Cascade 2 - synthesis of ursodeoxycholic acid

The first step of this task comprises a highly selective dihydroxylation at the 12-position of naturally available cholic acid. In nature so-called dehydroxylases were identified that can carry out this transformation. This enzyme will be identified, expressed and characterized. In the second step, an isomerization will be carried out. 7a and 7b-Hydroxysteroid-dehydroge¬nases as immobilized cell-free enzymes carry out this step with high yields and selectivities. Co-immobilisation of these enzymes will be carried out in Pickering emulsions, possibly in combination with cross-linking. In the final stage of the cascade, compatibility of the two steps will be studied, taking into account the