Resting cells of Rhodococcus sp. ATCC 39484 were immobilized in polyvinyl alcohol (PVA). The PVA-beads showed nitrile-hydrolysing activity with propionitrile as a model substrate. Drying of the beads resulted in a loss of weight of 85%. Re-swollen beads showed no loss in activity. In a continuously-operated fixed-bed bioreactor, beads were able to convert substrate concentrations up to 100 mM.