Abstract: The present invention discloses a microcapsule powder stable in gastric acid, a method for preparing the same and use thereof. The microcapsule powder comprises a core material and a capsule material coated outside the core material, wherein the capsule material has a melting point of greater than 42° C., and the capsule material does not decompose or dissolve under the action of protease and gastric acid, but decomposes under the action of intestinal digestive enzymes. The core material is coated with the capsule material in the microcapsule powder, thus achieving high-efficiency coating of the core material by a single component. The microcapsule powder achieves conventional intragastric stability as well as favorable stability in an open environment at room temperature, thus solving the problem that the conventional embedding solution may only achieve intragastric stability, but the stability in an open environment at room temperature is low.

Abstract: The present disclosure provides an innovative method for improving the enzyme activity of an NMN biosynthetic enzyme Nampt, and relates to the technical field of genetic engineering. A mutant protein of the present disclosure is obtained by firstly analyzing a target protein Nampt using two softwares FoldX and DeepDDG, and then predicting multiple key sites influencing the enzyme functions and finally performing the semi-rational design of the enzyme. In the examples of the present disclosure, 10 mutant strains are constructed using the designed primers according to the principle of point mutation, and 8 of the mutants have higher activity than a wild-type strain, in which the NMN yield of the mutant Nampt-V365L is increased by 62%, and the NMN yields of the mutants Nampt-S248A, Nampt-N164L, Nampt-S382M, Nampt-A245T and Nampt-A208G are increased by 34%, 27%, 27%, 22% and 17% respectively.