligosaccharides larger than mannobiose.

된장으로부터 mannanase 생산균으로 산성 배지에서 분리된 YB-1402는 그람양성 간균으로 포자를 형성하며, 16S rDNA 염기서열과 생화학적 성질이 Bacillus amyloliquefaciens와 가장 높은 유사도를 보였다. 분리균 YB-1402는 konjac을 3% 첨가한 LB 액체배지에서 약 150 U/ml의 최대 mannanase 생산성을 보였다. 분리균의 배양상등액을 사용하여 SDS-PAGE 활성염색을 실시한 결과 분자량이 약 38 kDa로 추정되는 한 종류의 mannanase만이 관찰되었으며, $55^{\circ}C$와 pH 5.5 반응조건에서 mannanase의 최대활성을 보였다. 특히 mannanase는 pH 3.0-10의 범위에서 1시간 방치하였을 때 실활되지 않은 특성을 지니고 있었다. Locust bean gum과 mannooligosaccharides를 mannanase로 분해하였을 때 mannose, mannobiose와 mannotriose가 최종 분해산물로 관찰되었으며 mannotriose 이상의 중합도를 갖는 mannooligosaccharides를 분해하는 것으로 확인되었다.

Keywords

• Bacillus amyloliquefaciens;
• mannanase;
• productivity;
• property