The use of Free and Immobilized Cells in the Presence of Organic Solvents: The Oxidation of Cholesterol by Nocardia Rhodochrous

  • J. M. C. Duarte
  • M. D. Lilly


We have been using Nocardia rhodochrous to oxidize cholesterol. Here we report the oxidation of cholesterol to cholestenone with free and immobilized cells induced for maximum cholesterol oxidase activity. Cholesterol, an almost water-insoluble substrate, is solubilized in a water-immiscible organic solvent. In such a heterogeneous system the reaction rates are dependent on several factors including the substrate concentrations, the amount of catalysts and the organic/aqueous ratio. Also the nature of the solvent can influence the observed rates by affecting the enzyme environment and/or the accessibilities of the substrates. Immobilized preparations have lower specific activities but retain their activities for longer than the free cells.


Immobilize Cell Heterogeneous Catalysis Free Cell Calcium Alginate Volumetric Rate 
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Copyright information

© Plenum Press, New York 1980

Authors and Affiliations

  • J. M. C. Duarte
    • 1
  • M. D. Lilly
    • 1
  1. 1.Department of Chemical and Biochemical EngineeringUniversity College LondonLondonUK

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