Abstract
Two biological approaches have been investigated for specific modifications of steroids. The first one uses the purified enzyme for the specific dehydrogenation of androsterone to androstanedione. The enzyme used is 3α‐hydroxysteroid dehydrogenase which requires a cofactor (NAD). A cofactor regeneration is needed so that the process could work continuously. The conjugation of two points (immobilization of the enzyme and optimization of the ratio methanol‐water) allows a continuous work of the enzyme during 25 days. Moreover, we propose a chemical regeneration of the cofactor using methoxy derivative of phenazine methosulphate. Right now it is the limiting step of the process.
The second approach of steroid modification uses a whole mycelium of Aspergillus phoenicis for the specific hydroxylation of progesterone to 11α‐hydroxy progesterone. The transformation of 90% of the progesterone is obtained with calcium alginate immobilization and the lowest number of products is obtained at pH lower than 2.5 with carrageenan and polyurethane immobilization.
It seems promising to apply immobilized biocatalysts to the bioconversion of hydrophobic compounds in organic solvents system.