Immobilization of Bacillus pumilus E601 in poly(vinyl alcohol) (PVA) cryogels at a concentration of 10% grafted with hydroxyethylmethacrylate (HEMA) at a concentration of 0.4% using a radiation polymerization technique lead to an increase in the prednisolone yield (46%) compared with the prednisolone yield (38%) produced by immobilized B. pumilus E601 carrier on the surface of the polymer at the same concentrations. The Delta(-1)-dehydrogenase of B. pumilus E601 was affected by the molecular weight, the irradiation dose and the diameter of the polymer. The storage of immobilized B. pumilus E601 in poly(PVA)/HEMA at -4 degreesC for 30 days shows a higher yield of prednisolone (80%) as compared with prednisolone yield (75%) at 25 degreesC at the time of storage. (C) 2002 Elsevier Science Ltd. All rights reserved.