Background: Recombinant proteins overexpressed in E. coli are usually deposited in inclusion bodies. Cysteines in the protein contribute to this PROCESS. Inter- and intra-molecular disulfide bonds in chitinase, a cysteine-rich protein, cause aggregation when the recombinant protein is overexpressed inE. coli. Hence, aggregated proteins should be solubilized and allowed to refold to obtain native- or correctly- folded recombinant proteins.Methods: Dilution method that allows REFOLDING of recombinant proteins, especially at high protein concentrations, is to slowly add the soluble protein to REFOLDING buffer. For this purpose: first, the inclusion bodies containing insoluble proteins were purified; second, the aggregated proteins were solubilized; finally, the soluble proteins were refolded using glutathione redox system, guanidinium chloride, dithiothreitol, sucrose, and glycerol, simultaneously.Results: After protein solubilization and REFOLDING, SDS-PAGE showed a 32 kDa band that was recognized by an anti-chitin antibody on western blots.Conclusion: By this method, cysteine-rich proteins from E. coli inclusion bodies can be solubilized and correctly folded into active proteins.