Diphtheria toxin muton CRM197 and its preparation process

The present invention is diphtheria toxin mutant CRM197 and its preparation process, and belongs to the field of immune protein carrier technology. The diphtheria toxin mutant CRM197 is expressed in colibacillus in the form of inclusion body, and the target product has sequence length of 536 amino acids, the immunogenicity the same as that of diphtheria toxin and no toxicity similar to that of diphtheria toxin. The present invention clones gene coding CRM197, constructs recombinant expression plasmid expressing CRM197 and transforms to colibacillus host for expression in the form of inclusion body. The present invention has target protein accounting for over 24 % of total protein content, high CRM197 purity over 95 % and high target protein recovering rate. The preparation process is simple, low in cost and suitable for industrial production.