Abstract: In this study, Brevibacterium sp. was cultured in a fermentation medium supplemented with cholesterol to enhance the production of cholesterol oxidase. Through one-factor-at-a-time analysis, three experimental conditions including cholesterol and Tween-80 concentration in the fermentation medium and ultrasonic power (for promoting the release of intracellular cholesterol oxidase) were found to significantly influence the activity of crude cholesterol oxidase solution. The optimal cholesterol and Tween-80 concentration as well as ultrasonic power and treatment time were 3.30 g/L, 3.72 mL/L, 80 W and 20 min, respectively, as optimized using Box-Behnken experimental design and response surface methodology. The resulting cholesterol oxidase activity was 731.967 U/L, which was increased by 1.17-fold when compared with that obtained in the absence of cholesterol.

Key words: cholesterol oxidase, cholesterol, Tween-80, ultrasonic power