| 摘要 |
PURPOSE:To produce a pullulanase having broad optimum pH range and excellent thermal stability, by culturing a pullulanase-producing microorganism belonging to Klebsiella genus in a medium containing a starchy polysaccharide added with lactose. CONSTITUTION:An enzyme-producing microorganism, such as a microbial strain belonging to Klebsiella genus and capable of producing pullulanase (e.g. Klebsiella pneumoniae) is cultured in a medium containing a nitrogen source and starch or amylopectin. The productivity of pullulanase can be increased remarkably by adding lactose to the medium. The optimum temperature of the pullulanase of the present invention is as high as 60-63 deg.C, and the pullulanase has excellent thermal stability. For example, there is little lowering of the activity of the enzyme by heating at 50 deg.C for 1hr in the absence of a substrate. Naturally, the enzyme has high thermal stability in the presence of a substrate or a metallic salt such as Ca salt, etc. Accordingly, the reaction can be carried out at 60 deg.C even under practical reaction conditions. |
