CRM197, a genetically detoxified diphtheria toxin, is widely used as a carrier protein in conjugate vaccines, including effective conjugate vaccines against Streptococcus pneumoniae, Haemophilus influenzae b and Neisseria meningitidis. Fina BioSolutions has developed a highly efficient E. coli expression system for CRM197. We express soluble, properly folded CRM197 in the cytoplasm of E.coli. High expression levels and a simple purification scheme allow us to produce CRM197 at low cost and price it accordingly.