AbstractFungal cells fromCurvularia lunatawere entrapped in a crosslinked polyacrylamide gel. The gel‐cells obtained as granules were applied in the microbial transformation of Reichstein compound S leading to cortisol through an 11‐β‐hydroxylation step. Some kinetic studies of this conversion using gel‐cells were carried out. In addition, it was shown that gel‐cell granules which had lost part of their 11‐β‐hydroxylase activity on storage could be reactivated yielding preparations with increased activity.FromCorynebacterium simplexa steroid dehydrogenase catalyzing the Δ1‐ dehydrogenation of cortisol leading to prednisolone was isolated and partially purified. The preparation was entrapped in a crosslinked polyacrylamide gel and the gel‐enzyme granules obtained used in steroid dehyd