An efficient enzymatic process for reducing yolk using Response Surface Methodology(RSM) was developed in this paper. In which COD concentration and dilution rate were found to be the most important factors influencing cholesterol conversion. Under the optimum operational conditions: incubation time of 14.15 h, water/solid ratio of 3.54 and COD concentration of 5.39 U/g, about 85.61% yolk cholesterol was reduced. After TLC analysis of the converted product, cholestenone was the only steroid like compound re...