普鲁兰酶广泛应用于食品领域，尤其是特异性较高的I型普鲁兰酶。随着基因工程技术的发展，人们通过基因工程手段，在一定程度上有效提高了普鲁兰酶的产量及稳定性（酸碱稳定性及热稳定性），但所产的普鲁兰酶其他酶学特性仍有缺陷，依然不能完全满足工业需求。随着研究的深入，人们发现通过半理性设计改善酶稳定性的同时，一些酶的催化效率及底物特异性有一定的提升，但其机理尚未明确。本研究以巨大芽孢杆菌I型重组普鲁兰酶为研究对象，通过理性设计及半理性设计（本研究主要通过迭代饱和突变法、结构域截短、结构域切换），提升该重组酶催化效率，比活力以及合成能力特性，研究其构效关系，为得到更适宜工业化应用的普鲁兰酶提供理论支持。

Pullulanase is widely used in the field of food, especially the type I. With the development of genetic engineering technology, People have obtained some kinds of recombinant pullulanase by genetically engineered method. which increased production effectively and stability (pH stability and thermostability) to a certain extent. However, there is few enzyme characteration can fully meet the industrial needs. It was found that catalytic efficiency and substrate specificity were improved in several recombinant pullulanases as increasing enzyme stability by semi-rational design. However, the mechanism is not clear. In this study, improving of catalytic efficiency, specific activity and synthetic ability of the type I pullulanase from Bacillus megaterium and structure-activity relationship will be studied by rational design and semi-rational design (this study mainly through iterative saturation mutation method, domain truncation, domain switching), which could provide theoretical support to get more suitable pullulanase for industrial application.