Phytase mutants

The invention relates to thermostable phytase, which comprises at least one pair of introduced disulfide bonds in the amino acid sequence of wild-type Escherichia coli phytase or mutant Escherichia coli phytase, and after introduction, the properties of the phytase can be improved, especially in the aspects of thermostable stability, steam-resistant stability and granulation stability. The phytase is obviously superior to the existing wild or mutant phytase; compared with the existing disulfide bond-introduced engineering modified phytase, the heat-resistant stability of the phytase is also remarkably improved. 本发明涉及热稳定性植酸酶，在野生型大肠杆菌植酸酶或突变型大肠杆菌植酸酶的氨基酸序列中包含至少一对引入的二硫键，引入后可以提升植酸酶的性质，特别是在于耐热稳定性，耐蒸汽稳定性，制粒稳定性方面，显著优于现有的野生型或者突变型植酸酶；相比于现有的引入二硫键的工程改造植酸酶，其耐热稳定性也有显著提高。