Production of cholesterol oxidase by Rhodococcus equi No. 23 in a jar fermenter

Rhodococcus equi No. 23 was grown in a batch fermenter. The effects of cultivation temperature, pH of the culture medium, aeration rate and agitation speed on the production of cholesterol oxidase (CholOx) by the test organism were examined. Results revealed that the cultivation temperature, the pH of the medium, the aeration rate and the agitation speed all affected the production of CholOx by R. equi No. 23. Adjusting the operation variables during the cultivation period increased the production of CholOx effectively and prevented the occurrence of overflow of foam during the fermentation period. A maximum CholOx activity of 0.34 unit/ml with a volumetric production rate of 0.011 unit/h per ml could be achieved in 30 h of cultivation at an aeration rate of 5.0 l/min, if the pH of the culture medium, the cultivation temperature and the agitation speed were controlled at 6.5, 39 degrees C and 200 rev. /min respectively during the first 24 h of cultivation, then shifted to 7.5, 37 degrees C and 300 rev./min respectively.