Use of immobilized cells of Rhizopus nigricans for the 11α‐hydroxylation of progesterone

The filamentous fungus, Rhizopus nigricans, was immobilized in polyacrylamide, alginate, and agar gels and its ability to 11α‐hydroxylate progesterone was examined. No activity was detected using polyacrylamide gel but both agar and alginate gels have proved capable of hydroxylation. Agar gels displayed faster rates and higher yields. It was possible to induce hydroxylase synthesis within agar and alginate gels, and microscopical examination provided evidence for hyphal growth within these gels. The concept of increased biomass was used to explain the observed increase in the rates of hydroxylase activity of the immobilized cells. Conversely, hyphal overcrowding was postulated for the rapid inactivation observed under some operating conditions.