Cholesterol oxidase, CO enzyme is a monomeric oxidoreductase flavoenzyme, catalyzing oxidation of cholesterol to cholesterone and hydrogen peroxide. CO is an industrially important enzyme used in the clinical determination of serum cholesterol levels. Furthermore, CO is used in the biological processes involving conversion of different steroidal and nonsteroidal compounds. Moreover, CO has been used as an insecticide in transgenic crop-pest management. CO enzyme biosensors have found applications in the detection of cholesterol level in various samples and have also scientific importance in investigating cell membrane interactions with cholesterol. Due to its vast range of applications, the industrial importance and demand of CO have gained increased interest. Current work describes the isolation of a potential cholesterol oxidase producing streptomycete from Egyptian soil. The isolated strain produced cholesterol oxidase in submerged culture using a medium containing glucose, yeast extract, malt extract, and CaCO3 with the addition of cholesterol as an inducer. The isolated strain was identified as Streptomyces rochei NAM-19 based on 16S rRNA sequencing and phylogeny. Optimization of cholesterol oxidase production has been carried out using response surface methodology. The Plackett-Burman design method was used to evaluate the significant components of the production medium followed by Box-Behnken experimental design to locate the true optimal concentrations, which are significantly affecting enzyme production. Results showed that the predicted enzyme response could be closely correlated with the experimentally obtained production. Furthermore, the applied optimization strategy increased volumetric enzyme production by 2.55 times (65.1 U/mL) the initial production obtained before medium optimization (25.5 U/mL).
