Transformation of cortisol to prednisolone by viable cells of Arthrobacter simplex covalently immobilized on cellulose granules

Arthrobacter simplex cells have been covalently immobilized to granules of microcrystallized regenerated cellulose by means of N-hydroxymethyl, N′-glucosylurea groups at pH 8.5, 18°C and cell suspension concentration of 60 mg/ml. The immobilization yield was found to exceed 100%. The maximum initial rate of Cortisol transformation to Prednisolone remained almost constant after 20-fold transformation in a nutrient medium containing 0.5% peptone at pH 8.0, 32°C and aeration with oxygen. The effect of the substrate concentration on the activity of the immobilized cells, as well as of the ratio between substrate and immobilized cells on the degree of transformation, was investigated. The immobilized cells were characterized by means of electronmicroscopic studies. Microbiological observations have shown that immobilized cells can proliferate and the free cells obtained are accumulated in the nutrient medium. The immobilized cells preserve their viability for a long time when they are stored at 4°C.