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.

Abstract: Provided is Lactobacillus kefiri MSR101, having the accession member being CGMCC No. 17506. The strain has acid resistance, bile salt resistance, resistance to phenol, antibiotic resistance, antioxidant activity, cell surface hydrophobicity, adhesion to intestinal epithelial cells, and a cholesterol-lowering function.

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.

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.

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.

Abstract: The present disclosure provides an Enterobacter chengduensis for producing NMN and application thereof, and relates to the technical field of screening and application of strains. The Enterobacter chengduensis of the present disclosure is determined as a Gram-negative bacterium and belongs to the genus Enterobacter chengduensis. When the Enterobacter chengduensis is used for producing the NMN by fermentation with the nicotinamide as a substrate, the yield of the NMN can reach 67.66 ?M, namely 22.6 mg/L, at 15 minutes, indicating that the wild strain has a strong activity to synthesize the NMN, the dependence on Nampt during synthesis of the NMN is reduced, and a high large-scale application prospect is achieved.

Abstract: Provided is Lactobacillus kefiri MSR101, having the accession member being CGMCC No. 17506. The strain has acid resistance, bile salt resistance, resistance to phenol, antibiotic resistance, antioxidant activity, cell surface hydrophobicity, adhesion to intestinal epithelial cells, and a cholesterol-lowering function.