Maximization of cholesterol oxidase production by Rhodococcus equi no. 23 By using response surface methodology

Medium optimization for the production of cholesterol oxidase (EC 1. 1.3.6) by Rhodococcus equi no. 23 was investigated by using response surface methodology and a central composite design. Results revealed that cholesterol and yeast extract had positive effects and the interaction between any two of three factors had no significant effect on cholesterol oxidase production. The optimized medium was the basal medium with the addition of 2.30 g/l cholesterol, 8.18 g/l yeast extract and 4.10 ml/l Tween 80. The peak cholesterol oxidase production (0.242 unit/ml) after 60-72 h cultivation was approx. 4-fold that in control medium.