This study reports the cloning, expression, and characterization of recombinant cholesterol oxidase (ChOx) from Rhodococcus erythropolis in Escherichia coli BL21(DE3). The ChOx gene was inserted into the pET23b(+) vector using primers designed with site-specific modifications that enabled His-tag activation, expression, and purification by nickel-affinity chromatography to yield a protein of ∼55 kDa. A urea-gradient dialysis refolding protocol was employed to recover active enzyme from inclusion bodies. The purified enzyme exhibited a specific activity of 13.68 U/mg, representing a 2.5-fold improvement over previously reported recombinant ChOx yields with a recovery yield of 76.16 %. Cholesterol oxidation assays optimized enzyme concentration, substrate concentration, and temperature. Optimum activity occurred at 0.4 mg/mL enzyme and 20 mM cholesterol, achieving > 80 % substrate conversion, while the enzyme retained stability up to 50 °C. This work demonstrates a His-tag-assisted refolding strategy that efficiently produces active recombinant Rhodococcus erythropolis ChOx (RhoChOx). The optimization of catalytic parameters highlights the enzyme's robustness under diverse conditions. These findings establish RhoChOx as a promising biocatalyst for industrial cholesterol oxidation and provide a methodological framework applicable to other recombinant oxidases. © 2025 Elsevier Inc.