The recombinant human interferon-γ (rhIFN-γ) was overexpressed as inclusion bodies in Escherichia coli. After ultrasonic homogenization and centrifugation

inclusion bodies of rhIFN-γ were obtained. The inclusion bodies were then purified by coupling wash steps in Triton X-100 and finally were dissolved in 8 mol8226;L-1 urea. A refolding process by hydrophobic interaction chromatography (HIC) was proposed. Refolding methods with no urea gradient and linearly decreasing urea gradient were performed.The effects of final urea concentration

urea gradient length

flow rate and protein loading on the refolding were investigated in detail. Under the optimum condition in the refolding with linearly decreasing urea gradient

the activity yield of rhIFN-γ was 6.5 times of that in the dilution refolding process and the protein mass yield was up to 36% with specific activity 1.9×108 IU8226;mg-1.