11α-Hydroxylation of progesterone by gel-entrapped living Rhizopus stolonifer mycelia

Spores of Rhizopus stolonifer were immobilized aseptically by entrapment with photo-crosslinkable resin prepolymers, urethane prepolymers or several kinds of polysaccharides. The entrapped spores were allowed to germinate and develop in situ. The immobilized living mycelia so obtained were induced for the steroid 11α-hydroxylation system and examined for their activity to hydroxylate progesterone at 11α-position in a buffer system containing 2.5% of organic cosolvent. Of various water-miscible organic cosolvents, methanol was found to be most effective in terms of the activity of the entrapped mycelia and the solubility of the product, 11α-hydroxyprogesterone. Though all the living mycelia entrapped in different gels exhibited the hydroxylation activity, mycelia entrapped in photo-crosslinked gels showed the maximum activity which was rather higher than that of the free mycelia. The net-work size of the photo-crosslinked resins, namely the chain length of the photo-crosslinkable resin prepolymers, affected markedly the mycelial growth in gels, and subsequently, the hydroxylation activity of the entrapped mycelia. Entrapment significantly enhanced the operational activity and stability of the 11α-hydroxylation system in the mycelia, and permitted the intermittent reactivation of the system by incubating the entrapped mycelia in potato-dextrose broth.